tangent
08-22-05, 16:39
Fungus in optical instruments.
Many old optical instruments have fungus growth on a glass surface. Fungus
does not look like haze but has an appearance like hairs or tendrils branching
from a center. While the fungus can be removed by cleaning, it frequently has
etched the glass, since fungi secrete enzymes and acids to chemically alter their
environment so they can absorb nutrients. This etching requires repolishing,
which if done unprofessionally will ruin the instrument. It is not possible to
tell if the glass is etched until the fungus is cleaned. Maintenance of optical
instruments involves prevention of future fungus problems, especially if located
in damp regions.
To sum up the lengthy documentation below:
--WWII research programs on fungus in optical instruments (Turner, below) used
sodium ethylmercurithiosalicylate, now known as Thimerosal and widely used
consumer medical products. When mixed in paint used inside the binocular, this
was found effective at preventing fungus. It is not known if Thimerosal is so
used today.
--Hydrogen peroxide, or bleach, can be used to kill fungus.
--Leitz documents describe a fungus treatment of 94% distilled water, 4% clear
ammonia (for cleansing) and 2% hydrogen peroxide (to kill fungus).
--Carl Zeiss Oberkochen, dept. KuDi, sells: Fungus Cleaning Agent
"Fungusreiniger NEU". Dilute with ethyl alchohol, leave on glass for one hour or
more, then clean. Not poisonous but avoid contact with skin. 100ml bottle, INR
0117.362 500ml bottle, INR 0117.361 1000ml bottle, INR 0117.360
--Notes on treatment & prevention are found at the end of this text.
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1. Turner, J.S., et al. Tropic-Proofing of Optical Instruments by a Fungicide.
Nature 158 (Oct. 5, 1946) 469-473.
2. Trokojus, V.M. Chemistry of Sodium Ethylmercurithiosalicylate. Nature 158
(Oct. 5, 1946) 473-474.
3. Fay, J.W.J. Comments. Nature 158 (Oct. 5, 1946) 474.
4. Saxena, B.B.L., S.S. Nigam, & S.R. Sengupta. Fungal Attack of Optical
Instruments & Its Prevention. Indian Journal of Technology 1 (1963) 283-286.
5. Horne, Douglas. Optical Production Technology. Bristol: Adam Hilger, 1972.
pp.50-51. Growth of fungus on lenses.
6. Yoder, Paul. Opto-Mechanical Systems Design. N.Y.: Marcel Dekker, 1993. p.60-
62. Fungus
7. Howard, Richard. The Role of Botanists During World War II in the Pacific
Theatre. page 100. Macleod, Roy, ed. Science and the Pacific War: science and
survival in the Pacific 1939-1945. Dordrecht: Kluwer, 2000.
8. Notes on fungus from military, commercial, camera, & optical sources.
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Tropic-Proofing of Optical Instruments by a Fungicide.
J.S. Turner, E.I. McLennan, J.S. Rogers, & E. Matthaei. University of Melbourne.
Nature 158 (Oct. 5, 1946) 469-473.
It is remarkable that the problem of the deterioration of optical instruments
by fungi has remained so long without thorough investigation. Until 1939 very few
people seem to have realized that fungi can grow actively on or over the internal
optics of binoculars, cameras, etc., exposed to warm and humid conditions. The
trouble became acute, however, in Australia when military units went into action
in New Guinea.
Not only were the facilities for storage of instruments extremely primitive in
the early stages of this campaign (1), but, as has since been shown, parts Of New
Guinea are climatically the worst possible Places for fungal troubles. In a short
time, the fungal infection of instruments designed for temperate regions became a
major problem. Optical instrument workshops, adequately equipped and staffed for
normal repair work, found themselves entirely unable to cope with the flood of
fungus-infected instruments which descended upon them. Many types of instruments
lasted only for four to eight weeks before infection; and, very often, new
instruments awaiting issue in depots were found to be deteriorating rapidly on the
shelves because of fungal attack. In fact, instruments in store were affected more
often than those in use, and the trouble was greatest where they were housed in
leather cases and stored in wooden boxes.
Accordingly, in 1943, the Australian Scientific Instrument and Optical Panel
(an advisory panel to the Ordnance Production Directorate of the Ministry of
Munitions, Australia) set up a special subcommittee, which carried out research on
this problem and which has issued interim reports from October 29, 1943, up to the
present time. (2) Considerable research was carried out during the same period in
both the United States (3) and Great Britain. (4) In this report we shall
summarize the results of the Australian work, which led to a reasonably effective
method of tropic-proofing optical instruments.
The fungi which grow in optical instruments belong to the groups Phycomycetes,
Ascomycetes and Fungi Imperfecti. The following species were frequently isolated
from instruments which had been in New Guinea: Penicillium spinulosum, Thom.; P.
commune, Thom.; P. citrinum, Thom.; Aspergillus niger, Van Tiegh.; Trichoderma
viride, Pers. ex-Fr.; Mucor racemosus, Fres.; and M. ramannianus, A. Moeller. So
far, Monilia crassa has not been isolated from Australian instruments, although
Dr. W. G. Hutchinson (5) of the United States, found this to be a common species
in the Panama zone, and it has also been recorded as frequent in West Africa by
Major I. G. Campbell. (6)
The fungal spores germinate on the moist surface of the glass lenses or prisms
or, more frequently, on particles of dust, luting wax, cork and other organic
debris. The mycelium spreads thence over the whole surface of the clean optical
glass. The moulds are particularly troublesome when they grow on graticules, but
they are also capable of obscuring lenses and prisms. The fine hyphal threads in
contact with the glass surfaces are often surrounded by minute condensed water
droplets or by droplets of alkali-soluble substances liberated from the glass
itself. If the mycelium remains for many months in contact with the glass, it is
capable of etching a pattern into it. More commonly, when removed, the mycelium.
leaves only a slight stain resembling an oil film which can be removed by cerium
oxide polishing.
The committee concentrated at first on methods for civilian binoculars which
were to be issued to the Australian Services. It was early decided that it would
be futile to attempt to desiccate these instruments or to ensure that they were
optically clean and sterile when dispatched. A search was made, therefore, for a
suitable volatile fungicide which could be placed in the instrument during its
first reservicing and fitting with graticules. The requirements of the fungicide
were: (a) toxicity to all possible contaminants, (b) action at a distance (that
is, volatility) for the substance could not be placed directly on the optics, (c)
stability in moist air and to a temperature of at least 60 degrees C., (d)
persistence of action over some months or, preferably, years, (e) lack of power to
corrode metals, especially brass, steel, and aluminium alloys, (f) non-toxicity to
man, (g) mite repellent (because mites have been shown to enter optical
instruments carrying fungal spores with them), (h) availability in war-time.
As might be expected, very few of the known fungicides passed even the first of
these tests. The initial laboratory experiment was designed to select a fungicide
with the properties noted in (a) and (b) above. For this purpose the substance
under test was incorporated in luting wax and a drop of this was melted on to a
microscope slide. This was then inverted and a hanging-drop culture of mixed
spores from optical instruments was set up around the wax.
The following known fungicides were shown to be ineffective under these
conditions for some or all of the moulds concerned: 'Ceresan', 'Agrosan',
'Shirlan', 8-hydroxy-quinoline, penta-brom-phenol, tetramethyl thiuram disulphide,
tri-brom-phenol, azo-chloranide, clove oil, copper naphthenate, phenyl mercuric
acetate, tri-oxy-methylene, methyl alcohol and thymol. Many other fungicides were
not tested here, following adverse reports on their properties from other workers,
for example, naphthalene, paraformaldehyde. Thymol was the most promising, but
further experiments with it were discontinued when it was found that an organic
mercurial completely suppressed the germination of all the species with which we
were concerned. This substance was sodium ethylmercurithiosalicylate, referred to
here as 'M.T.S.'. It had been produced in Australia on a large laboratory scale
by Prof. V. M. Trikojus and his associates of the Universities of Sydney and later
of Melbourne. It was in use by the Australian Army Medical Corps for the
preservation of blood. Prof. Trikojus suggested its trial for tropic proofing, and
very, extensive tests have shown it to be the best fungicide so far investigated
by us for this particular purpose.
At first, the M.T.S. was incorporated only into luting waxes, but later it was
mixed with a black lacquer, which was used to cover the interior metal surfaces of
optical instruments. It was mixed with this paint to give a concentration of 0.2
per cent in the liquid and it was also incorporated in the microcrystalline wax
which we used for luting purposes. Our experiments show that the dry M.T.S., pure
or in paint, is scarcely volatile at all, but in the presence of water vapour it
is decomposed, probably by hydrolysis, to give a very active fungicidal and
fungistatic vapour.
Following hanging-drop tests, binoculars and rangefinders were painted
internally with the poisoned lacquer and mixed fungal spores were dusted on thin
agar films with which the optics had been coated. The instruments were then
assembled in the normal way and placed in a tropic-proofing test cabinet under
conditions of high humidities and temperatures. Some of the instruments were also
wrapped in damp calico which had been sprinkled with spores, and living mites were
introduced into the cabinets. Under these conditions, no fungal growth occurred
inside the treated instruments, but there was abundant growth in the control
instruments which had not been poisoned. In later experiments, cylindrical tins of
300 cubic cm. capacity were painted internally with black lacquer, some of which
had been poisoned with M.T.S. or with its butyl or methyl esters, in
concentrations of 0.2 per cent. The space inside was saturated with water vapour,
and each tin contained, for the actual test, a microscope slide covered with a
film of nutrient agar and dusted with fungal spores. In no instances have spores
germinated in tins containing the M.T.S. poisoned paint, although some of these
tests were carried out six months after the paint had been applied to tins open to
the atmosphere through minute holes. The vapour arising from the M.T.S. paint has
been shown to kill the spores as well as to inhibit their growth. Further
experiments, carried out by an officer of the Victorian Department of Agriculture,
have shown that the vapour arising from the hydrolysis of M.T.S. is lethal to
mites, but it does not act as a mite repellent. This corresponds with our own
experience ; and we have found that, while mites entering M.T.S. treated
instruments are killed, their bodies do not then act as centres for the growth of
fungi.
In the experiments with closed tins referred to above, some germination of
spores did take place when the paint contained either the butyl or the rnethyl
ester of M.T.S., but only when the tins had previously been stored for six months.
The methyl ester was the less promising, but Dr. Hutchinson, of the United States,
has informed us that the butyl ester which we supplied to him was rather more
effective than M.T.S. itself in his Panama Zone experiments. This ester has the
advantage of being soluble in lipoid solvents, and further trial may prove it to
be a fungicide of better value than the sodium salt (M.T.S.) itself.
Once the value of M.T.S. as a fungicide was established, it became necessary to
test its corrosive power. The first results were most discouraging, as it was
found that aqueous solutions of M.T.S., both in the acid form and as the sodium,
copper and zinc salts, brought about rapid accelerated corrosion of aluminium and
some slight corrosion of brass. The corrosion was of a type which suggested that
free mercury ions were released in solution and catalysed the reaction. However,
it has since been found that when incorporated in a suitable lacquer, the M.T.S.
causes no corrosion at all of the metal under the lacquer or of unpainted damp
metal surfaces near by, even when the test piece is enclosed in a small volume of
warm, damp air. On the contrary, the layer of lacquer protects the metal surfaces
against the action of water vapour, which is known to cause extensive corrosion in
optical instruments exposed to tropical conditions. So far as experiments have
gone, there is no evidence that M.T.S. attacks lens cements (balsam or n-butyl
methacrylate), nor does it cause the filming of optics.
This lack of corrosion by M.T.S. in paint may have been due in part to the
special properties of the paint we employed. We have recommended the use of a
nitro-cellulose lacquer which dries quickly to a reasonably matt surface. It is
manufactured by B.A.L.M. under the name of 'Duco Enamel Lacquer'. Recent reports
from England indicate that other lacquers are not necessarily suitable. We have
also found it not advisable, from the point of view of corrosion, to incorporate
the M.T.S. into the zinc oxide-retinax grease used as a lubricant for eyepiece
threads. It should be noted here that the M.T.S. makes up 0.2 per cent of the
liquid lacquer; when this dries put, the mercurial poison is dispersed in the film
at a concentration approaching 0.8 per cent.
Our corrosion tests are supplemented by observations on binoculars which have
been tropic-proofed with M.T.S. and exposed for long periods as follows: 1- some
instruments were kept for three months in the laboratory in Melbourne; 2- others
were exposed for two months in a test chamber to 100 per cent relative humidity
and 30 degrees C.; 3- about thirty instruments were exposed to tropical conditions
in New Guinea for two and a half months and then returned to Melbourne for
examination.
Corrosion in all these instruments was limited to that taking place on exposed
aluminium alloy surfaces and its extent was that which would be expected, from
control experiments, to occur whether M.T.S. was present or not. Experiments at
the Munitions Supply Laboratories, Maribyrnong, have also shown that black lacquer
containing 0.2 per cent M.T.S. does not cause 'season cracking' of brass. Finally,
although many thousands of optical instruments have now been tropic-proofed in the
way recommended, there has been no report from the Services of corrosion in these
instruments.
These tests and observations have convinced us that there is very little danger
of corrosion by M.T.S. in paint. They have, at the same time, led us to recommend
that all internal metallic surfaces of optical instruments for tropic use should
be painted or anodized so as to render corrosion by water vapour negligible.
Since 1943, numerous field experiments in New Guinea have confirmed the value
of M.T.S. as a fungicide in optical munitions. A short test in 1944 with thirty-
four binoculars in stores at Milne Bay, Lae and Port Moresby was inconclusive in
that many of the control instruments did not become infected. However, at Lae,
four binoculars containing M.T.S. remained free from infection on all optics,
while two untreated instruments were all infected on various optical surfaces.
Later, twenty binoculars and six rangefinders were exposed in Kunai grass near
the jungle for six months and then returned to Melbourne for examination. One side
of each of the binoculars was tropic-treated, while the other side acted as
control. Three rangefinders were treated and three acted as control. After six
months, there was no infection in any of the treated sides of the binoculars,
except for one slight trace of non-sporing fungus on one prism. Practically all
the untreated sides were infected, some badly. All three treated range-finders
were free of fungus, while all the untreated instruments were badly infected. This
is a striking proof of the efficacy of M.T.S., as the rangefinders are badly
sealed instruments and yet even in these the fungicide retained its activity.
A long-term experiment has just been started in New Britain. One hundred
instruments (binoculars) have been assembled with exactly the same luting, lacquer
and eyepiece grease; but on one side of each instrument the lacquer and luting
contain M.T.S., while the other side is free of this substance. Twenty-five pairs
are to be returned to Melbourne at six-month intervals for examination. The
efficacy of the fungicide will thus be tested over a period if two years.
Three pairs of binoculars treated with M.T.S. in Melbourne have been exposed to
tropical conditions in the Panama zone. They are still under test, but they have
so far remained free of fungus for a period of five months.
Perhaps the most striking evidence in favour of M.T.S. is its control of fungal
infection in aircraft cameras, which are, of course, badly sealed instruments. At
the beginning of 1944, the secretary of the Scientific Instrument and Optical
Panel was approached by an officer of a camera repair unit of the U.S.A.A.F., who
reported very severe damage to aircraft cameras caused by fungi.. The unit adopted
the M.T.S. treatment for all its cameras and has reported that none of the 350
cameras so treated became infected during a period when approximately a hundred
lenses, including fifty from aircraft cameras, were returned for the removal of
fungi from the optics. One aircraft camera, treated with M.T.S., has remained
internally free of fungus for a period of twelve months, although, on occasion,
fungi have had to be wiped off the external lens faces. Officers of this unit have
also found that the growth of fungus in fibre cases for carrying cameras could be
prevented by coating the cases internally with black lacquer containing M.T.S.
The Australian Military Forces adopted the M.T.S. treatment in 1944, and all
types of optical instruments manufactured or assembled in Australia, including
thousands of binoculars, have been treated in this way. The R.A.A.F. and one
section of the U.S.A.A.F have also adopted the method, as has the Royal Australian
Navy. Recent reports from Britain indicate that the method is undergoing tests by
the R.A.F., although it is there recommended that internal metal surfaces should
be anodized or covered with a primer before the poison lacquer is applied.
In aqueous solution M.T.S. will prevent the growth of Penicillium at
concentrations so low as 1 in 2millions. It is used locally in 1 in 1,000
solution, as a tincture for skin disinfection and as a nasal spray, and it has
also proved of value for preserving blood serum. (7) It is regarded as most
unlikely to cause any harm to man in the concentrations recommended for tropic
proofing, as the lethal dose for man is believed to be about 1,000 milligrams. Its
action at a distance is best shown as follows. Black paint containing 0.2 per
cent M.T.S. is used to coat glass plates approximately 4 in. square; the painted
surface is then apposed to a similar plate coated with thin agar dusted richly
with Penicillium spores. The two plates are kept 2 mm. apart by spacing strips
round the edges. No spores germinate (in fact they are killed) on the agar when
the two plates are incubated under humid conditions. If, however, the paint is
applied in two narrow bands forming a cross, spores do germinate to form a thin
mycelium, but only in the corners of the plate. The mycelium then slowly spreads
towards the middle where the concentration of toxic vapour is at the maximum.
Under these conditions it appears that mutual reaction between the fungus and the
vapour keeps the concentration down and allows slowly continued growth of
mycelium. The vapour (which presumably contains a mercury compound) takes effect
whether the paint lies above or below the agar; but in some experiments it was
noticed that the inhibition of growth on plates held vertical was exerted over a
greater distance on the lower sides of horizontal painted bands.
Incorporated into paints, M.T.S. may prove to be a useful fungicide apart from
its application to optical munitions. For example, Mr. P. G. Law has suggested its
use as a preventive of mould spotting in framed prints. Preliminary tests indicate
that, if the wooden back of a picture frame is painted with M.T.S. lacquer on the
side facing the print, mould growth in humid atmospheres is prevented. Technical
officers in museums and galleries may find that further investigation along these
lines is worth while.
The authors desire to acknowledge the valuable assistance of the other members
of the Scientific Instrument and Optical Panel committee: Mr. P. G. Law, Mr. J. W.
Blamey, of the University of Melbourne; Mr. G. C. Wade, of the Victorian
Department of Agriculture. Our thanks are also due to Prof. V.M. Trikojus, Mr.
G.M. Willis of the Metallurgical Department, University of Melbourne, Mr. M. Pack
of B.A.L.M. and several officers of the Munitions Supply Laboratories, who all
made contributions towards the solution of the problem. The Tropical Scientific
Section of the Scientific Liaison Bureau, Melbourne, rendered assistance in the
carrying out of the field tests in -New Guinea.
Footnotes.
1. Scientific Liaison Bureau, Australia. "Report on the condition of Service
Material under tropical conditions in New Guinea." Restricted. October 21, 1943.
2. Scientific Instrument and Optical Panel, Ministry of Munitions, Australia.
"The Tropic Proofing of Optical Instruments, Part I", July 1944.
3. O.S.R.D. Reports, U.S.A., No. 1833, July 1943. No. 4188, September 1944.
4. Reports of Optical Instruments Panel of Conference on Tropic Proofing,
Controller of Chemical Research and Development, Ministry of Supply, Great
Britain, papers issued under MG/OPT.
5. Hutchinson, W. G., in O.S.R.D. Report No. 1833, July 1943.
6. Campbell, Major I. G., "Fungi in Optical Instruments under Tropical
Conditions, and Possible Control", D.M.E. War Office, Great Britain, December
1944.
7. Simmons, R. T., and Woods, E. F., Austr. J. Sci. 8 (1946) 108.
--------------------------------------
Chemistry of Sodium Ethylmercurithiosalicylate.
Prof. V.M. Trokojus, University of Melbourne.
Nature 158 (Oct. 5, 1946) 473-474.
Sodium thylmercurithiosalicylate is a white crystalline solid, melting at about
230 degrees C. and easily soluble in water and the lower alcohols, but insoluble
in lipoid solvents. Its preparation -was first reported by Kharasch in 1928 (8)
(cf. also Waldo (9)).
In the manufacture of the drug in Australia for plasma preservation and tropic-
proofing, undertaken initially by J. E. Falk and since, in larger quantities, by
R. H. Hackman, ethylmercuribromide was condensed with thiosalicylic acid (15 per
cent excess) in aqueous-ethanol with the equivalent of 2-5 mol. sodium hydroxide.
About a kilogram of thiosalicylic acid was used per batch. The crude
ethylmercurithiosalicylic acid (by precipitation with hydrochloric acid) was
purified by recrystallizing <section cut>
Both compounds are insoluble in water but readily soluble in lipoid solvents,
an obvious advantage when applying the materials to paints and lacquers; moreover,
the methyl ester can be obtained in a pure condition much more conveniently than
the sodium salt.
The action mechanism of the sodium salt as a fungistatic and fungicidal agent
is uncertain. It has been proved to act at a distance, but it is improbable that
a sodium salt of this configuration would possess a significant vapour pressure.
Kharasch has pointed out that aqueous solutions of the sodium salt tend to break
down to ethylmercurihydroxide (III) and sodium thiosalicylate, the latter, in the
presence of oxygen, passing irreversibly to the dithiosalicylate (IV). Thus the
access of water vapour, providing conditions for fungal growth, might also favour
a similar breakdown of the lacquer-incorporated mercurial, or even further to more
volatile substances.
Footnotes.
8. Kharasch, M.S. U.S.P. 1 (1928) 672, 615.
9. Waldo. Journal Amer. Chem. Soc. 53 (1931) 993.
---------------------------
Comments by Dr. J.W.J. Fay, Ministry of Supply.
Nature 158 (Oct. 5, 1946) 474.
I am glad to have seen these two interesting papers, and take the opportunity
of offering the following comments on British experience.
Two factors have militated against the use in Britain of M.T.S. on other than
an experimental scale.
First, in the design of new instruments, or the modification of old types, the
tendency has throughout been towards the improvement of sealing and of packaging.
This, coupled with the use, if necessary, of a desiccating agent, is considered
the ideal at which to aim, since the need of a fungicide is eliminated.
Secondly, in connexion with the protection of old instruments, including ex-
civilian surrendered types of unknown history, the incorporation of volatile
fungicides was not without its dangers. Thus, various substances tried gave rise
to such troubles as softening of cements, corrosion and filming. Nevertheless, the
need for a suitable fungicide was recognized and many were tested.
Among these, M.T.S., of which the vapour pressure is extremely low, was found
to depend for its action upon a decomposition in the presence of moisture, giving
rise to a volatile mercury compound which is presumably the active agent. The
decomposition was found to be accompanied by a corrosion danger, and in the
lacquers we have used this danger has not yet been overcome. We are, however, now
awaiting samples of Australian lacquer for test.
In general, therefore, even in the case of old-type instruments, our attitude
has been to improve sealing and methods of servicing, packing and storing, and the
tendency is in any case to regard the incorporation of a desiccant as preferable
to the use of fungicides.
With reference to the New Guinea experiments, we have had the opportunity of
examining a few of the instruments tested, and our view is that while the results
afford evidence of the superiority of the new complete Australian 'tropical
treated' method over the old one, it is not entirely clear, in the absence of true
controls, how much of the improvement is to be ascribed to the use of M.T.S. For
this reason, we shall look forward with great interest to the results of the long-
term New Britain experiments in which rigid controls are apparently included.
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Saxena, B.B.L., S.S. Nigam, & S.R. Sengupta. Defence Research Laboratory
(Stores), Kanpur.
Fungal Attack of Optical Instruments & Its Prevention.
Paper presented at the Symposium on Instruments, held at TDE (Instruments), Dehra
Dun, in November 1959.
Indian Journal of Technology 1 (1963) 283-286.
The nature and pattern of fungus infestation on various components of
binoculars in hot, humid conditions (Calcutta, Cochin and Bombay) have been
investigated. The organisms isolated and identified include: Aspergillus niger, A.
fumigatus, A. candidus, Penicillium sp., Paecilomyces sp., Syncephalastrum sp.,
Sepedonium sp., Curvularia sp., Fusarium sp., Monilia sp. and Cladosporium sp.
Prisms and OG lenses show greater fungal infestation than FL or EL lenses;
graticules and lutings show slight to moderate degree of incidence. Protective
treatments tried on brass and aluminium materials indicate that satisfactory
protection is provided by: 1- incorporating fungicides like Cresatin, Merthiosol,
copper naphthenate and pentachlorophenol in lacquers, varnishes, lutings, waxes,
greases and paints applied to various components of the instrument; or 2-
depositing on the surface, coating compositions containing suitable fungicides by
chemical or electrolytic methods.
In tropical climate characterized by high temperature and humidity accompanied
by nocturnal condensation, optical instruments are prone to fungal attack during
storage. Instruments such as binoculars, rangefinders, telescopes, cameras and
similar other equipment lose their functional efficiency when they are attacked by
fungi and thus cause considerable financial loss. Although as early as 1932, the
fouling of binoculars by fungi was recorded in India (1), it was not until 1939
that it was realized that fungi can grow actively on glasses, prisms of binoculars
and on lenses of cameras. (2) In 1943, it was reported from New Guinea that the
presence of fungal colonies in optical equipment was the 'rule rather than the
exception'. (3) Under favourable conditions, fungal infestation is not confined
to a specific component of an optical instrument but spreads to all the parts.
Optical glasses, prisms, lutings, seals, greases, waxes, lacquers and varnish
coatings are all attacked, pointing to the need for an overall improvement in
materials used in the fabrication of optical instruments.
Workers in India were among the first to identify the actual nature of the
microorganisms responsible for the unserviceability of optical instruments. In
1940, at Rawalpindi arsenal the use of desiccating valves fitted to binoculars as
a means of reducing the fouling was resorted to. Work was simultaneously carried
out in the USA, the UK, Canada and Australia to study the nature of deterioration
of optical instruments and also to study the behaviour of a large number of tropic
proofing compounds. In 1943, Hutchinson (4) examined a large number of optical
instruments and recommended the use of 'Cresatin' (m-cresol acetate). In 1944,
Campbell carried out large-scale investigations (5) in order to develop antifungal
as well as antifilming measures for use in the Service equipment under jungle
conditions of storage and usage. In the same year similar type of work was done in
Australia. In India, at the then Inspectorate of Scientific Stores (Instruments
and Electronics), Calcutta, work was carried out on the problem of fogging,
filming and fungal infestation of optical instruments. In collaboration with that
organization, Defence Research Laboratory (Stores), Kanpur (then known as Ordnance
Laboratories), investigated the nature and extent of microbial damage in
binoculars. In 1945, the Directorate of Armaments (India) carried out extensive
exposure trials at Calcutta and later in 1948 at Cochin and Colaba (Bombay). These
trials were on different types of optical instruments and consisted in subjecting
them to adverse storage conditions.
Failure of Optical Instruments
The failure of optical instruments in the tropical regions may be due to
fogging, filming or fungus infestation. In addition, corrosion of metallic parts
of binoculars has also been noted. Fogging involves the occurrence of moisture
droplets on glass surface due to condensation of moisture from the atmosphere. It
is transient and depends solely on the atmospheric humidity of the place. Filming
involves the production of a greyish coating on the optical surface and it is
progressive and not transient. When condensation / fogging occurs on the optical
surfaces, free alkali which is present on the surface of the glass goes into
solution. This alkaline solution reacts with the carbon dioxide of the air and
forms a solution of alkali carbonate. When the instrument gets dry, the solution
evaporates and leaves carbonate crystals on the glass surface. Thus, a permanent
film is left on the glass surface. Filming is also caused by the condensation of
volatile constituents of eyepiece lubricants and sealing materials. Among the
optical instruments, binoculars are most prone to the development of moulds. In
other instruments, too, the liability to mould growth is favoured by openness of
construction, i.e. whether or not the instrument has focussing eyepieces or
bodies, adjustment and apertures or 'breaks' due to rotating mechanism. Even
sealing compounds aid in the development of moulds.
The fungal spores germinate on the moist surface of the glass lenses or prisms
or more frequently on particles of dust, luting, wax, cork and any organic debris.
The mycelium spreads thence over the whole surface of optical glass. The fungi are
particularly troublesome when they grow on the graticules. They are also capable
of obscuring lenses and prisms. Fungi grow well on the outside of the object
glasses and more so when the instruments are stored in mouldy cases. By far the
most important source of fungi found within optical instruments or on the exterior
is the mouldy case of the instrument.
The present communication presents the results of a preliminary study on the
isolation and identification of fungi from a few typical affected pieces of
binoculars. The use of certain protective agents has also been investigated.
Experimental Procedure
The binoculars received from the Inspectorate of Scientific Stores, Calcutta,
and from the Technical Development Establishment (I & E), Dehra Dun, after
exposure trials at Cochin and Colaba, were examined for the nature and pattern of
fungal attack on the various components. Cultural studies of the fungal growth on
glasses, prisms and graticules were also made.
Visual and microscopic examination: Fungal infection was observed in varying
degrees on different parts of the binoculars. The lenses and prisms were most
affected, followed by graticules, lutings and greases. Even the paint was attacked
by fungi. In some cases the fungus growth had etched the glass. Wherever dead
mites, debris or grit were found, fungal growth was luxuriant. The mycelium
branched profusely, often forming a dense compact mass bearing spores (Fig. 1).
When the food material was not in abundance, the growth on most of the prisms was
restricted to a very few delicate branched hyphae bearing occasionally few spores.
In extreme cases, where the growth was exclusively at the expense of the food
material present in the spore, the mycelium consisted of a few rudimentary hyphae
radiating from the spore in the form of a star (Fig. 2). When the growth of a
fungus started from the central region of the flat surface as in OG lens, it was
usually symmetrical in all directions (Fig. 3); and when the amount of food
material was abundant the growth was dense and spread out irrespective of the
species (Fig. 4).
In some cases, as a result of fungal action, luting and organic debris
partially dissolved in the condensed water vapour and spread out along hyphae
producing irregular opaque configuration, thereby interfering with light
transmissions (Fig. 5). In prisms, the growth started from the apex and radiated
on the two surfaces forming irregular ramifications. In some cases, the hyphae
branched profusely and were often enveloped with droplets of water throughout
their length, thereby causing fogging of the instrument (Fig. 6).
The patterns of fungal infection of lenses and prisms of binoculars can be
considered to belong to the following types: 1- A spidery fungal growth radiating
from a central point. The fungal growth is easily removable and does not etch the
glass surface. Chlamydospores are often found and conidiophores when produced may
bear only a few chains of spores. 2- 'Starfish' type, in which the growth is
flat, adhering closely to the glass like a thick whitish drop and on removal
leaves the colour on the glass. The growth is composed of fragmented hyphae
surrounded by droplets of water. 3- Minute circular spots which always etch the
glass. They consist of tiny fungal colonies on small particles.
Isolation of fungi: The following methods were adopted for the isolation of
fungi from the infected components of the binoculars: 1- The prisms were placed
in Petri dishes containing potato-dextrose agar (PDA) medium. After incubation for
a week at 30 degrees, plus or minus 2 degrees C, subculturing was done of the
fungi which were found growing. 2- A scraping of lacquer / varnish from the
inside of the binocular was obtained and the scraping was planted on PDA medium.
3- Tube culturing was done by placing a drop of sugar solution on the lens over
the fungus to be examined, and transferring with a platinum loop, after gentle
rubbing, to the surface of a PDA slant. These slants were incubated at 30 degrees,
plus or minus 2 degrees C, for a week and the organisms isolated. 4- Infected
lenses and prisms of binoculars were washed with sterile distilled water under
aseptic conditions and the surface growth was removed with small pieces of sterile
filter paper. These pieces were then plated out in Petri dishes with a small
quantity of water on Waksman medium. These Petri dishes were incubated at 30
degrees plus or minus 2 degrees C. for a week and the organisms isolated.
Nature, incidence and frequency of fungi: The fungi growing on optical
instruments belong to Phycomycetes, Ascomycetes and Fungi Imperfecti (2). Most of
the isolates from the binoculars were identified as common fungi. Similar types
have also been reported from Australia (2). The common types isolated belong to
Aspergillus and Penicillium groups. In some cases, due to prolonged desiccation
and unfavourable conditions hyphae and spores (observed under microscope) failed
to grow on the medium. The following fungi were isolated from the various
components of the binoculars: Aspergillus niger, A. fumigatus, A. candidus,
Penicillium sp., Paecilomyces sp., Syncephalastrum sp., Sepedonium sp., Cuvulvaria
sp., Fusarium sp., Monilia sp. and Cladosporium sp.
Along with fungi, bacteria and a few yeast cells were observed. Some of the
bacteria were chromogenic. Prisms and OG lenses showed greater fungal infection
than FL or EL lenses. Graticules and luting showed slight to moderate degree of
incidence.
Protective Treatments
Since moisture is the chief cause of fogging, filming and fungus growth, it is
imperative to prevent ingress of moisture into the instruments. Several methods of
controlling fungus fouling of optical surfaces have been reported, such as
sanitation (6), dehumidification (1), use of antidimming substances (unpublished
data from Defence Research Laboratory (Stores), Kanpur), and fungicides.
As part of the present study, the suitability and efficiency of several
fungicides when incorporated in lacquers, varnishes, luting, waxes, greases and
paints against fungal attack were investigated. The application of coatings (by
chemical / electrolytic methods) for the protection of metal against corrosion and
fungal attack was also investigated.
Lacquers: Nitrocellulose lacquer, cashew nut shell lacquer (CNSL), and BALM
Duco lacquer containing Cresatin (0.5 per cent), Merthiosol (0.34 per cent),
copper naphthenate (3.0 per cent) and pentachlorophenol (PCP) (1.0 per cent) as
fungicides were tested. It was found that: 1- CNSL is less susceptible than
nitrocellulose lacquer, 2- lacquers containing Cresatin, Merthiosol and PCP (1.0
per cent) are ineffective, and 3- matt-pigmented CNS lacquer with 2 and 3 per cent
PCP is effective. BALM Duco lacquer is also slightly susceptible to mould attack.
Varnishes: Matt-pigmented oil varnish black DTD 34, air-dried or stoved at 120
degrees C. for 4 hours and containing PCP Merthiosol and castor oil distillate,
were tested. It was found that: 1- stove-drying does not give satisfactory
results, and 2- matt-pigmented oil varnish (air-dried) with PCP (3-0 per cent) is
effective. Other treatments were unsatisfactory.
Luting, waxes and greases: Incorporation of PCP (1.0 per cent) in these
materials conferred resistance to mould attack.
Paints: Silicone paint aluminium (air-dried) and silicone paint yellow type
(stoved) were found to be susceptible to mildew attack.
Protective coatings: Experiments were carried out to find out suitable methods
by which protective coatings can be obtained by chemical or electrolytic action on
brass and aluminium. For brass, two methods were adopted successfully. In the
first method, the blackening was carried out by immersion of polished brass in a
cuprammonium bath containing copper carbonate and ammonium chloride and treated
with 0.2 per cent PCP, while the second method involved anodic oxidation of brass
in a caustic soda bath and treatment with 0.2 per cent PCP. In the case of
aluminium, the blackening was carried out by anodizing the aluminium and then
dyeing it with organic black dyes / black inorganic pigment. The panels were
treated with 0.2 and 0.4 per cent PCP.
The blackened brass and aluminium pieces were subjected to fungal growth test.
The results indicated that the above protective coatings are effective against
fungal growth. Matt finish is also adequately protective as compared to that
produced by BALM Duco lacquer containing Merthiosol.
Confirmatory trials based on the above findings were made with aluminium tubes.
The tubes were anodized, dyed and then treated with PCP in the same bath. The dye
concentration was 1.0 per cent and that of PCP 0.2 or 0.5 per cent. These were
also found resistant to fungal attack. These results indicate that the application
of a protective coating with a fungicide can provide satisfactory protection
against fungal attack. In the absence of indigenous production of synthetic
resins, coating with the fungicides by chemical or electrolytic methods seems to
be the best solution of the problem. Another advantage of coating the surface in
this manner would be that by eliminating solvents, the residual solvent effect in
producing fogging is overcome.
Acknowledgement
Grateful acknowledgement is made to the Paints and Physical Chemistry Groups of
this laboratory for the supply of different paints, varnishes and lacquers as well
as anodized metal components for microbiological assay. The authors are indebted
to Shri S.K. Ranganathan, Ex-Control Officer, Biological Branch of this
laboratory, for help and guidance in the preparation of this paper.
References
1. Rao, C.S., Tropic Proofing trials on optical instruments. (TDE, Instruments &
Electronics, Dehra Dun), 1947-48.
2. Turner, J.S., et al. Nature, Lond., 158 (1946), 469.
3. Magee, C.J. et al. Report on the condition of service material under tropic
condition in New Guinea (Scientific Liaison Bureau, Australia), 1943.
4. NDRC Communication No. SR/7/43/9032, 27 July 1943.
5. Campbell, I.G. Report on the development of fungus fogging and filming in
optical instruments under tropical condition, and possible control (Director of
Mechanical Engineering War Office, Great Britain), 1944.
6. OSRD Rep. No. 4118 (University of Pennsylvania, 1944.
================================================== =====================
Horne, Douglas. Optical Production Technology. Bristol: Adam Hilger, 1972. pp.50-51.
2.23 Growth of fungus on lenses.
Fungal growth on optical components in the tropics has been a problem for many
years, and there is no evidence that any of the thin film coatings are a deterrent
to the mycelia attacking the glass. Attempts to clean glass surfaces after they
have been contaminated by mould will fail, as the glass itself will have been
damaged, and prevention of the mould growth is the only effective cure to the
problem. The damage to the glass surface usually takes the form of a general
'greyness' so that the light passing through is diffusely scattered. This leads to
a reduction of contrast and 'veiling glare' and if the surface lies on a graticule
in the focal plane of an eyepiece system the damage becomes very noticeable.
Even if the air inside instruments is desiccated immediately after initial
cleaning and assembly, and then sealed in a suitable package, deterioration often
occurs. The main causes of deterioration, in addition to fungus growth, are
attacks by water vapour and from the vapours of lubricants and optical cements
used in the instrument.
Under tropical conditions once a certain level of internal humidity has been
reached the daily range of ambient temperature may cause alternate condensation
and evaporation of water on the surface of the glass. The material dissolved out
of the surface is precipitated during evaporation and forms an alkaline solution
on the following condensation which further hastens the attack.
Where volatile machining fluids have been used during manufacture 'filming' may
occur unless the instrument parts have been very carefully cleaned before
assembly, and subsequently desiccated in a vacuum.
The natural grease of the hands may be found in polishing cloths which have not
been chemically cleaned and can cause 'films' to form on glass surfaces.
Certain types of brass which are often used in graticule or lens mounts may
contain free lead, which is readily soluble in water, and can creep or diffuse
from adjacent metal surfaces on to the surface of the glass and cause
deterioration under variable temperature conditions.
Most fungal damage arises during storage, and silica-gel bags will reduce the
ambient humidity and so make attack less likely. Sealing of the optical parts is
usually impossible owing to the need to maintain relative movements of parts for
focusing or rotation, as in theodolites or other surveying instruments.
If photographic lenses can be sealed, a clear metal lacquer containing 5%
salicylanalide (based on non-volatile content) can be used as a fungicide sealant.
The general approach is to introduce a fungicide which is relatively non-
volatile but still adequately lethal. Phenylmercuric acetate and Merthiosal (MTS)
are used with some success. All fungicides at present in use:
(a) Are toxic to humans.
(b) Cause condensation on glass surfaces.
(c) Have a deleterious effect on optical cements.
(d) Tend to produce dermatitis.
(e) Corrode metal parts, particularly aluminium alloys.
=================================================
Yoder, Paul. Opto-Mechanical Systems Design. N.Y.: Marcel Dekker, 1993.
p.60-62. Fungus
When glass components in optical instruments such as telescopes, binoculars,
cameras, and microscopes are exposed for long periods to warmth and high humidity,
films and localized deposits of mold may develop. Particularly troublesome in
tropical climates, these organic contaminants degrade performance by introducing
scatter at early stages of development (Rodionova et al., 1972); later they may
permanently damage optical surfaces by etching patterns into the material.
Baker (1969) provided a bibliography of 51 articles and papers published between
1941 and 1969 on the general subject of "tropic proofing" optical instruments.
Mold fungi have been found to germinate and grow on glass surfaces even though the
surfaces had been thoroughly cleaned to remove fingerprints, dust particles, and
lubricants (Theden and Kerner-Gang, 1965). The microscopic spores are ubiquitous
and seem to be able to supply sufficient nutrients internally to support limited
growth. Some glasses with high resistance to climate and acid seem to resist
fungus as well. Others (such as KzFS4) seem to impede mold growth, at least at
high humidity levels, although they are otherwise susceptible to climatic and acid
conditions. This contradictory behavior indicates that the chemical composition of
the glass plays a role in mold susceptibility.
Sprouse and Lawson (1974) reported evidence from tests conducted in the tropics
(Panama Canal region) to the effect that natural organic compounds condensed on
surfaces of glass and steel could serve as nutrient sources for fungal growth. It
was thought that, in the tropics, organic compounds (hydrocarbons) could come from
vegetation effluents. Monoterpenes (empirical formula C10 H16) previously thought
to play a role in tropical fungal accumulation were not found in any significant
quantity in the tropical atmosphere sampled. An aliphatic ester common to certain
tropical grasses was found to be present in significant quantity in that
atmosphere.
Baker (1967) evaluated some fungicides as mold preventive agents on optics. Later,
he described possible adverse effects of two fungicides (Baker, 1968). Baigozhin
et al. (1977) reported experiments with some chemically unstable optical glasses
that had been protected by fungicidal coatings that did not alter the glasses
optical properties. Optics protected with silicone films containing arsenic,
mercury, or tin resisted fungus tests for 3 to 4 months, whereas unprotected
optics of the same glasses were overgrown with fungus within 1 month of the same
test.
Harris and Towch (1989) described a series of environmental tests conducted on
several types of infrared windows intended for use in FLIR systems. They included
mold growth in this program, expecting to find the materials to be impervious to
this damage hazard. After 28 days, the test results indicated that a zinc sulfide
sample had lost most of its rain-resistant coating while a monocrystalline
germanium window showed coating damage. Transmission losses for these samples
exceeded what would be expected if the coatings were completely removed. Similar
control samples did not incur any damage or transmission loss so the degradation
was attributed to the effects of mold.
Baker, P.W. An Evaluation of Some fungicides for Optical Instruments. Int.
Biodeterioration Bull. 3:59, 1967.
Baker, P.W. Bibliography on Tropic Proofing of Optical Instruments. Royal Radar
Establishment Tech. Note 747. Malvern, England. 1969.
Theden, G. & W. Kerner-Gang. Results of Investigations on the Contamination of
Optical Glass by Fungi. (Glastec. Ber. 37:200, 1964). Translation, U.S. Defense
Documentation Ctr., Document AD458907, 1965.
================================================== ======================
"In Canada, mycologists of the Division of Botany of Agriculture developed
'Tropic proofing for war equipment', especially methods of preventing etching of
the optics of binoculars and riflescopes. (D.B.O. Saville ex W.L. Minshall,
personal communication, 16 July 1992)"
"In Australia, several organizations paid attention to problems of tropical
deterioration affecting optical equipment. (1: Report on Tropic Proofing of
Optical Instruments. Optical Munitions Panel Paper No. 22-W, 26 Nov. 1943;
Australia: ministry of Munitions, 1943. 2: Tropic Proofing Specifications
Committee No. 4, Organic Materials; 2nd meeting of InterService Committee No. 4,
13 Dec. 1943; Australian Scientific Liaison Bureau, Melbourne. 3: Tropic Proofing
Progress Report No. 2 for the period 29 Oct. to 31 Dec. 1943; Council for
Scientific and Industrial Research, National Standards Laboratory
Electrotechnology Section, Australia.)"
"Dr. B.J. Grieve was involved in research relating to fungal contamination of
field glasses in New Guinea. (W.A. Lonergan, personal communication, 21 June
1992)"
--page100. Howard, Richard. The Role of Botanists During World War II in the
Pacific Theatre. pp83-118. Macleod, Roy, ed. Science and the Pacific War:
science and survival in the Pacific 1939-1945. Dordrecht: Kluwer, 2000.
================================================== =========================
Notes on fungus from military, commercial, camera, & optical sources.
War Department Technical Manual TM 9-1580; Binoculars M3, M7, M8, M9, M13,
M13A1, M15, M15A1, M16, M17 and M17A1 and BC Telescope M65. 1953. (284p)
p246. To fungus proof the battery commander's telescope M65, fungicidal capsules
were sealed in the instrument. However, the active element not only kills fungus
but also speeds corrosion of metal and softens optical cements.
(Note: Antifungal capsules should be removed when they are found during
disassembly? This damage has not been reported by modern repairmen.)
----------
MIL-STD-810E Method 508.4 Fungus. Defines testing of optics' ability to
withstand fungus.
MIL-STD 810F Method 508.5 Fungus.
=========
Fungus Testing http://www.ntscorp.com/scripts/test/test320.html?tstcat=104
National Technical Systems fungus testing...To a greater or lesser degree, growing
fungus will use wood, paper, leather, hydrocarbons, PVC, polyurethanes, certain
plastics, certain paints and other materials as fuel. Live fungus can get under
protective covers and mar the appearance or degrade optical capabilities of your
product. Metabolic waste products from fungus cause corrosion.
The fungus test is an accelerated environmental test; therefore, the temperature
and moisture conditions are specified to support rapid growth of fungi and
accelerated deterioration of materials. NTS examines the following conditions.
--Do the materials support fungal growth
--How rapidly will fungus grow on the material
--How will the fungus affect the material, its mission and performance
--Is there a reversal process – can the fungus be removed?
Standard testing takes from 28 to 84 days....we are able to employ both US and
European fungus groups.
NTS works to all the standard specifications such as Telcordia; MIL-STD-202, 810;
ASTM D 120, D 470, D 518, D 1049, G21, 22, 29; Fed. Test Method Standard No. 191;
RTCA/DO-160 as well as D2020-92 (1999) Standard Test Methods for Mildew (Fungus)
Resistance of Paper and Paperboard as well as any custom fungus test you may
require.
=========
--Good quality lenses are assembled in 'clean rooms' where the air is micro-
filtered. Opening up a lens introduces more fungus spores
--Alcohols are ineffective compared to dilute solutions of ammonia (Windex).....a
50/50 mixture of hydrogen peroxide and household ammonia....(question of whether
it removes fungus, or if ammonia-peroxide mixture is in essence a good glass
cleaner, rather than a fungicide).....fungus killing formula among painters and
gardeners: Mix 1 gallon water with 1 pint Clorox and 2 oz. liquid
detergent........soak the parts in bleach or a commercial fungicide like
tilex.......vinegar, household strength or stronger acetic acid, is described as
effective in cleaning fungus if it is 'caught early'.
--real fungicides are hard to find and are all very toxic to humans. Ammonia or
bleach is only modestly effective, as anyone who has dealt with fungus growth in a
shower knows.
--Thymol crystals in a Dish, in an airtight Box, with the Item...Thymol is very
dangerous to Humans.....Leave for a few days, or a week.....Works well for Albums,
Prints, old negs and Slides..... Thymol Crystals from most scientific chemical
supply co.
--soaking the glass (not the metal!) in baths of a hydrogen peroxide-household
ammonia mixture, 50/50.
--high-intensity UV, a sunlamp, or even strong sunlight, these methods have mixed
success; modern lenses cemented with UV curing cements will absorb UV.
--negative ion generator (also known as ionizer) is the only sure fire way to
prevent mold
--alchohol to clean fungus off the glass.....the interior of the scope washed down
with a dilute solution of Chlorox (sodium hypochlorate) to kill all the mold
spores.
--periodically "gas" the components using formaldehyde gas. For example, remove
the optics, place in a zip-lock bag with some formalin (38%
formaldehyde)....formaldehyde may affect some components inside the lenses.
--enclose a teaspoon of paraformaldehyde powder in a small paper bag within the
microscope case....protects the microscope for a year or two and apparently has no
ill effect on lenses and the mechanical parts.
=====
Storage:
--a heated storage box....put several silica gel packets in the sealed
box....Drie-rite (CaSO4) can be corrosive.
--Parafilm wrapped around the lid of any old jar will keep indicator desiccant
blue for years.
--Tupperware brand is the best at sealing out humidity of all the commercial
sealable food storage containers.
--add N2 gas before sealing.
--do not store in leather or wood cases, which often promote fungus growth; store
in open air rather than any kind of case
--isolate lenses with fungus, don't store with uncontaminated glass.
Sources include: http://www.smu.edu/~rmonagha/bronfaults.html
http://www.smu.edu/~rmonagha/mf/fungus.html
================================================== =================
home page: http://home.europa.com/~telscope/binotele.htm
Many old optical instruments have fungus growth on a glass surface. Fungus
does not look like haze but has an appearance like hairs or tendrils branching
from a center. While the fungus can be removed by cleaning, it frequently has
etched the glass, since fungi secrete enzymes and acids to chemically alter their
environment so they can absorb nutrients. This etching requires repolishing,
which if done unprofessionally will ruin the instrument. It is not possible to
tell if the glass is etched until the fungus is cleaned. Maintenance of optical
instruments involves prevention of future fungus problems, especially if located
in damp regions.
To sum up the lengthy documentation below:
--WWII research programs on fungus in optical instruments (Turner, below) used
sodium ethylmercurithiosalicylate, now known as Thimerosal and widely used
consumer medical products. When mixed in paint used inside the binocular, this
was found effective at preventing fungus. It is not known if Thimerosal is so
used today.
--Hydrogen peroxide, or bleach, can be used to kill fungus.
--Leitz documents describe a fungus treatment of 94% distilled water, 4% clear
ammonia (for cleansing) and 2% hydrogen peroxide (to kill fungus).
--Carl Zeiss Oberkochen, dept. KuDi, sells: Fungus Cleaning Agent
"Fungusreiniger NEU". Dilute with ethyl alchohol, leave on glass for one hour or
more, then clean. Not poisonous but avoid contact with skin. 100ml bottle, INR
0117.362 500ml bottle, INR 0117.361 1000ml bottle, INR 0117.360
--Notes on treatment & prevention are found at the end of this text.
================================================== =======
1. Turner, J.S., et al. Tropic-Proofing of Optical Instruments by a Fungicide.
Nature 158 (Oct. 5, 1946) 469-473.
2. Trokojus, V.M. Chemistry of Sodium Ethylmercurithiosalicylate. Nature 158
(Oct. 5, 1946) 473-474.
3. Fay, J.W.J. Comments. Nature 158 (Oct. 5, 1946) 474.
4. Saxena, B.B.L., S.S. Nigam, & S.R. Sengupta. Fungal Attack of Optical
Instruments & Its Prevention. Indian Journal of Technology 1 (1963) 283-286.
5. Horne, Douglas. Optical Production Technology. Bristol: Adam Hilger, 1972.
pp.50-51. Growth of fungus on lenses.
6. Yoder, Paul. Opto-Mechanical Systems Design. N.Y.: Marcel Dekker, 1993. p.60-
62. Fungus
7. Howard, Richard. The Role of Botanists During World War II in the Pacific
Theatre. page 100. Macleod, Roy, ed. Science and the Pacific War: science and
survival in the Pacific 1939-1945. Dordrecht: Kluwer, 2000.
8. Notes on fungus from military, commercial, camera, & optical sources.
=================================================
Tropic-Proofing of Optical Instruments by a Fungicide.
J.S. Turner, E.I. McLennan, J.S. Rogers, & E. Matthaei. University of Melbourne.
Nature 158 (Oct. 5, 1946) 469-473.
It is remarkable that the problem of the deterioration of optical instruments
by fungi has remained so long without thorough investigation. Until 1939 very few
people seem to have realized that fungi can grow actively on or over the internal
optics of binoculars, cameras, etc., exposed to warm and humid conditions. The
trouble became acute, however, in Australia when military units went into action
in New Guinea.
Not only were the facilities for storage of instruments extremely primitive in
the early stages of this campaign (1), but, as has since been shown, parts Of New
Guinea are climatically the worst possible Places for fungal troubles. In a short
time, the fungal infection of instruments designed for temperate regions became a
major problem. Optical instrument workshops, adequately equipped and staffed for
normal repair work, found themselves entirely unable to cope with the flood of
fungus-infected instruments which descended upon them. Many types of instruments
lasted only for four to eight weeks before infection; and, very often, new
instruments awaiting issue in depots were found to be deteriorating rapidly on the
shelves because of fungal attack. In fact, instruments in store were affected more
often than those in use, and the trouble was greatest where they were housed in
leather cases and stored in wooden boxes.
Accordingly, in 1943, the Australian Scientific Instrument and Optical Panel
(an advisory panel to the Ordnance Production Directorate of the Ministry of
Munitions, Australia) set up a special subcommittee, which carried out research on
this problem and which has issued interim reports from October 29, 1943, up to the
present time. (2) Considerable research was carried out during the same period in
both the United States (3) and Great Britain. (4) In this report we shall
summarize the results of the Australian work, which led to a reasonably effective
method of tropic-proofing optical instruments.
The fungi which grow in optical instruments belong to the groups Phycomycetes,
Ascomycetes and Fungi Imperfecti. The following species were frequently isolated
from instruments which had been in New Guinea: Penicillium spinulosum, Thom.; P.
commune, Thom.; P. citrinum, Thom.; Aspergillus niger, Van Tiegh.; Trichoderma
viride, Pers. ex-Fr.; Mucor racemosus, Fres.; and M. ramannianus, A. Moeller. So
far, Monilia crassa has not been isolated from Australian instruments, although
Dr. W. G. Hutchinson (5) of the United States, found this to be a common species
in the Panama zone, and it has also been recorded as frequent in West Africa by
Major I. G. Campbell. (6)
The fungal spores germinate on the moist surface of the glass lenses or prisms
or, more frequently, on particles of dust, luting wax, cork and other organic
debris. The mycelium spreads thence over the whole surface of the clean optical
glass. The moulds are particularly troublesome when they grow on graticules, but
they are also capable of obscuring lenses and prisms. The fine hyphal threads in
contact with the glass surfaces are often surrounded by minute condensed water
droplets or by droplets of alkali-soluble substances liberated from the glass
itself. If the mycelium remains for many months in contact with the glass, it is
capable of etching a pattern into it. More commonly, when removed, the mycelium.
leaves only a slight stain resembling an oil film which can be removed by cerium
oxide polishing.
The committee concentrated at first on methods for civilian binoculars which
were to be issued to the Australian Services. It was early decided that it would
be futile to attempt to desiccate these instruments or to ensure that they were
optically clean and sterile when dispatched. A search was made, therefore, for a
suitable volatile fungicide which could be placed in the instrument during its
first reservicing and fitting with graticules. The requirements of the fungicide
were: (a) toxicity to all possible contaminants, (b) action at a distance (that
is, volatility) for the substance could not be placed directly on the optics, (c)
stability in moist air and to a temperature of at least 60 degrees C., (d)
persistence of action over some months or, preferably, years, (e) lack of power to
corrode metals, especially brass, steel, and aluminium alloys, (f) non-toxicity to
man, (g) mite repellent (because mites have been shown to enter optical
instruments carrying fungal spores with them), (h) availability in war-time.
As might be expected, very few of the known fungicides passed even the first of
these tests. The initial laboratory experiment was designed to select a fungicide
with the properties noted in (a) and (b) above. For this purpose the substance
under test was incorporated in luting wax and a drop of this was melted on to a
microscope slide. This was then inverted and a hanging-drop culture of mixed
spores from optical instruments was set up around the wax.
The following known fungicides were shown to be ineffective under these
conditions for some or all of the moulds concerned: 'Ceresan', 'Agrosan',
'Shirlan', 8-hydroxy-quinoline, penta-brom-phenol, tetramethyl thiuram disulphide,
tri-brom-phenol, azo-chloranide, clove oil, copper naphthenate, phenyl mercuric
acetate, tri-oxy-methylene, methyl alcohol and thymol. Many other fungicides were
not tested here, following adverse reports on their properties from other workers,
for example, naphthalene, paraformaldehyde. Thymol was the most promising, but
further experiments with it were discontinued when it was found that an organic
mercurial completely suppressed the germination of all the species with which we
were concerned. This substance was sodium ethylmercurithiosalicylate, referred to
here as 'M.T.S.'. It had been produced in Australia on a large laboratory scale
by Prof. V. M. Trikojus and his associates of the Universities of Sydney and later
of Melbourne. It was in use by the Australian Army Medical Corps for the
preservation of blood. Prof. Trikojus suggested its trial for tropic proofing, and
very, extensive tests have shown it to be the best fungicide so far investigated
by us for this particular purpose.
At first, the M.T.S. was incorporated only into luting waxes, but later it was
mixed with a black lacquer, which was used to cover the interior metal surfaces of
optical instruments. It was mixed with this paint to give a concentration of 0.2
per cent in the liquid and it was also incorporated in the microcrystalline wax
which we used for luting purposes. Our experiments show that the dry M.T.S., pure
or in paint, is scarcely volatile at all, but in the presence of water vapour it
is decomposed, probably by hydrolysis, to give a very active fungicidal and
fungistatic vapour.
Following hanging-drop tests, binoculars and rangefinders were painted
internally with the poisoned lacquer and mixed fungal spores were dusted on thin
agar films with which the optics had been coated. The instruments were then
assembled in the normal way and placed in a tropic-proofing test cabinet under
conditions of high humidities and temperatures. Some of the instruments were also
wrapped in damp calico which had been sprinkled with spores, and living mites were
introduced into the cabinets. Under these conditions, no fungal growth occurred
inside the treated instruments, but there was abundant growth in the control
instruments which had not been poisoned. In later experiments, cylindrical tins of
300 cubic cm. capacity were painted internally with black lacquer, some of which
had been poisoned with M.T.S. or with its butyl or methyl esters, in
concentrations of 0.2 per cent. The space inside was saturated with water vapour,
and each tin contained, for the actual test, a microscope slide covered with a
film of nutrient agar and dusted with fungal spores. In no instances have spores
germinated in tins containing the M.T.S. poisoned paint, although some of these
tests were carried out six months after the paint had been applied to tins open to
the atmosphere through minute holes. The vapour arising from the M.T.S. paint has
been shown to kill the spores as well as to inhibit their growth. Further
experiments, carried out by an officer of the Victorian Department of Agriculture,
have shown that the vapour arising from the hydrolysis of M.T.S. is lethal to
mites, but it does not act as a mite repellent. This corresponds with our own
experience ; and we have found that, while mites entering M.T.S. treated
instruments are killed, their bodies do not then act as centres for the growth of
fungi.
In the experiments with closed tins referred to above, some germination of
spores did take place when the paint contained either the butyl or the rnethyl
ester of M.T.S., but only when the tins had previously been stored for six months.
The methyl ester was the less promising, but Dr. Hutchinson, of the United States,
has informed us that the butyl ester which we supplied to him was rather more
effective than M.T.S. itself in his Panama Zone experiments. This ester has the
advantage of being soluble in lipoid solvents, and further trial may prove it to
be a fungicide of better value than the sodium salt (M.T.S.) itself.
Once the value of M.T.S. as a fungicide was established, it became necessary to
test its corrosive power. The first results were most discouraging, as it was
found that aqueous solutions of M.T.S., both in the acid form and as the sodium,
copper and zinc salts, brought about rapid accelerated corrosion of aluminium and
some slight corrosion of brass. The corrosion was of a type which suggested that
free mercury ions were released in solution and catalysed the reaction. However,
it has since been found that when incorporated in a suitable lacquer, the M.T.S.
causes no corrosion at all of the metal under the lacquer or of unpainted damp
metal surfaces near by, even when the test piece is enclosed in a small volume of
warm, damp air. On the contrary, the layer of lacquer protects the metal surfaces
against the action of water vapour, which is known to cause extensive corrosion in
optical instruments exposed to tropical conditions. So far as experiments have
gone, there is no evidence that M.T.S. attacks lens cements (balsam or n-butyl
methacrylate), nor does it cause the filming of optics.
This lack of corrosion by M.T.S. in paint may have been due in part to the
special properties of the paint we employed. We have recommended the use of a
nitro-cellulose lacquer which dries quickly to a reasonably matt surface. It is
manufactured by B.A.L.M. under the name of 'Duco Enamel Lacquer'. Recent reports
from England indicate that other lacquers are not necessarily suitable. We have
also found it not advisable, from the point of view of corrosion, to incorporate
the M.T.S. into the zinc oxide-retinax grease used as a lubricant for eyepiece
threads. It should be noted here that the M.T.S. makes up 0.2 per cent of the
liquid lacquer; when this dries put, the mercurial poison is dispersed in the film
at a concentration approaching 0.8 per cent.
Our corrosion tests are supplemented by observations on binoculars which have
been tropic-proofed with M.T.S. and exposed for long periods as follows: 1- some
instruments were kept for three months in the laboratory in Melbourne; 2- others
were exposed for two months in a test chamber to 100 per cent relative humidity
and 30 degrees C.; 3- about thirty instruments were exposed to tropical conditions
in New Guinea for two and a half months and then returned to Melbourne for
examination.
Corrosion in all these instruments was limited to that taking place on exposed
aluminium alloy surfaces and its extent was that which would be expected, from
control experiments, to occur whether M.T.S. was present or not. Experiments at
the Munitions Supply Laboratories, Maribyrnong, have also shown that black lacquer
containing 0.2 per cent M.T.S. does not cause 'season cracking' of brass. Finally,
although many thousands of optical instruments have now been tropic-proofed in the
way recommended, there has been no report from the Services of corrosion in these
instruments.
These tests and observations have convinced us that there is very little danger
of corrosion by M.T.S. in paint. They have, at the same time, led us to recommend
that all internal metallic surfaces of optical instruments for tropic use should
be painted or anodized so as to render corrosion by water vapour negligible.
Since 1943, numerous field experiments in New Guinea have confirmed the value
of M.T.S. as a fungicide in optical munitions. A short test in 1944 with thirty-
four binoculars in stores at Milne Bay, Lae and Port Moresby was inconclusive in
that many of the control instruments did not become infected. However, at Lae,
four binoculars containing M.T.S. remained free from infection on all optics,
while two untreated instruments were all infected on various optical surfaces.
Later, twenty binoculars and six rangefinders were exposed in Kunai grass near
the jungle for six months and then returned to Melbourne for examination. One side
of each of the binoculars was tropic-treated, while the other side acted as
control. Three rangefinders were treated and three acted as control. After six
months, there was no infection in any of the treated sides of the binoculars,
except for one slight trace of non-sporing fungus on one prism. Practically all
the untreated sides were infected, some badly. All three treated range-finders
were free of fungus, while all the untreated instruments were badly infected. This
is a striking proof of the efficacy of M.T.S., as the rangefinders are badly
sealed instruments and yet even in these the fungicide retained its activity.
A long-term experiment has just been started in New Britain. One hundred
instruments (binoculars) have been assembled with exactly the same luting, lacquer
and eyepiece grease; but on one side of each instrument the lacquer and luting
contain M.T.S., while the other side is free of this substance. Twenty-five pairs
are to be returned to Melbourne at six-month intervals for examination. The
efficacy of the fungicide will thus be tested over a period if two years.
Three pairs of binoculars treated with M.T.S. in Melbourne have been exposed to
tropical conditions in the Panama zone. They are still under test, but they have
so far remained free of fungus for a period of five months.
Perhaps the most striking evidence in favour of M.T.S. is its control of fungal
infection in aircraft cameras, which are, of course, badly sealed instruments. At
the beginning of 1944, the secretary of the Scientific Instrument and Optical
Panel was approached by an officer of a camera repair unit of the U.S.A.A.F., who
reported very severe damage to aircraft cameras caused by fungi.. The unit adopted
the M.T.S. treatment for all its cameras and has reported that none of the 350
cameras so treated became infected during a period when approximately a hundred
lenses, including fifty from aircraft cameras, were returned for the removal of
fungi from the optics. One aircraft camera, treated with M.T.S., has remained
internally free of fungus for a period of twelve months, although, on occasion,
fungi have had to be wiped off the external lens faces. Officers of this unit have
also found that the growth of fungus in fibre cases for carrying cameras could be
prevented by coating the cases internally with black lacquer containing M.T.S.
The Australian Military Forces adopted the M.T.S. treatment in 1944, and all
types of optical instruments manufactured or assembled in Australia, including
thousands of binoculars, have been treated in this way. The R.A.A.F. and one
section of the U.S.A.A.F have also adopted the method, as has the Royal Australian
Navy. Recent reports from Britain indicate that the method is undergoing tests by
the R.A.F., although it is there recommended that internal metal surfaces should
be anodized or covered with a primer before the poison lacquer is applied.
In aqueous solution M.T.S. will prevent the growth of Penicillium at
concentrations so low as 1 in 2millions. It is used locally in 1 in 1,000
solution, as a tincture for skin disinfection and as a nasal spray, and it has
also proved of value for preserving blood serum. (7) It is regarded as most
unlikely to cause any harm to man in the concentrations recommended for tropic
proofing, as the lethal dose for man is believed to be about 1,000 milligrams. Its
action at a distance is best shown as follows. Black paint containing 0.2 per
cent M.T.S. is used to coat glass plates approximately 4 in. square; the painted
surface is then apposed to a similar plate coated with thin agar dusted richly
with Penicillium spores. The two plates are kept 2 mm. apart by spacing strips
round the edges. No spores germinate (in fact they are killed) on the agar when
the two plates are incubated under humid conditions. If, however, the paint is
applied in two narrow bands forming a cross, spores do germinate to form a thin
mycelium, but only in the corners of the plate. The mycelium then slowly spreads
towards the middle where the concentration of toxic vapour is at the maximum.
Under these conditions it appears that mutual reaction between the fungus and the
vapour keeps the concentration down and allows slowly continued growth of
mycelium. The vapour (which presumably contains a mercury compound) takes effect
whether the paint lies above or below the agar; but in some experiments it was
noticed that the inhibition of growth on plates held vertical was exerted over a
greater distance on the lower sides of horizontal painted bands.
Incorporated into paints, M.T.S. may prove to be a useful fungicide apart from
its application to optical munitions. For example, Mr. P. G. Law has suggested its
use as a preventive of mould spotting in framed prints. Preliminary tests indicate
that, if the wooden back of a picture frame is painted with M.T.S. lacquer on the
side facing the print, mould growth in humid atmospheres is prevented. Technical
officers in museums and galleries may find that further investigation along these
lines is worth while.
The authors desire to acknowledge the valuable assistance of the other members
of the Scientific Instrument and Optical Panel committee: Mr. P. G. Law, Mr. J. W.
Blamey, of the University of Melbourne; Mr. G. C. Wade, of the Victorian
Department of Agriculture. Our thanks are also due to Prof. V.M. Trikojus, Mr.
G.M. Willis of the Metallurgical Department, University of Melbourne, Mr. M. Pack
of B.A.L.M. and several officers of the Munitions Supply Laboratories, who all
made contributions towards the solution of the problem. The Tropical Scientific
Section of the Scientific Liaison Bureau, Melbourne, rendered assistance in the
carrying out of the field tests in -New Guinea.
Footnotes.
1. Scientific Liaison Bureau, Australia. "Report on the condition of Service
Material under tropical conditions in New Guinea." Restricted. October 21, 1943.
2. Scientific Instrument and Optical Panel, Ministry of Munitions, Australia.
"The Tropic Proofing of Optical Instruments, Part I", July 1944.
3. O.S.R.D. Reports, U.S.A., No. 1833, July 1943. No. 4188, September 1944.
4. Reports of Optical Instruments Panel of Conference on Tropic Proofing,
Controller of Chemical Research and Development, Ministry of Supply, Great
Britain, papers issued under MG/OPT.
5. Hutchinson, W. G., in O.S.R.D. Report No. 1833, July 1943.
6. Campbell, Major I. G., "Fungi in Optical Instruments under Tropical
Conditions, and Possible Control", D.M.E. War Office, Great Britain, December
1944.
7. Simmons, R. T., and Woods, E. F., Austr. J. Sci. 8 (1946) 108.
--------------------------------------
Chemistry of Sodium Ethylmercurithiosalicylate.
Prof. V.M. Trokojus, University of Melbourne.
Nature 158 (Oct. 5, 1946) 473-474.
Sodium thylmercurithiosalicylate is a white crystalline solid, melting at about
230 degrees C. and easily soluble in water and the lower alcohols, but insoluble
in lipoid solvents. Its preparation -was first reported by Kharasch in 1928 (8)
(cf. also Waldo (9)).
In the manufacture of the drug in Australia for plasma preservation and tropic-
proofing, undertaken initially by J. E. Falk and since, in larger quantities, by
R. H. Hackman, ethylmercuribromide was condensed with thiosalicylic acid (15 per
cent excess) in aqueous-ethanol with the equivalent of 2-5 mol. sodium hydroxide.
About a kilogram of thiosalicylic acid was used per batch. The crude
ethylmercurithiosalicylic acid (by precipitation with hydrochloric acid) was
purified by recrystallizing <section cut>
Both compounds are insoluble in water but readily soluble in lipoid solvents,
an obvious advantage when applying the materials to paints and lacquers; moreover,
the methyl ester can be obtained in a pure condition much more conveniently than
the sodium salt.
The action mechanism of the sodium salt as a fungistatic and fungicidal agent
is uncertain. It has been proved to act at a distance, but it is improbable that
a sodium salt of this configuration would possess a significant vapour pressure.
Kharasch has pointed out that aqueous solutions of the sodium salt tend to break
down to ethylmercurihydroxide (III) and sodium thiosalicylate, the latter, in the
presence of oxygen, passing irreversibly to the dithiosalicylate (IV). Thus the
access of water vapour, providing conditions for fungal growth, might also favour
a similar breakdown of the lacquer-incorporated mercurial, or even further to more
volatile substances.
Footnotes.
8. Kharasch, M.S. U.S.P. 1 (1928) 672, 615.
9. Waldo. Journal Amer. Chem. Soc. 53 (1931) 993.
---------------------------
Comments by Dr. J.W.J. Fay, Ministry of Supply.
Nature 158 (Oct. 5, 1946) 474.
I am glad to have seen these two interesting papers, and take the opportunity
of offering the following comments on British experience.
Two factors have militated against the use in Britain of M.T.S. on other than
an experimental scale.
First, in the design of new instruments, or the modification of old types, the
tendency has throughout been towards the improvement of sealing and of packaging.
This, coupled with the use, if necessary, of a desiccating agent, is considered
the ideal at which to aim, since the need of a fungicide is eliminated.
Secondly, in connexion with the protection of old instruments, including ex-
civilian surrendered types of unknown history, the incorporation of volatile
fungicides was not without its dangers. Thus, various substances tried gave rise
to such troubles as softening of cements, corrosion and filming. Nevertheless, the
need for a suitable fungicide was recognized and many were tested.
Among these, M.T.S., of which the vapour pressure is extremely low, was found
to depend for its action upon a decomposition in the presence of moisture, giving
rise to a volatile mercury compound which is presumably the active agent. The
decomposition was found to be accompanied by a corrosion danger, and in the
lacquers we have used this danger has not yet been overcome. We are, however, now
awaiting samples of Australian lacquer for test.
In general, therefore, even in the case of old-type instruments, our attitude
has been to improve sealing and methods of servicing, packing and storing, and the
tendency is in any case to regard the incorporation of a desiccant as preferable
to the use of fungicides.
With reference to the New Guinea experiments, we have had the opportunity of
examining a few of the instruments tested, and our view is that while the results
afford evidence of the superiority of the new complete Australian 'tropical
treated' method over the old one, it is not entirely clear, in the absence of true
controls, how much of the improvement is to be ascribed to the use of M.T.S. For
this reason, we shall look forward with great interest to the results of the long-
term New Britain experiments in which rigid controls are apparently included.
================================================== =======================
Saxena, B.B.L., S.S. Nigam, & S.R. Sengupta. Defence Research Laboratory
(Stores), Kanpur.
Fungal Attack of Optical Instruments & Its Prevention.
Paper presented at the Symposium on Instruments, held at TDE (Instruments), Dehra
Dun, in November 1959.
Indian Journal of Technology 1 (1963) 283-286.
The nature and pattern of fungus infestation on various components of
binoculars in hot, humid conditions (Calcutta, Cochin and Bombay) have been
investigated. The organisms isolated and identified include: Aspergillus niger, A.
fumigatus, A. candidus, Penicillium sp., Paecilomyces sp., Syncephalastrum sp.,
Sepedonium sp., Curvularia sp., Fusarium sp., Monilia sp. and Cladosporium sp.
Prisms and OG lenses show greater fungal infestation than FL or EL lenses;
graticules and lutings show slight to moderate degree of incidence. Protective
treatments tried on brass and aluminium materials indicate that satisfactory
protection is provided by: 1- incorporating fungicides like Cresatin, Merthiosol,
copper naphthenate and pentachlorophenol in lacquers, varnishes, lutings, waxes,
greases and paints applied to various components of the instrument; or 2-
depositing on the surface, coating compositions containing suitable fungicides by
chemical or electrolytic methods.
In tropical climate characterized by high temperature and humidity accompanied
by nocturnal condensation, optical instruments are prone to fungal attack during
storage. Instruments such as binoculars, rangefinders, telescopes, cameras and
similar other equipment lose their functional efficiency when they are attacked by
fungi and thus cause considerable financial loss. Although as early as 1932, the
fouling of binoculars by fungi was recorded in India (1), it was not until 1939
that it was realized that fungi can grow actively on glasses, prisms of binoculars
and on lenses of cameras. (2) In 1943, it was reported from New Guinea that the
presence of fungal colonies in optical equipment was the 'rule rather than the
exception'. (3) Under favourable conditions, fungal infestation is not confined
to a specific component of an optical instrument but spreads to all the parts.
Optical glasses, prisms, lutings, seals, greases, waxes, lacquers and varnish
coatings are all attacked, pointing to the need for an overall improvement in
materials used in the fabrication of optical instruments.
Workers in India were among the first to identify the actual nature of the
microorganisms responsible for the unserviceability of optical instruments. In
1940, at Rawalpindi arsenal the use of desiccating valves fitted to binoculars as
a means of reducing the fouling was resorted to. Work was simultaneously carried
out in the USA, the UK, Canada and Australia to study the nature of deterioration
of optical instruments and also to study the behaviour of a large number of tropic
proofing compounds. In 1943, Hutchinson (4) examined a large number of optical
instruments and recommended the use of 'Cresatin' (m-cresol acetate). In 1944,
Campbell carried out large-scale investigations (5) in order to develop antifungal
as well as antifilming measures for use in the Service equipment under jungle
conditions of storage and usage. In the same year similar type of work was done in
Australia. In India, at the then Inspectorate of Scientific Stores (Instruments
and Electronics), Calcutta, work was carried out on the problem of fogging,
filming and fungal infestation of optical instruments. In collaboration with that
organization, Defence Research Laboratory (Stores), Kanpur (then known as Ordnance
Laboratories), investigated the nature and extent of microbial damage in
binoculars. In 1945, the Directorate of Armaments (India) carried out extensive
exposure trials at Calcutta and later in 1948 at Cochin and Colaba (Bombay). These
trials were on different types of optical instruments and consisted in subjecting
them to adverse storage conditions.
Failure of Optical Instruments
The failure of optical instruments in the tropical regions may be due to
fogging, filming or fungus infestation. In addition, corrosion of metallic parts
of binoculars has also been noted. Fogging involves the occurrence of moisture
droplets on glass surface due to condensation of moisture from the atmosphere. It
is transient and depends solely on the atmospheric humidity of the place. Filming
involves the production of a greyish coating on the optical surface and it is
progressive and not transient. When condensation / fogging occurs on the optical
surfaces, free alkali which is present on the surface of the glass goes into
solution. This alkaline solution reacts with the carbon dioxide of the air and
forms a solution of alkali carbonate. When the instrument gets dry, the solution
evaporates and leaves carbonate crystals on the glass surface. Thus, a permanent
film is left on the glass surface. Filming is also caused by the condensation of
volatile constituents of eyepiece lubricants and sealing materials. Among the
optical instruments, binoculars are most prone to the development of moulds. In
other instruments, too, the liability to mould growth is favoured by openness of
construction, i.e. whether or not the instrument has focussing eyepieces or
bodies, adjustment and apertures or 'breaks' due to rotating mechanism. Even
sealing compounds aid in the development of moulds.
The fungal spores germinate on the moist surface of the glass lenses or prisms
or more frequently on particles of dust, luting, wax, cork and any organic debris.
The mycelium spreads thence over the whole surface of optical glass. The fungi are
particularly troublesome when they grow on the graticules. They are also capable
of obscuring lenses and prisms. Fungi grow well on the outside of the object
glasses and more so when the instruments are stored in mouldy cases. By far the
most important source of fungi found within optical instruments or on the exterior
is the mouldy case of the instrument.
The present communication presents the results of a preliminary study on the
isolation and identification of fungi from a few typical affected pieces of
binoculars. The use of certain protective agents has also been investigated.
Experimental Procedure
The binoculars received from the Inspectorate of Scientific Stores, Calcutta,
and from the Technical Development Establishment (I & E), Dehra Dun, after
exposure trials at Cochin and Colaba, were examined for the nature and pattern of
fungal attack on the various components. Cultural studies of the fungal growth on
glasses, prisms and graticules were also made.
Visual and microscopic examination: Fungal infection was observed in varying
degrees on different parts of the binoculars. The lenses and prisms were most
affected, followed by graticules, lutings and greases. Even the paint was attacked
by fungi. In some cases the fungus growth had etched the glass. Wherever dead
mites, debris or grit were found, fungal growth was luxuriant. The mycelium
branched profusely, often forming a dense compact mass bearing spores (Fig. 1).
When the food material was not in abundance, the growth on most of the prisms was
restricted to a very few delicate branched hyphae bearing occasionally few spores.
In extreme cases, where the growth was exclusively at the expense of the food
material present in the spore, the mycelium consisted of a few rudimentary hyphae
radiating from the spore in the form of a star (Fig. 2). When the growth of a
fungus started from the central region of the flat surface as in OG lens, it was
usually symmetrical in all directions (Fig. 3); and when the amount of food
material was abundant the growth was dense and spread out irrespective of the
species (Fig. 4).
In some cases, as a result of fungal action, luting and organic debris
partially dissolved in the condensed water vapour and spread out along hyphae
producing irregular opaque configuration, thereby interfering with light
transmissions (Fig. 5). In prisms, the growth started from the apex and radiated
on the two surfaces forming irregular ramifications. In some cases, the hyphae
branched profusely and were often enveloped with droplets of water throughout
their length, thereby causing fogging of the instrument (Fig. 6).
The patterns of fungal infection of lenses and prisms of binoculars can be
considered to belong to the following types: 1- A spidery fungal growth radiating
from a central point. The fungal growth is easily removable and does not etch the
glass surface. Chlamydospores are often found and conidiophores when produced may
bear only a few chains of spores. 2- 'Starfish' type, in which the growth is
flat, adhering closely to the glass like a thick whitish drop and on removal
leaves the colour on the glass. The growth is composed of fragmented hyphae
surrounded by droplets of water. 3- Minute circular spots which always etch the
glass. They consist of tiny fungal colonies on small particles.
Isolation of fungi: The following methods were adopted for the isolation of
fungi from the infected components of the binoculars: 1- The prisms were placed
in Petri dishes containing potato-dextrose agar (PDA) medium. After incubation for
a week at 30 degrees, plus or minus 2 degrees C, subculturing was done of the
fungi which were found growing. 2- A scraping of lacquer / varnish from the
inside of the binocular was obtained and the scraping was planted on PDA medium.
3- Tube culturing was done by placing a drop of sugar solution on the lens over
the fungus to be examined, and transferring with a platinum loop, after gentle
rubbing, to the surface of a PDA slant. These slants were incubated at 30 degrees,
plus or minus 2 degrees C, for a week and the organisms isolated. 4- Infected
lenses and prisms of binoculars were washed with sterile distilled water under
aseptic conditions and the surface growth was removed with small pieces of sterile
filter paper. These pieces were then plated out in Petri dishes with a small
quantity of water on Waksman medium. These Petri dishes were incubated at 30
degrees plus or minus 2 degrees C. for a week and the organisms isolated.
Nature, incidence and frequency of fungi: The fungi growing on optical
instruments belong to Phycomycetes, Ascomycetes and Fungi Imperfecti (2). Most of
the isolates from the binoculars were identified as common fungi. Similar types
have also been reported from Australia (2). The common types isolated belong to
Aspergillus and Penicillium groups. In some cases, due to prolonged desiccation
and unfavourable conditions hyphae and spores (observed under microscope) failed
to grow on the medium. The following fungi were isolated from the various
components of the binoculars: Aspergillus niger, A. fumigatus, A. candidus,
Penicillium sp., Paecilomyces sp., Syncephalastrum sp., Sepedonium sp., Cuvulvaria
sp., Fusarium sp., Monilia sp. and Cladosporium sp.
Along with fungi, bacteria and a few yeast cells were observed. Some of the
bacteria were chromogenic. Prisms and OG lenses showed greater fungal infection
than FL or EL lenses. Graticules and luting showed slight to moderate degree of
incidence.
Protective Treatments
Since moisture is the chief cause of fogging, filming and fungus growth, it is
imperative to prevent ingress of moisture into the instruments. Several methods of
controlling fungus fouling of optical surfaces have been reported, such as
sanitation (6), dehumidification (1), use of antidimming substances (unpublished
data from Defence Research Laboratory (Stores), Kanpur), and fungicides.
As part of the present study, the suitability and efficiency of several
fungicides when incorporated in lacquers, varnishes, luting, waxes, greases and
paints against fungal attack were investigated. The application of coatings (by
chemical / electrolytic methods) for the protection of metal against corrosion and
fungal attack was also investigated.
Lacquers: Nitrocellulose lacquer, cashew nut shell lacquer (CNSL), and BALM
Duco lacquer containing Cresatin (0.5 per cent), Merthiosol (0.34 per cent),
copper naphthenate (3.0 per cent) and pentachlorophenol (PCP) (1.0 per cent) as
fungicides were tested. It was found that: 1- CNSL is less susceptible than
nitrocellulose lacquer, 2- lacquers containing Cresatin, Merthiosol and PCP (1.0
per cent) are ineffective, and 3- matt-pigmented CNS lacquer with 2 and 3 per cent
PCP is effective. BALM Duco lacquer is also slightly susceptible to mould attack.
Varnishes: Matt-pigmented oil varnish black DTD 34, air-dried or stoved at 120
degrees C. for 4 hours and containing PCP Merthiosol and castor oil distillate,
were tested. It was found that: 1- stove-drying does not give satisfactory
results, and 2- matt-pigmented oil varnish (air-dried) with PCP (3-0 per cent) is
effective. Other treatments were unsatisfactory.
Luting, waxes and greases: Incorporation of PCP (1.0 per cent) in these
materials conferred resistance to mould attack.
Paints: Silicone paint aluminium (air-dried) and silicone paint yellow type
(stoved) were found to be susceptible to mildew attack.
Protective coatings: Experiments were carried out to find out suitable methods
by which protective coatings can be obtained by chemical or electrolytic action on
brass and aluminium. For brass, two methods were adopted successfully. In the
first method, the blackening was carried out by immersion of polished brass in a
cuprammonium bath containing copper carbonate and ammonium chloride and treated
with 0.2 per cent PCP, while the second method involved anodic oxidation of brass
in a caustic soda bath and treatment with 0.2 per cent PCP. In the case of
aluminium, the blackening was carried out by anodizing the aluminium and then
dyeing it with organic black dyes / black inorganic pigment. The panels were
treated with 0.2 and 0.4 per cent PCP.
The blackened brass and aluminium pieces were subjected to fungal growth test.
The results indicated that the above protective coatings are effective against
fungal growth. Matt finish is also adequately protective as compared to that
produced by BALM Duco lacquer containing Merthiosol.
Confirmatory trials based on the above findings were made with aluminium tubes.
The tubes were anodized, dyed and then treated with PCP in the same bath. The dye
concentration was 1.0 per cent and that of PCP 0.2 or 0.5 per cent. These were
also found resistant to fungal attack. These results indicate that the application
of a protective coating with a fungicide can provide satisfactory protection
against fungal attack. In the absence of indigenous production of synthetic
resins, coating with the fungicides by chemical or electrolytic methods seems to
be the best solution of the problem. Another advantage of coating the surface in
this manner would be that by eliminating solvents, the residual solvent effect in
producing fogging is overcome.
Acknowledgement
Grateful acknowledgement is made to the Paints and Physical Chemistry Groups of
this laboratory for the supply of different paints, varnishes and lacquers as well
as anodized metal components for microbiological assay. The authors are indebted
to Shri S.K. Ranganathan, Ex-Control Officer, Biological Branch of this
laboratory, for help and guidance in the preparation of this paper.
References
1. Rao, C.S., Tropic Proofing trials on optical instruments. (TDE, Instruments &
Electronics, Dehra Dun), 1947-48.
2. Turner, J.S., et al. Nature, Lond., 158 (1946), 469.
3. Magee, C.J. et al. Report on the condition of service material under tropic
condition in New Guinea (Scientific Liaison Bureau, Australia), 1943.
4. NDRC Communication No. SR/7/43/9032, 27 July 1943.
5. Campbell, I.G. Report on the development of fungus fogging and filming in
optical instruments under tropical condition, and possible control (Director of
Mechanical Engineering War Office, Great Britain), 1944.
6. OSRD Rep. No. 4118 (University of Pennsylvania, 1944.
================================================== =====================
Horne, Douglas. Optical Production Technology. Bristol: Adam Hilger, 1972. pp.50-51.
2.23 Growth of fungus on lenses.
Fungal growth on optical components in the tropics has been a problem for many
years, and there is no evidence that any of the thin film coatings are a deterrent
to the mycelia attacking the glass. Attempts to clean glass surfaces after they
have been contaminated by mould will fail, as the glass itself will have been
damaged, and prevention of the mould growth is the only effective cure to the
problem. The damage to the glass surface usually takes the form of a general
'greyness' so that the light passing through is diffusely scattered. This leads to
a reduction of contrast and 'veiling glare' and if the surface lies on a graticule
in the focal plane of an eyepiece system the damage becomes very noticeable.
Even if the air inside instruments is desiccated immediately after initial
cleaning and assembly, and then sealed in a suitable package, deterioration often
occurs. The main causes of deterioration, in addition to fungus growth, are
attacks by water vapour and from the vapours of lubricants and optical cements
used in the instrument.
Under tropical conditions once a certain level of internal humidity has been
reached the daily range of ambient temperature may cause alternate condensation
and evaporation of water on the surface of the glass. The material dissolved out
of the surface is precipitated during evaporation and forms an alkaline solution
on the following condensation which further hastens the attack.
Where volatile machining fluids have been used during manufacture 'filming' may
occur unless the instrument parts have been very carefully cleaned before
assembly, and subsequently desiccated in a vacuum.
The natural grease of the hands may be found in polishing cloths which have not
been chemically cleaned and can cause 'films' to form on glass surfaces.
Certain types of brass which are often used in graticule or lens mounts may
contain free lead, which is readily soluble in water, and can creep or diffuse
from adjacent metal surfaces on to the surface of the glass and cause
deterioration under variable temperature conditions.
Most fungal damage arises during storage, and silica-gel bags will reduce the
ambient humidity and so make attack less likely. Sealing of the optical parts is
usually impossible owing to the need to maintain relative movements of parts for
focusing or rotation, as in theodolites or other surveying instruments.
If photographic lenses can be sealed, a clear metal lacquer containing 5%
salicylanalide (based on non-volatile content) can be used as a fungicide sealant.
The general approach is to introduce a fungicide which is relatively non-
volatile but still adequately lethal. Phenylmercuric acetate and Merthiosal (MTS)
are used with some success. All fungicides at present in use:
(a) Are toxic to humans.
(b) Cause condensation on glass surfaces.
(c) Have a deleterious effect on optical cements.
(d) Tend to produce dermatitis.
(e) Corrode metal parts, particularly aluminium alloys.
=================================================
Yoder, Paul. Opto-Mechanical Systems Design. N.Y.: Marcel Dekker, 1993.
p.60-62. Fungus
When glass components in optical instruments such as telescopes, binoculars,
cameras, and microscopes are exposed for long periods to warmth and high humidity,
films and localized deposits of mold may develop. Particularly troublesome in
tropical climates, these organic contaminants degrade performance by introducing
scatter at early stages of development (Rodionova et al., 1972); later they may
permanently damage optical surfaces by etching patterns into the material.
Baker (1969) provided a bibliography of 51 articles and papers published between
1941 and 1969 on the general subject of "tropic proofing" optical instruments.
Mold fungi have been found to germinate and grow on glass surfaces even though the
surfaces had been thoroughly cleaned to remove fingerprints, dust particles, and
lubricants (Theden and Kerner-Gang, 1965). The microscopic spores are ubiquitous
and seem to be able to supply sufficient nutrients internally to support limited
growth. Some glasses with high resistance to climate and acid seem to resist
fungus as well. Others (such as KzFS4) seem to impede mold growth, at least at
high humidity levels, although they are otherwise susceptible to climatic and acid
conditions. This contradictory behavior indicates that the chemical composition of
the glass plays a role in mold susceptibility.
Sprouse and Lawson (1974) reported evidence from tests conducted in the tropics
(Panama Canal region) to the effect that natural organic compounds condensed on
surfaces of glass and steel could serve as nutrient sources for fungal growth. It
was thought that, in the tropics, organic compounds (hydrocarbons) could come from
vegetation effluents. Monoterpenes (empirical formula C10 H16) previously thought
to play a role in tropical fungal accumulation were not found in any significant
quantity in the tropical atmosphere sampled. An aliphatic ester common to certain
tropical grasses was found to be present in significant quantity in that
atmosphere.
Baker (1967) evaluated some fungicides as mold preventive agents on optics. Later,
he described possible adverse effects of two fungicides (Baker, 1968). Baigozhin
et al. (1977) reported experiments with some chemically unstable optical glasses
that had been protected by fungicidal coatings that did not alter the glasses
optical properties. Optics protected with silicone films containing arsenic,
mercury, or tin resisted fungus tests for 3 to 4 months, whereas unprotected
optics of the same glasses were overgrown with fungus within 1 month of the same
test.
Harris and Towch (1989) described a series of environmental tests conducted on
several types of infrared windows intended for use in FLIR systems. They included
mold growth in this program, expecting to find the materials to be impervious to
this damage hazard. After 28 days, the test results indicated that a zinc sulfide
sample had lost most of its rain-resistant coating while a monocrystalline
germanium window showed coating damage. Transmission losses for these samples
exceeded what would be expected if the coatings were completely removed. Similar
control samples did not incur any damage or transmission loss so the degradation
was attributed to the effects of mold.
Baker, P.W. An Evaluation of Some fungicides for Optical Instruments. Int.
Biodeterioration Bull. 3:59, 1967.
Baker, P.W. Bibliography on Tropic Proofing of Optical Instruments. Royal Radar
Establishment Tech. Note 747. Malvern, England. 1969.
Theden, G. & W. Kerner-Gang. Results of Investigations on the Contamination of
Optical Glass by Fungi. (Glastec. Ber. 37:200, 1964). Translation, U.S. Defense
Documentation Ctr., Document AD458907, 1965.
================================================== ======================
"In Canada, mycologists of the Division of Botany of Agriculture developed
'Tropic proofing for war equipment', especially methods of preventing etching of
the optics of binoculars and riflescopes. (D.B.O. Saville ex W.L. Minshall,
personal communication, 16 July 1992)"
"In Australia, several organizations paid attention to problems of tropical
deterioration affecting optical equipment. (1: Report on Tropic Proofing of
Optical Instruments. Optical Munitions Panel Paper No. 22-W, 26 Nov. 1943;
Australia: ministry of Munitions, 1943. 2: Tropic Proofing Specifications
Committee No. 4, Organic Materials; 2nd meeting of InterService Committee No. 4,
13 Dec. 1943; Australian Scientific Liaison Bureau, Melbourne. 3: Tropic Proofing
Progress Report No. 2 for the period 29 Oct. to 31 Dec. 1943; Council for
Scientific and Industrial Research, National Standards Laboratory
Electrotechnology Section, Australia.)"
"Dr. B.J. Grieve was involved in research relating to fungal contamination of
field glasses in New Guinea. (W.A. Lonergan, personal communication, 21 June
1992)"
--page100. Howard, Richard. The Role of Botanists During World War II in the
Pacific Theatre. pp83-118. Macleod, Roy, ed. Science and the Pacific War:
science and survival in the Pacific 1939-1945. Dordrecht: Kluwer, 2000.
================================================== =========================
Notes on fungus from military, commercial, camera, & optical sources.
War Department Technical Manual TM 9-1580; Binoculars M3, M7, M8, M9, M13,
M13A1, M15, M15A1, M16, M17 and M17A1 and BC Telescope M65. 1953. (284p)
p246. To fungus proof the battery commander's telescope M65, fungicidal capsules
were sealed in the instrument. However, the active element not only kills fungus
but also speeds corrosion of metal and softens optical cements.
(Note: Antifungal capsules should be removed when they are found during
disassembly? This damage has not been reported by modern repairmen.)
----------
MIL-STD-810E Method 508.4 Fungus. Defines testing of optics' ability to
withstand fungus.
MIL-STD 810F Method 508.5 Fungus.
=========
Fungus Testing http://www.ntscorp.com/scripts/test/test320.html?tstcat=104
National Technical Systems fungus testing...To a greater or lesser degree, growing
fungus will use wood, paper, leather, hydrocarbons, PVC, polyurethanes, certain
plastics, certain paints and other materials as fuel. Live fungus can get under
protective covers and mar the appearance or degrade optical capabilities of your
product. Metabolic waste products from fungus cause corrosion.
The fungus test is an accelerated environmental test; therefore, the temperature
and moisture conditions are specified to support rapid growth of fungi and
accelerated deterioration of materials. NTS examines the following conditions.
--Do the materials support fungal growth
--How rapidly will fungus grow on the material
--How will the fungus affect the material, its mission and performance
--Is there a reversal process – can the fungus be removed?
Standard testing takes from 28 to 84 days....we are able to employ both US and
European fungus groups.
NTS works to all the standard specifications such as Telcordia; MIL-STD-202, 810;
ASTM D 120, D 470, D 518, D 1049, G21, 22, 29; Fed. Test Method Standard No. 191;
RTCA/DO-160 as well as D2020-92 (1999) Standard Test Methods for Mildew (Fungus)
Resistance of Paper and Paperboard as well as any custom fungus test you may
require.
=========
--Good quality lenses are assembled in 'clean rooms' where the air is micro-
filtered. Opening up a lens introduces more fungus spores
--Alcohols are ineffective compared to dilute solutions of ammonia (Windex).....a
50/50 mixture of hydrogen peroxide and household ammonia....(question of whether
it removes fungus, or if ammonia-peroxide mixture is in essence a good glass
cleaner, rather than a fungicide).....fungus killing formula among painters and
gardeners: Mix 1 gallon water with 1 pint Clorox and 2 oz. liquid
detergent........soak the parts in bleach or a commercial fungicide like
tilex.......vinegar, household strength or stronger acetic acid, is described as
effective in cleaning fungus if it is 'caught early'.
--real fungicides are hard to find and are all very toxic to humans. Ammonia or
bleach is only modestly effective, as anyone who has dealt with fungus growth in a
shower knows.
--Thymol crystals in a Dish, in an airtight Box, with the Item...Thymol is very
dangerous to Humans.....Leave for a few days, or a week.....Works well for Albums,
Prints, old negs and Slides..... Thymol Crystals from most scientific chemical
supply co.
--soaking the glass (not the metal!) in baths of a hydrogen peroxide-household
ammonia mixture, 50/50.
--high-intensity UV, a sunlamp, or even strong sunlight, these methods have mixed
success; modern lenses cemented with UV curing cements will absorb UV.
--negative ion generator (also known as ionizer) is the only sure fire way to
prevent mold
--alchohol to clean fungus off the glass.....the interior of the scope washed down
with a dilute solution of Chlorox (sodium hypochlorate) to kill all the mold
spores.
--periodically "gas" the components using formaldehyde gas. For example, remove
the optics, place in a zip-lock bag with some formalin (38%
formaldehyde)....formaldehyde may affect some components inside the lenses.
--enclose a teaspoon of paraformaldehyde powder in a small paper bag within the
microscope case....protects the microscope for a year or two and apparently has no
ill effect on lenses and the mechanical parts.
=====
Storage:
--a heated storage box....put several silica gel packets in the sealed
box....Drie-rite (CaSO4) can be corrosive.
--Parafilm wrapped around the lid of any old jar will keep indicator desiccant
blue for years.
--Tupperware brand is the best at sealing out humidity of all the commercial
sealable food storage containers.
--add N2 gas before sealing.
--do not store in leather or wood cases, which often promote fungus growth; store
in open air rather than any kind of case
--isolate lenses with fungus, don't store with uncontaminated glass.
Sources include: http://www.smu.edu/~rmonagha/bronfaults.html
http://www.smu.edu/~rmonagha/mf/fungus.html
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home page: http://home.europa.com/~telscope/binotele.htm