CAUSE AND PREVENTION OF MICROFILM BLEMISHES

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP75-00163R000100060027-3
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 9
• Document Creation Date: December 12, 2016
• Document Release Date: March 27, 2002
• Sequence Number: 27
• Publication Date: March 1, 1970
• Content Type: STUDY

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U.S."UErMl MME Of COMMERCE- Hatioral Bureau of Standards
Washington, D.C. 20234. V
FURTHER INFORMATION AVAILABLE FROM NBS OFFICE OF TECHNICAL INFORMATION AND PUBLICATIONS/PHONE [phone]
March 1970 - STR-3910
CAUSE AND PREVENTION OF MICROFILM BLEMISHES
IN BRIEF ... NBS has studied the cause and pre-
vention of microfilm blemishes. The study has
shown that blemishes result from an oxidation-
reduction reaction of the silver image by
peroxides and other gaseous products evolved
by the degradation of paper storage cartons.
Results of the study have indicated measures
for preventing microfilm blemishing.
A comprehensive study, by C. S. McCamy and C. I.
Pope of the NBS Institute for Basic Standards (U.S.
Department of Commerce), has revealed that gases evolved
from paper and paper-lined storage cartons are responsi-
ble for the formation of blemishes on processed micro-
ilm. 1/ Displacement of image silver has been pin-pointed
to an.oxidation-reduction reaction caused by peroxide
and other gases. The blemishes have become known,
therefore, as "redox blemishes." Fortunately, the study
has also indicated that simple precautionary measures
may be taken to eliminate redox blemishing.
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Several years ago, there were reports of the forma-
tion of spots or blemishes on processed microfilm. As a
great deal of information is stored on microfilm, this
was cause for alarm among film manufacturers, archivists,
Government agencies, and other records-keeping concerns.
The extent of the concern is illustrated by the number
of agencies that sponsored the research to solve the
problem. These were the National Archives and Records
Service, the Library of Congress, the Social Security
Administration, the Navy Bureau of Weapons, and the
Adjutant General's Office of the Department of the Army.
In addition, the National Microfilm Association solicited
and secured financial support from the Bell and Howell
Company, E. I. DuPont de Nemours and Company, Dynacolor
Corporation, International Business Machines, Minnesota
Mining and Manufacturing Company, Recordak Corporation,
University Microfilms, and Xerox Corporation.
When it became apparent that blemish formation was
2/
a widespread problem, a field surveyV was conducted in
which 100 trained inspectors examined over 7400 roles of
microfilm in different Government agencies. More than
370 000 observations were recorded and then statistically
analyzed at NBS. Among the findings of the survey were:
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blemishes existed in 6 different types; blemish forma-
tion was more severe in humid storage areas; films stored
in metal containers were practically blemish free; films
stored in air-conditioned areas were less prone to blem-
ish; and, when there were no leaders on the film rolls,
blemish formation was 2 to 3 times as severe as when
film rolls had leaders of approximately 1.5 meters.
These factors tended to confirm the theory that
products evolved from the paper storage cartons were re-
sponsible for blemish formation. Hydrogen peroxide is
evolved as paper degrades and the rate of this reaction
increases with the concentration of hydrogen peroxide.
To simulate this natural storage condition in the labora-
tory, paper was immersed in a 5 percent hydrogen peroxide
solution for thirty minutes, dried, and then sealed in
jars with specimens of films at approximately 80 percent
relative humidity. These films developed all the
naturally occurring blemishes within 30 days.
While this apparently confirmed the theory of per-
oxide induced-blemish formation, other observations were
3/
not explained. Studies elsewhere, for example, had
revealed that films fixed in solutions containing small
concentrations of iodide ions resisted blemish formation
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in actual storage. Such films, however, did form blem-
ishes in laboratory exposures to peroxide-treated paper.
This suggested that factors other than peroxide were
involved.
Further laboratory work was undertaken, which revealed
that formaldehyde and formic acid were also evolved from
the paper cartons. This work emphasized the fact that
the susceptibility of films to blemish formation in the
presence of peroxide is conditioned by other factors.
The silver grain, as formed in the gelatin matrix
during development, is inherently unstable. In the normal
photographic process, silver filaments become coated with
sulfur atoms during fixation. It is this coating that
stabilizes the grain structure. Films fixed a relatively
long time and films retaining a small amount of hypo after
washing acquire more sulfur and have been found to be
quite resistant to blemish formation when they are exposed
to peroxides, even at high humidity.
It was also found that when silver is oxidized and
reduced in the presence of chloride ions, the reduced
silver becomes incorporated with silver chloride in a
colloidal form. Laboratory demonstrations have shown
that a reddish colored colloidal silver is formed by the
reaction of hydrogen peroxide with pure metallic silver
in the presence of a small concentration of chloride ions.
The characteristic color of the blemishes has been attri-
buted to the presence of this colloidal. material.
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This suggested an investigation into the effects of
chlorine in the wash water on film stability. It was
found that films washed in distilled water were faded by
peroxide attack but typical blemishes did not form. A
small concentration of chlorine, therefore, appears to
be essential for formation of typical blemishes.
The study also revealed that the incidence of spots
increased with the optical density of the image. In one
experiment, a step tablet exposed to peroxide-treated
paper developed blemishes on all steps having densities
of 0.58 or more; none, however, formed at densities of
0.43 or less. The incidence of blemish formation also
increased for each step above 0.58.
While the differences in blemishing on various
brands of film were not significant, the processing
equipment was found to be an important factor. In fact,
the formation of blemishes on film processed by a partic-
ular machine so out-weighed the other statistics in the
survey that it became necessary to run a second analysis
without these data. Fortunately, this type of machine
is no longer on the market.
Results of the study have indicated several pre-
cautionary measures that may be taken to prevent blemish
formation:
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1. Use safety base permanent record film as specified
in the ANSI (formerly USASI) specifications for
photographic films for permanent records.
2. Use no higher densities than are required for the
intended purposes and use dark characters on a light
background if this is feasible.
3. Residual thiosulfate concentration should not exceed
1 microgram per square centimeter, but should be
greater than zero. The optimum concentration appears
to be about 0.5 microgram per square centimeter in a
clear area.
4. Keep processing machinery and film clean.
5. Avoid scratching film.
6. Store films in containers made of inert materials,
such as metals or plastics of proven quality. With
good ventilation and clean air, the containers need
not be sealed.
7. Do not permit storage temperature to exceed 70 OF
nor the relative humidity to exceed 40 percent.
8. Avoid wide-range cycling of temperature and humidity,
since this accelerates the imbibition of gaseous
contaminants.
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1/ McCamy, C. S., and Pope, C. I., Redox blemishes,
their cause and prevention, presented at the National
Microfilm Association Meeting held May 7, 1969,
Boston, Mass.
2/ McCamy, C. S., Wiley, S. R., and Speckman, J. A.,
A survey of blemishes on processed microfilm, J. Res.
Nat. But. Stand. (U.S.), 73A, 79 (1969).
Henn, R. E., Wiest, D. G., and Mack, B. D., Micro-
scopic spots in processed microfilm: the effects of
iodide, Phot. Sci. Eng. 9, 121 (1965).
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CAPTION FOR ILLUSTRATION:
Figure 1. Two types of microfilm blemishes are illus-
trated in these two microfilm enlargements.
An NBS study has shown that such blemishes are the result
of peroxides and other gases evolved by degradation of
paper cartons.
Photo:. 3910-1-3910
NOTE TO EDITOR: Glossy prints of the listed illustration
are available to editors upon request. Address the
National Bureau of Standards, Office of Technical Informa-
tion and Publications, Room A500/101, Washington, D.C.
20234,
.PLEASE DO NOT REFER TO THIS RELEASE BY NUMBER. The
number is for your information only. For reasons of
economy, the Bureau cannot undertake to comply with
requests from the public either for illustrations or
for copies of its releases. For further information,
we suggest you refer your readers to publications listed
in the footnotes to the release, or to the NBS Office
of Technical Information and Publications.
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