1
Bull. Soc. Photogr. Imag. Japan. (2015) Vol. 25 No. 1: 1–6

Original Paper

Influence of Fumigation on Photographic Images and Their Stability
in Long-Term Preservation
Takako Yamaguchi*, ***, Toshiaki Kawamata**, Fumiyuki Shiba***, Yusuke Okawa***

Abstract:

The influence of fumigation on several types of photographic images and a colloidal silver film was examined using various
fumigants (propylene oxide, ethylene oxide, methyl iodide, sulfuryl fluoride, cyphenothrin, methyl bromide, and carbon dioxide).
The effect on the long-term stability of the images was also examined via accelerated aging experiments on the fumigatedsamples. Although methyl iodide and bromide are known to react with colloidal silver, these reagents did not affect photographic
silver images. The other fumigants also negligibly affected all of the photographic specimens examined. Even when long-term
storage tests were conducted, fumigation did not cause notable changes to typical photographic images.

Key words:

Gelatin, Fumigation, Aging, Photographic image

1. Introduction
Throughout history, proteins, gelatin and albumin have beenused as the primary photographic binders. Under humid conditions, binders undergo not only physicochemical deterioration,
but also biological deterioration due to mold. In order to avoid
biological­deterioration, fumigation is generally applied to mostcultural properties prior to storage in museums. To date, however,fumigation has not been used on photographs. Methyl bromide(MeBr) has been widely used in combination with other fumigants to enhance the characteristic merits and to compensate forthe weak points of each reagent 1). Use of a mixture of methyl
bromide and ethylene oxide (MBEO, one of the most common
fumigation agents) is known to be effective against both insects
and bacteria for in cultural properties for extended periods oftime. It has been reported that MBEO affects sulfur-containing
materials, and it has therefore been suspected that similar chemical reactions would take place with photographic materials 2).
However, museum conservators desire fumigation treatment ofphotographs of cultural importance because all such resources are
generally kept in the same physical storage space. It is therefore
necessary for our museums to understand the effects of fumigation on photographic images. This work evaluates the applicabilityof various fumigants to various types of photographs.
MeBr was historically one of the most widely-used soil fumigants, but the “Montreal Protocol on Substances that Deplete the
Ozone Layer” identified MeBr as an ozone depleting substance.
In 1997, it was agreed that the use, sale, and production of
MeBr would be totally prohibited by 2005 in advanced countries,

including Japan 3).
A mixture containing MeBr has been widely used for the fumigation of cultural properties in museums, because it works incredibly well to protect against damage from insects, bacteria, andfungi. However, following the Montreal Protocol, various alternative fumigants have been increasingly used. The effects of various
pesticides, ovicides, and fungicides on a wide variety of cultural
artifacts — from inorganic materials such as metals to organic
materials such as zoological specimens — have been examined byseveral groups 2, 4–7).
However, the effects on photographic images of these major­f umigants have not been reported. Although photographs are notcurrently fumigated to avoid fouling the images, conservators
must be diligent in order to avoid contaminating other museum
acquisitions with material from non-fumigated photographs. (Ofcourse, since biological deterioration does occur on photographs,
fumigation would also be an attractive way to conserve the photographs themselves.) In view of this, the effects of major fumigants
on a wide variety of photographic images were examined. In orderto evaluate these effects under practical museum conditions, theexperiments shown in Scheme 1 were planned, and the following
evaluations were conducted on a variety of types of unalteredphotographic samples (Stage i):(1) Direct effects of fumigation on photographic images (Stage ii)(2) Effects after long-term preservation of the fumigated photographic images (Stages iii and vi)(3) Effects of re-fumigation (Stage iv)(4) Effects after long-term preservation of the re-fumigated photographic images (Stage v).

Received: 19th, August 2014; Accepted: 1st, January 2015
*Tokyo Metropolitan Museum of Photography, 1-13-3 Mita, Meguro-ku, Tokyo 153-0062, Japan**Faculty of Engineering Chiba University, Yayoicho 1-33, Inage-ku, Chiba-shi, Chiba 263-8522, Japan***Graduate School of Advanced Integration Science, Chiba University, Yayoicho 1-33, Inage-ku, Chiba-shi, Chiba 263-8522, Japan

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Bull. Soc. Photogr. Imag. Japan. Vol. 25 No. 1 (2015)

Scheme 1. Flow chart of experiments and stages of fumigation and aging.

Stage iii is considered to be the situation after the loan out ofmuseum works, as fumigation is preferred before re-storage.

2. Materials and Methods
2.1 Photographic Samples
Various types of photographs (from conventional to modern/digital-based; Fig. 1 and summarized in Table 1) were treatedwith a fumigant. Samples Fiber-base gelatin silver print (FB) andResin coated gelatin silver print (RC) were contact exposed to thetungsten-halogen lamp filtered by a UV filter with Kodak Photographic Step Tablet no. 2 (uncalibrated; hereafter referred to as“Step Tablet”), then were developed with Kodak’s D72 diluted
1:2 with water, fixed with Kodak F-5, washed and dried. Recipesof Samples Albumen print (AP) and Cyanotype (CT) are indicated in Tables 1 and 2. Images on them were produced as photographs contact-printed out with Step Tablet with the metal halidelamp, then were washed, fixed with Kodak F-5, washed and dried.
Sample Ink-jet print (IJ) was printed by a printer Epson PMG720 with digital data that has been copied from the Macbeth
ColorChecker Chart. Sample Chromogenic print (CP) was also
printed from the same digital data.
A colloidal silver film (CS, colloidal silver in gelatin on a polyester film base) was utilized as a sensitive sensor to detect substances affecting the silver image. CS is commonly used to test
photograph storage enclosure materials 8), and is reported to be oneof the most sensitive materials under the incubation conditions 9).

2.2 Fumigation
The fumigant characteristics and fumigation conditions are
summarized in Table 4. The fumigation conditions are essentiallybased on the specifications of the Institute of Insect Damage to
Cultural Properties 1). The primary MeBr substitutes were examTable 2. Ingredients of Albumen
print.

Fig. 1.

Photographic samples examined.

Table 1.

Table 3. Ingredients of
Cyanotype.

Sizing/salting solution is:
45 g albumin
7 g sodium chloride
150 ml distilled water

Mixing Sensitizer;
Solution A is:
20 g ferric ammonium citrate
100 ml distilled water

Sensitizer is:
10 g silver nitrate
2 drops 1N nitric acide
100 ml distilled water

Solution B is:
9 g potassium ferricyanide
100 ml distilled water

Constituent materials and manufacturers of photographic samples examined.

SampleManufacturer

BinderSupport

Image material

Ink-jet print (IJ)

Photofinishing, Advance Hi Double weight,
Fujifilm and Epson PM-G720

polymerresin coated paper

dye

Chromogenic print (CP)Kodak paper

gelatinresin coated paperdyeGelatin silver print (FB)

Fuji Bromide Rembrandt VG2, Fujifilm

gelatinfiber-based paper

silverGelatin silver print (RC)Super SP Gekko VR 2, Mitsubishi Paper
Mills Limited

gelatinresin coated paper

silverAlbumen print (AP)hand madealbumenacid-free paper(Tokushu Paper Mfg.)

silverCyanotype (CT)hand made—acid-free paper(Tokushu Paper Mfg.)

iron compounds

Colloidal silver film (CS)Agfa-Gevaert

gelatinpolyester film

silverGelatin dry plate (GD)

unknown

gelatinglass

silverNitrocellulose film (NC)unknown

gelatincellulose nitrate film

silverYamaguchi, Kawamata, Shiba, and Okawa   Influence of Fumigation on Photographic Images and Their Stability in Long-Term Preservation

Table 4.

3

Treatment conditions of samples.

Fumigant or treatment

Temperature°C

Humidity%RH

Concentration

Treatment time

Effects

Mixed methyl bromide and ethyleneoxide reagent (MBEO) a)

25.0

40

98–92 g/m3

48 hours

insect repellent, bacterial killing

Methyl iodide (MI) b)

18.0

54–59

1.1–2.1%

48 hours

insect repellent, bacterial killing

Propylene oxide (PO) c)

17.5–18.0

52–59

2.0–2.3%

48 hours

insect repellent, bacterial killing

Ethylene oxide (EO) d)

18.0–18.5

54–60

2.6–2.7%

48 hours

insect repellent, bacterial killing

Sulfuryl fluoride (SF) e)

25.0

40

48–54 g/m3

48 hours

insect repellent

Mixture of cyphenothrin and carbon
dioxide (CPT) f)

23.0

40

48–54 g/m3

4 hoursa pyrethroid insect repellent

Carbon dioxide, condition A (CO2A)

25.0

not controlled(ca. 33)

60 v/v%

14 days–

Carbon dioxide, condition B (CO2B) g)

25.0

50

60 v/v%

14 daysinsect repellent

Carbon dioxide, condition C (CO2C)

25.0

<1

100%

14 days–

Carbon dioxide, condition D (CO2D)

25.0

>85

100%

14 days–

ined: MI 10), PO 11, 12), EO 13), SF 14, 15), and CPT 16). CO2 wasalso used 17–19). As MeBr remains in limited use in some areasand has been applied to some photographs, a MeBr-EO mixed
fumigant (MBEO) was also tested.
2.3 Accelerated aging
Accelerated aging/deterioration tests were attempted in order tosimulate long-term preservation. The tests were conducted according to ISO 18916 8). Samples IJ and CP were stored at 60°C (because dyes may sublime at elevated temperatures) and 86%RH for
2 weeks, and Samples FB, RC, AP, CT, CS and GD at 70°C and
86%RH for 2 weeks 8). The incubation period is 15 days in ISO,but the incubation in this report was performed in 2 weeks due tothe schedule.
2.4 Evaluation
For Samples IJ, CP, FB, RC, AP, and CT, the reflection density
and the CIELab value were measured with a spectrophotometer(Spectrolino, GretagMacbeth), and the corresponding color differences were calculated. For transmitting Samples CS, GD, andNC, the transmission densities were measured with a densitometer (TR-924, Macbeth). The density measurements were performed under conditions optimized to the nature of each sample
for maximizing the sensitivity to the variation: ISO visual density(Dv) for Samples FB, RC, GD and NC, blue filtered density of
Status A (Db) for Samples AP and CS, and red filtered density of
Status A (Dr) for Sample CT.

transmission spectrum of CS before and after fumigation with
MBEO or MI. For halogen-containing fumigants, the colloid­silver chemically reacts with the halogen atom and the spectral
properties are perturbed, resulting in an increased Db value. Thechange in transmission density before vs. after fumigation for theother transmitting samples was less than ± 1% (e.g. 0.58 → 0.58,
0.90 → 0.91 for GD; 0.97 → 0.97, 1.68 → 1.69 for NC). As CS isconsidered to be a very sensitive detector for substances that reactwith silver, potential effects of halogenous fumigants cannot be
entirely ruled out, but they are certainly insignificant for MeBr
and MI.
Fig. 3 shows the change in density before and after fumigation
for AP and FB silver images. No significant density change wasseen after fumigation for any fumigant, regardless of density level.
Table 5 shows the color differences before and after fumigationin yellow, magenta, cyan, and black patches of CP. Following
CO2B and EO treatments, a small but similar level of discolor-

ation was observed for all colors. Although these results suggest
some chemical influence on the dye images from these fumigants,
the changes were well balanced and as noted below, practically

3. Results and Discussion
3.1 Influence of fumigation processes on photographic images(Stage ii)
CS fumigated with MBEO or MI exhibited a 4–6% increase inblue-filtered density (Db), although no change was observed as aresult of the other fumigants. Fig. 2 shows the change in theFig. 2. UV/V is transmittance of CS before and after fumigation.

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Bull. Soc. Photogr. Imag. Japan. Vol. 25 No. 1 (2015)

Fig. 3. Comparison of (a) AP and (b) FB with several other fumigants.

Table 5.
Fumigant or treatment
MBEO
MI
PO
EO
SF
CPT
CO2A
CO2B
CO2C
CO2D

Color difference of chromogenic print with fumigation.
Color difference of sample after first fumigation / after re-fumigation

Yellow ΔE

Magenta ΔE

Cyan ΔE

Black ΔE

0.20 / –0.76 / 0.73
0.87 / 1.43
0.67 / 0.69
0.09 / 0.15
0.25 / 0.23
0.07 / –0.31 / 0.34
0.44 / –0.60 / –0.51 / –0.34 / 0.54
0.56 / 0.85
0.58 / 0.55
0.45 / 0.48
0.44 / 0.40
0.30 / –0.33 / 0.29
0.74 / –0.52 / –0.20 / –0.32 / 0.29
0.36 / 0.85
0.67 / 0.65
0.16 / 0.18
0.26 / 0.40
0.19 / –0.23 / 0.29
0.22 / –0.38 / –0.24 / –0.27 / 0.40
0.13 / 0.30
0.16 / 0.15
0.28 / 0.25
0.30 / 0.56
0.15 / –0.34 / 0.12
0.35 / –0.19 / –*For abbreviations, see Table 4.

insignificant. Following PO and MI treatments, the discolorationof yellow was somewhat larger than the other colors. After treatment with SF, MBEO, and CPT, the discoloration of magenta
was larger. However, all of these changes are small relative togeneral visual recognition – few people can discern a color difference less than 0.6 even upon intense scrutiny, and in casual viewing, an acceptable color difference (taking into account various
factors) is 1.2 20).
3.2 Verification of image stability in long-term preservation(Stage vi)
Figs. 4 and 5 illustrate the influence of fumigation on AP and
CT images after accelerated aging. For AP, a different trend wasfound for CPT as compared to the other fumigants in the low image density region, as indicated by the circled area in Fig. 4(b).
Except for CPT, discoloration of the silver image after aging
counterbalances the growing yellowness of the base paper, resulting in a suppressed density decrease after aging in this region. On
the other hand, CPT might inhibit yellowing of the base paperand binder albumin. While the mechanism is uncertain, no effecton the silver image itself was also confirmed.

3.3 Influence of the re-fumigation processes on photographic
images and long-term preservation (Stages iv, v)
Regular, repeated fumigation of resources is required for longterm preservation and should be applied after exposure to any outof-museum-storage atmosphere. In order to evaluate the influenceof re-fumigation on photographic images, a second fumigation
treatment was carried out on the fumigated samples about one
year after the first fumigation. The second treatment conditions(temperature, humidity, and fumigant concentration) were essentially identical to the ones described in section 2.1, although
MBEO treatment could not be conducted because of legal prohibitions. For CO2 treatment, the most popular CO2B conditions
were applied. In order to evaluate the influence on photographic
images in long-term preservation, accelerated aging experiments
were also applied to the twice-fumigated samples (Stage v).
Table 5 shows both the color differences before and after the
first fumigation and re-fumigation in yellow, magenta, cyan, andblack patches of CP. Fig. 6 shows the CS transmission density­before and after re-fumigation and accelerated aging. No significant
changes were detected following re-fumigation, unless the fumigant contained iodine, which causes chemical degradation of thecolloidal silver and specific changes in the transmission density. TheYamaguchi, Kawamata, Shiba, and Okawa   Influence of Fumigation on Photographic Images and Their Stability in Long-Term Preservation

Fig. 4.

Fig. 5.

5Influence on AP with fumigation and with accelerated aging.

Influence on CT with fumigation and with accelerated aging.

criteria specified in ISO 18916 indicate that the change in CS after
accelerated aging must not exceed ±20% of the standard sample.
Only MI exceeded this threshold. The sensitivity of CS is very
high as a sensor. Thus, at least in a practical context, (except forMI) re-fumigation­does not affect image stability for a wide variety of photographic images. In conclusion, upon treatment witheach fumigant, all of the samples (other than CS fumigated withCPT) showed no significant difference in both density and color.
Furthermore, fumigation did not affect the long term stability of
the images upon accelerated aging. For the first time, significant
practical data has been acquired for works museums actually handle.
The same experiments were conducted on gelatin dry plates (GD)
and nitrocellulose films (NC) that were produced more than 50
years ago. The storage environment and other details of thesesamples are unknown. The samples showed no significant changes
after fumigation for all of the fumigants examined. The GD sample was then stored under the accelerated aging conditions, and no
significant changes were observed (the accelerated aging test
was not conducted for the NC sample because of the risk of spontaneous combustion). These results are consistent with the results
found for the more modern samples. The older samples may beprotected from the fumigants by some degradation due to age (influence of hardened gelatin, exhaust/pollution in the atmosphere,etc), although this has not yet been proven. At the very least, theseresults strongly suggest that fumigation of old works having an
uncertain storage history does not affect image quality, thoughfurther studies with other old photographs using other photographic techniques is of course recommended (and ongoing).

Fig. 6. CS density at all experimental stages with various fumigants (The control sample was examined after aging (Stage iii), after accelerated aging (Stagevi) and after aging followed by accelerated aging (Stage v) without any fumigant applied at any point.) Initial density Db0 = 3.23.
*Not tested because fumigant was commercially discontinued.

6Bull. Soc. Photogr. Imag. Japan. Vol. 25 No. 1 (2015)

4. Conclusion and Future Studies
The effects of the primary fumigants currently being used and/or recognized as useful for the preservation of cultural properties
were examined, specifically the effect on image quality of photographs processed using the primary photographic techniques.
Negligible changes in density and color were observed, and thus,
it can be concluded that fumigation does not affect the images.
No effect on image quality for long-term preservation following
fumigation was also confirmed, and residue from the fumigant is
negligible or, at least, does not affect stability. These residue tests
will be the subject of a future publication. Re-fumigation treatment has little effect on images processed using the major photographic techniques, at least using the appropriate fumigants andprocedures. No apparent problem was found upon repeated fumigation, at least using an interval of one year. Over such a time, residual fumigant on the photographs completely diffuses into theatmosphere, and hence, any influence of the residue was found tobe negligible. Of course, it is necessary to devote some attention
to the selection of fumigant because there are chemicals whichcause significant density deterioration (such as CPT in the low
density range), and colloid silver reacts with halogens.
When considering these results, the following should be kept
in mind: (1) the samples used in this study were generally modern(and hence, rather durable) photographic materials – classical­photographs may contain more sensitive materials; (2) image deterioration takes place due to a wide variety of causes, including
an oxidative/reductive storage environment and residual chemicals
from photographic processing; and (3) residues from fumigants
and/or photographic processes may act synergistically resulting
in severe effects on image quality. Combinations of fumigants(including ones not tested here) should be carefully examined, as
well as photographic materials prepared with techniques not tested in this study.
The recent total ban of methyl bromide has increased the number of museums using Integrated Pest Management (IPM), which
requires daily action, instead of occasional fumigation to control
insects and fungi. 21) In order to avoid insect damage, two storage

conditions are known to be effective: (1) low oxygen concentration (0.1% or less), and/or (2) low temperature (from –30°C to–20°C) 22–24). The former method may have the additional benefitof preventing oxidative degradation of images. However, the lattermethod must be re-examined for use with the storage of photographs due to the possibility of microscopic damages (e.g. the effect on a gelatin layer) caused by the freezing.

Acknowledgment
The authors thank Ekika Carbon Dioxide Co. (Tokyo, Japan),
Air Water Inc. (Osaka, Japan), and Kanto Kogyo Co. (Yokohama,Japan) for their cooperation of the fumigation treatments.

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