ISO 12206:1995

INTERNATIONAL
STANDARD
First edition
1995-02-01
Photography - Methods for the
evaluation of the effectiveness of Chemical
conversion of silver images against
Oxidation
Photographie - Mbthodes d ’baluation de I ’efficacitb de Ia conversion
chimique des images argentiques contre I ’oxydation
Reference number
ISO 12206: 1995(E)

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ISO 12206:1995(E)
Contents
Page
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 Scope 1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4 Dichromate bleach test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
5 Hydrogen peroxide incubation test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Annexes
A Correction of density values . 7
B Variables in silver stabilizing treatments . 9
C Significance of the test methods .
IO
D Bibliography . . 12
0 ISO 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, wrthout Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
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0 ISO
ISO 12206:1995(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical committees. Esch member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take patt in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 12206 was prepared by Technical Committee
ISOfTC 42, Photography.
Annex A forms an integral part of this International Standard. Annexes B,
C and D are for information only.
. . .
Ill

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0 ISO
ISO 12206:1995(E)
Introduction
Silver-gelatin Photographs have been used extensively for recording and
preserving information of lasting value in all fields of human activity. The
long-term stability of these records has become of increasing concern in
recent years, because image and support degradation have been found
with accelerating frequency in photographic collections and archives.
ISO has published documents on various aspects of the stability and
preservation of black-and-white silver-gelatin photographic materials. ISO
10602: 1995, Photography - Processed silver-gela tin type black-and-white
film - Specifications for stability, provides test methods and criteria for
the physical properties, permissible residual processing chemicals, and the
image quality of films. ISO 5466:1992, Photography - Processed safety
photographic films - Storage practices, deals with the conditions required
for maintaining and preserving the integrity of photographic films during
storage. ISO 10214:1991, Photography - Processed photographic ma-
- Hing enclosures for storage, pertains to the materials used in
terials
contact with stored photographic materials.
If photographic film meets the material and processing specifications of
ISO 10602 and is stored in accordance with ISO 5466 and ISO 10214,
excellent stability will be obtained. Similarly, photographic Paper prints
should be stored in accordance with ISO 6051:1992, Photography -
Processed photographic Paper prin ts - Storage practices, and processed
photographic plates in accordance with ISO 3897:1992, Photography -
Processed photographic pla tes - Storage practices.
However, in practical situations it is not always possible to control the
storage conditions, particularly with respect to contaminants.
Atmospheric pollutants such as Peroxides, Sulfur dioxide, ozone and ni-
trogen dioxide are very detrimental to silver imagesC11. Such environ-
mental pollutants are of increasing concern in our industrial Society. They
tan Cause Oxidation of the silver with consequent silver migration. This
results in image fading, silver mirroring and redox blemishesC*lW.
Oxidizing agents that diffuse out of enclosure materials Cause similar de-
fects.
Recent studies have shown that silver images tan be made resistant to
oxidizing pollutants by chemically treating the silver to form silver
sulfideL?l or silver selenideC51, or by Substitution of the silver by goldF1.
Such treatments are recommended when it is not possible to ensure the
absence of contaminants, or when the importante of the image justifies
the added expense.
This International Standard is an adjunct to the processing requirements
and describes methods for evaluating the effectiveness of various treat-
ments which impart greater stability to silver images.
IV

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INTERNATIONAL STANDARD 0 ISO ISO 12206:1995(E)
- Methods for the evaluation of the
Photography
effectiveness of Chemical conversion of silver images
against Oxidation
Members of IEC and ISO maintain registers of cur-
1 Scope
rently valid International Standards.
1 .l This International Standard describes methods
ISO 5-2: 1991, Photography - Density measurements
for evaluating the effectiveness of Chemical conver-
- Part 2: Geometrie conditions for transmission
sion treatments intended to increase the resistance
density.
of wet-processed silver images to Oxidation. The
treatment may be applied as part of the original pro-
ISO 5-3: --J, Photography - Density measuremen ts
cessing, or it may be a post-processing treatment.
- Part 3: Spectral conditions.
1.2 This International Standard applies to silver- ISO 5-4: -2), Photograph y - Density measuremen ts
gelatin images coated on to supports of either plastic, - Part 4: Geometrie conditions for reflection
Paper or glass. densit y.
1.3 lt does not recommend general or specific
3 Definitions
treatments for silver images. Likewise, treatment
temperature, times and replenishment rates are out-
For the purposes of this International Standard, the
side the scope of this International Standard. Factors
following definitions apply.
to be considered in a stabilizing treatment are
discussed in annex B. 3.1 treated silver images: Silver images that have
been given a specific treatment, either during or after
processing, to increase their stability.
1.4 This International Standard describes two test
methods: the dichromate bleach test and the hydro-
3.2 toned silver images: Silver images that have
gen peroxide incubation tesV1. The significance of
been given a specific treatment, either during or after
each is discussed in annex C.
processing, to modify their colour.
2 Normative references
4 Dichromate bleach test
The following Standards contain provisions which,
through reference in this text, constitute provisions 4.1 Principle
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All Standards This test consists of dissolving the treated silver im-
are subject to revision, and Parties to agreements age and measuring the retained density. This retained
based on this International Standard are encouraged density is proportional to the silver that has been
chemically converted to a non-bleachable compound,
to investigate the possibility of applying the most re-
or has been substituted by a non-bleachable element.
cent editions of the Standards indicated below.
1) To be published. (Revision of ISO 5-3:1984)
2) To be published. (Revision of ISO 5-4:1983)

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0 ISO
ISO 12206:1995(E)
density (after treatment but before bleaching) and
4.2 Reagents
multiplying by 100. Make this calculation for all six
uniform-density patches.
4.2.1 Bleach solution
With some photographic materials, particularly photo-
A bleach Solution shall be prepared by dissolving
graphic Paper prints, bleaching tan Cause an increase
90 g of anhydrous potassium dichromate in 1 litre of
in the D,i ”. The percent density retention shall be
water. Subsequently, 96 ml of concentrated sulfuric
corrected for any D,i, increase, as shown in
acid shall be slowly added with constant stirring.
annex A.
WARNING - Avoid contact with the eyes, skin
and clothing. Wash thoroughly after handling. In
4.6 Significance
case sf contact, flush eyes and skin with water.
Obtain medical attention immediately. The retained density is an approximation of the per-
centage of silver image that has been converted into
Take care to dispose of dichromate bleach sol-
substances which are not affected by oxidants or
ution in accordance with national and local haz-
pollutants. A treatment which results in 65 % density
ardous waste disposal regulations.
retention or more after bleaching for all six density
patches is considered a stable image3).
4.22 Clearing Solution
5 Hydrogen peroxide incubation test
The Clearing Solution shall be prepared by dissolving
100 g of sodium sulfite in 1 litre of water.
5.1 Principle
4.3 Specimen preparation This test consists of exposing the treated silver im-
ages to hydrogen peroxide vapour and measuring the
Six uniform-density patches shall be prepared on the
resultant Change in density. A small Change in density
treated silver material with densities (D) ranging in
represents an image that is resistant to Peroxides.
approximately equal increments from 0,l above D,i”
The exact size of the patches is not critical,
t” 4lw
5.2 Reagents
provided they cover the aperture of the densitometer
and are easy to handle.
5.2.1 Hydrogen Peroxide, reagent grade,
2 % (m/m) Solution, freshly prepared from a 30 %
stock Solution.
4.4 Procedure
WARNING - Hydrogen peroxide is very corrosive.
Measure the treated silver image on the six uniform-
Caution should be used in handling hydrogen
density patches and on D,i” for Status A blue density.
peroxide solutions. The stock solutions should be
Densities shall be measured on a densitometer having
kept refrigerated in vertical vented bottles and
spectral conformance to ISO 5-3. The densitometer
kept away from combustibles. Gloves and protec-
shall have geometric conformance to ISO 5-2 for
tive clothing should be worn.
photographic films and plates, and geometric con-
formante to ISO 5-4 for photographic Papers.
Take care to dispose of hydrogen peroxide sol-
utions according to national and local waste dis-
Then immerse the specimen in the bleach Solution
posal regulations.
(4.2.1) for 30 s at (20 + 5) “C, rinse it in water for
2 s, and clear for 30 s in the Clearing Solution (4.2.2).
5.2.2 Potassium chloride, saturated Solution.
Then rinse the specimen in water, dry it and re-
measure the Status A blue density.
5.2.3 Potassium chloride, dry solid.
5.3 Apparatus
4.5 Calculation
The components of the desiccator jar used to expose
The percent density retention is calculated by dividing
the test specimens to hydrogen peroxide vapour are
the blue density after bleaching by the original blue
3) This density retention value is based on the fact that since two-thirds of the image will not be affected by oxidants, ther-e
would be no loss of information. Treatments which result in a lower percent density retention may also be very stable, de-
pending upon the image density and the type of Chemical conversion.

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0 ISO
ISO 12206:1995(E)
given in figure 1 and the assembled apparatus is four fan blades, each approximately 25 mm in length.
shown in figure2. lt consists of the following el- The fan shall rotate at approximately 2 000 r/min.
ements.
5.3.3 Plastic4) collar, which shall fit snugly inside
Glass desiccator jar, having a nominal inside
5.3.1
the desiccator on which the specimens are mounted.
diameter of 150 mm and a capacity of 2 litres.
The collar shall be roughly 80 mm in height with an
5.3.2 Ground plastic4) desiccator lid, fitted with a
inside diameter of 135 mm and a wall thickness of
fan .
approximately 7 mm. The collar shall be fitted with
The fan motor is attached to the top surface of the three baffles, each approximately 80 mm in length,
desiccator lid with the shaft going through the lid to 20 mm in depth, and 25 mm in width? A plan draw-
the fan mounted on the inside surface. There shall be ing of the collar and baffles is shown in figure3.
Figure 1 - Desiccator jar components
Poly(methyl methacrylate) has proved to be an acceptable plastic.
4)
5) The ba ffles serve to provide more turbulent air moveme nt and ensure uniform distribut ion of the hydrogen peroxide vapour.
be constructed of a hydrogen-Peroxide-resistant such a
They m plastic, s polycarbonate.
aY
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ISO 12206:1995(E)
Figure 2 - Assembled desiccator jar
5.3. 4 Perforated porcelain plate, of diameter
54 . Specimen preparation
140 mm, which fits over the desiccator weil.
Six uniform-density patches shall be prepared with
densities (D) ranging in approximately equal in-
crements from 0,l above D,i, to D,,,. The exact size
5.3.5 Petri dish, of capacity 60 ml, which fits into
of the patches is not critical, provided they cover the
the desiccator weil and which holds a saturated salt
aperture of the densitometer and are easy to handle.
Solution to regulate the relative humidity.
5.5 Procedure
5.3.6 Circular pad, approximately 40 mm in diam-
eter, of 0,3 mm chromatography Paper or filter 5.5.1 Measure the Status A blue density on the six
papeP, with a water flowrate of 100 mm to 150 mm uniform-density patches and on Amin before treat-
per 30 min71 which is wired to the upper side of the ment. Densities shall be measured on a densitometer
perforated p ’orcelain plate with stainless steel wire. having spectral conformance to ISO 5-3. The
densitometer shall have geometric conformance to
ISO 5-2 for photographic films and plates and ge-
ometric conformance to ISO 5-4 for photographic pa-
5.3.7 Oven, fan-assisted, capable of being main-
pers.
tained at 50 “C + 2 “C.
-
6) A suitable chromatography Paper is Whatman No. 3 mm CHR Paper. This information is given for the convenience of users
of this International Standard and does not constitute an endorsement by ISO of the product named. Equivalent products may
be used if they tan be shown to lead to the same results.
7) This refers to the capillary rise of water when the Paper is partially immersed in water.
4

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ISO 12206:1995(E)
Figure 3 - Drawing of collar and baffies
5.5.5 Seal the desiccator jar (53.1) with its cover
5.5.2 Attach the specimens with the base side
and place it in the oven (5.3.7) set at 50 “C. The fan
against the inside surface of the cylindrical coIlar*).
shall be turned on for the first 30 min to distribute the
Take care to ensure that the specimens are snug
peroxide vapour uniformly.
against the collar surface.
Remove the jar from the oven, quickly Charge
5.5.3 Place 5 ml of a saturated Solution of potassium 5.5.6
it with the addition of a second 0,12 ml of freshly
chloride (5.2.2) in the Petri dish (5.3.5) to achieve a
relative humidity of 82 %. To maintain Solution satu- prepared hydrogen peroxide Solution (5.2.1) without
allowing the desiccator jar to cool to room tempera-
ration, add 10 g of dry potassium chloride (5.2.3) to
ture. Replace it in the oven set at 50 “C. Turn on the
the Petri dish.
fan for a second 30 min. The desiccator jar shall then
be incubated with the fan turned off for 17 h at
5.5.4 Charge the desiccator by the addition of
50 “C, resulting in a total incubation of 18 h.
0,12 ml of the hydrogen peroxide Solution (5.2.1) to
the pad of chromatography Paper (5.3.6). This gives a
5.5.7 Remove the specimens from the desiccator jar
peroxide concentration of approximately 1 000 ppm.
8) If the baffles are constructed so that they are spring loaded, the specimens tan be attached by inserting the edges under
the baffles.
5

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ISO 12206:1995(E) 0
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