ISO 18927:2013
(Main)Imaging materials — Recordable compact disc systems — Method for estimating the life expectancy based on the effects of temperature and relative humidity
Imaging materials — Recordable compact disc systems — Method for estimating the life expectancy based on the effects of temperature and relative humidity
ISO 18927:2013 specifies a test method for estimating the life expectancy of information stored on recordable compact disc systems. Only the effects of temperature and relative humidity on the media are considered.
Matériaux pour image — Systèmes de CD enregistrables — Méthode d'estimation de l'espérance de vie basée sur les effets de la température et de l'humidité relative
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INTERNATIONAL ISO
STANDARD 18927
Third edition
2013-03-01
Imaging materials — Recordable
compact disc systems — Method for
estimating the life expectancy based
on the effects of temperature and
relative humidity
Matériaux pour image — Systèmes de CD enregistrables —
Méthode d’estimation de l’espérance de vie basée sur les effets de la
température et de l’humidité relative
Reference number
ISO 18927:2013(E)
©
ISO 2013
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ISO 18927:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
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ISO 18927:2013(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Purpose and assumptions . 4
4.1 Purpose . 4
4.2 Assumptions . 4
5 Measurements . 4
5.1 Summary . 4
5.2 Block error rate (BLER). 4
5.3 Test equipment . 5
5.4 Test specimen . 5
6 Accelerated stress test plan . 6
6.1 General . 6
6.2 Stress conditions . 7
6.3 Accelerated test cell sample population . 9
6.4 Time intervals .10
6.5 Test plan .10
6.6 Measurement conditions . .10
7 Data evaluation .10
7.1 Lognormal distribution model .10
7.2 Eyring acceleration model .11
7.3 Acceleration factors .12
7.4 Survivor analysis .12
7.5 Aids .12
8 Disclaimer .12
Annex A (informative) Step analysis outline .13
Annex B (informative) Example of test plan and data analysis .14
Bibliography .26
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ISO 18927:2013(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. Each 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 part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18927 was prepared by Technical Committee ISO/TC 42, Photography.
This third edition cancels and replaces the second edition (ISO 18927:2008), of which it constitutes a
minor revision.
The following change has been made to the second edition:
— An update of the bibliographical references.
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INTERNATIONAL STANDARD ISO 18927:2013(E)
Imaging materials — Recordable compact disc systems —
Method for estimating the life expectancy based on the
effects of temperature and relative humidity
1 Scope
This International Standard specifies a test method for estimating the life expectancy of information
stored on recordable compact disc systems. Only the effects of temperature and relative humidity on
the media are considered.
This International Standard does not cover the effects of light, air pollution, or time-dependent flow
phenomena.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
1)
ISO/IEC 10149 , Information technology — Data interchange on read-only 120 mm optical data disks (CD-ROM)
IEC 60908, Audio recording — Compact disc digital audio system
Experimental statistics, U.S. National Bureau of Standards Handbook 91, 1963
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
baseline
condition representing the disc at time of manufacture
Note 1 to entry: This is customarily the initial parameter measurement taken prior to any application of stress.
The designation is usually t = 0 for a stress time equal to zero hours.
3.2
block error rate
BLER
ratio of erroneous blocks to total blocks measured at the input of the first (C1) decoder (before any error
correction is applied)
Note 1 to entry: The more commonly reported value for BLER is the number of erroneous blocks per second
measured at the input of the C1-decoder during playback at the standard (1X) data rate.
[IEC 60908]
3.2.1
maximum block error rate
max BLER
maximum BLER measured anywhere on a disc
1) Equivalent to ECMA 130.
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ISO 18927:2013(E)
3.3
compact disc-recordable
CD-R
recordable optical disc in which information can be recorded to certain areas in compact disc format
Note 1 to entry: Information can be recorded once and read many times.
Note 2 to entry: The term “compact disc-write once” (CD-WO) has also been used to describe this type of disc.
3.4
cumulative distribution function
Ft()
probability that a random unit drawn from the population fails by time t, or the fraction of all units in
the population which fails by time t
3.4.1
lognormal cumulative distribution function
Ft()
cumulative distribution function in which the logarithm of the relevant parameter, in this International
Standard the disc lifetime, has a normal distribution and is defined by the following equation:
ln()x −μ
t
2
1 l
− ()
1 1
2 σ
l
Ft()= edx
∫
σ x
2π
l
0
where
t is the time;
x is a variable representing disc lifetime;
σ is the log standard deviation;
l
μ is the log mean;
l
ln(x) is the natural logarithm of x
μ
1
Note 1 to entry: When t =e , the lognormal cumulative distribution function evaluates to 0,5. In other words,
the model predicts that half the samples have failed at that time.
3.5
disc-at-once recording
method of recording a CD-R disc whereby the entire CD is recorded in one pass without turning off the laser
3.6
end-of-life
occurrence of any loss of information
3.7
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having permanent value
3.8
glass transition
reversible change in an amorphous polymer from, or to, a viscous or rubber condition to, or from, a hard
and relatively brittle one
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ISO 18927:2013(E)
3.8.1
glass transition temperature
T
g
approximate mid-point of the temperature range over which glass transition takes place
Note 1 to entry: T can be determined readily only by observing the temperature at which a significant change
g
takes place in a specific electrical, mechanical, or other physical property.
Note 2 to entry: T can also be sensitive to the moisture content of the polymer.
g
3.9
information
signal or image recorded using the system
3.10
life expectancy
LE
length of time that information is predicted to be acceptable in a system after dark storage at 23 °C and
50 % relative humidity (RH)
3.10.1
standardized life expectancy
SLE
minimum life span, predicted with 95 % confidence, of 95 % of the product stored at a temperature not
exceeding 25 °C and a relative humidity (RH) not exceeding 50 % RH
3.11
retrievability
ability to access information as recorded
3.12
stress
experimental variable to which the specimen is exposed for the duration of the test interval
Note 1 to entry: In this International Standard, the stress variables are confined to temperature and relative humidity.
3.13
survivor function
Rt()
probability that a random unit drawn from the population survives at least time t, or the fraction of all
units in the population which survive at least time t
Note 1 to entry: Rt()=−1 Ft().
3.14
system
combination of material, hardware, software, and documentation necessary for recording and/or
retrieving information
3.15
test cell
device that controls the stress to which the specimen is exposed
3.16
track-at-once recording
method of recording a CD-R disc whereby each track is recorded individually with 150 empty sectors
immediately preceding it and two run-out sectors immediately following
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ISO 18927:2013(E)
3.17
uncorrectable error
error in the playback data that is not correctable by the cross interleave Reed-Solomon code defined in
IEC 60908 as implemented in a system
4 Purpose and assumptions
4.1 Purpose
The purpose of this International Standard is to establish a methodology for estimating the life
expectancy of information stored on recordable compact disc systems. This methodology provides a
technically and statistically sound procedure for obtaining and evaluating accelerated test data.
The methodology deals only with the effects of temperature and humidity on the retrievability of
stored information. For this reason, this International Standard is primarily directed to those storage
applications, e.g. libraries and archives, in which exposure to other influences potentially detrimental
to information life expectancy, such as chemical agents, intense light sources, and improper handling, is
controlled and minimized.
4.2 Assumptions
The validity of the procedure defined by this International Standard relies on three assumptions:
— specimen life distribution is appropriately modelled by the lognormal distribution;
— the kinetics of the dominant failure mechanism is appropriately modelled by an Eyring
acceleration model;
— the dominant failure mechanism acting at the usage condition is the same as that at the
accelerated conditions.
Publications by Hamada and Stinson provide data indicating that these assumptions are applicable to
[5] [6]
compact disc-recordable (CD-R) systems (see references and in the Bibliography).
5 Measurements
5.1 Summary
A sampling of 80 recorded discs shall be divided into five groups according to a specified plan. Each
group of discs (test cell) shall be subjected to one of five test stresses, combinations of temperature and
relative humidity. Periodically during the stress conditions, all discs from each stress group shall have
their block error rate (BLER) measured. Data collected at each time interval for each individual disc are
then used to determine a lifetime for that disc.
The disc lifetimes at each stress level are fitted to a lognormal distribution to determine a mean lifetime
for the stress. The resulting five mean lifetimes are regressed against temperature and relative humidity
according to an Eyring acceleration model. This model is then used to estimate the distribution of
lifetimes at a usage condition.
5.2 Block error rate (BLER)
End-of-life is the occurrence of any loss of information. Ideally, each specimen is tested until the first
loss of information occurs. Realistically, this is impractical. This International Standard considers max
BLER to be a high-level estimate of the performance of the system. The objective of measuring BLER is
to establish a practical estimation of the system’s ability to read recorded data without uncorrectable
errors. A change in max BLER in response to the time at an accelerated temperature and humidity is the
principal quality parameter.
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ISO 18927:2013(E)
−2
IEC 60908 states that the BLER averaged over any 10 s shall be less than 3 × 10 . At the standard (1X)
data rate, the total number of blocks per second entering the C1-decoder is 7 350. Thus, an equivalent
limit on BLER is 220 blocks per second.
A BLER of 220 is an arbitrary level chosen as a predictor of the onset of uncorrectable errors and thereby
end-of-life. A BLER of 220 corresponds to an upper limit for error correction. As a result, lower BLER
discs are recommended to use for long-term storage.
5.3 Test equipment
5.3.1 General requirements
A compact disc player that conforms to ISO/IEC 10149 and software capable of producing a display of
max BLER.
If it becomes necessary to replace the test equipment, the US National Bureau of Standards Handbook 91
shall be followed for correlating test equipment outputs.
The make, model, and version of the test equipment (including software) shall be reported with the
test results.
5.3.2 Calibration and repeatability
Calibration according to the tester manufacturer’s procedure shall be performed prior to any
measurement data being collected. A calibration disc shall be available from an accredited source.
In addition to the calibration disc, one control disc shall be maintained at ambient conditions and its max
BLER measured before and after each data collection interval. A control chart shall be maintained for
this control disc.
The mean and standard deviation of the control disc shall be established by collecting at least five
measurements. Should any individual max BLER reading differ from the mean by more than three times
the standard deviation, the problem shall be corrected and all data collected since the last valid control
point shall be re-measured.
5.4 Test specimen
5.4.1 General requirements
A test specimen is any disc that, after recording, meets ISO/IEC 10149 specifications and contains
representative data extending to within 2 mm of the maximum recording diameter.
5.4.2 Specimen selection
All discs shall be nominally identical with regard to substrate groove structure, layer structure, coating
composition, recording capacity, and age prior to test initiation. It is preferred that the CD-R media be
chosen from different lots and production lines in order to be representative of normal process variations.
All discs shall be maintained in the manufacturer’s transportation and storage conditions prior to recording.
The nominal disc capacity shall be reported with the test results.
5.4.3 Recording system
Specimen discs may be recorded in any appropriate recording device. Since the extrapolated lifetime is
a function of the system including the CD-R media, all discs shall be recorded identically to the extent
possible. Similar recording devices shall be used, as well as similar software and recording conditions.
Discs recorded on different physical devices shall be distributed as equally as possible across the test cells.
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ISO 18927:2013(E)
The make and model of the recording device, the linear velocity employed during recording, and the
software used in the recording system shall be reported with the test results.
5.4.4 Ambient recording conditions
Ambient conditions during recording shall be within the following limits:
— temperature: 15 °C to 35 °C;
— relative humidity: 45 % to 75 %.
During recording, the recording system shall be isolated from external vibrations.
5.4.5 Recording method
It is strongly recommended that all discs be recorded using the “disc-at-once” method. If discs are
recorded using the “track-at-once” method, all errors occurring at the gap between tracks shall be
ignored for the purpose of this International Standard. Packet writing (in which several write events
are allowed within a track) shall not be employed.
Independent of the writing method, the specimen discs shall be recorded as a single session and finalized.
6 Accelerated stress test plan
6.1 General
Information properly recorded in a CD-R system of good manufacture should have a life of several years
or even decades. Consequently, it is necessary to conduct accelerated ageing studies in order to develop
a life expectancy estimate. The key is conducting a test plan that will provide the information necessary
to satisfactorily evaluate the particular system.
Many accelerated life test plans follow a rather traditional approach in specimen selection,
experimentation, and data evaluation. These traditional plans share the following characteristics:
a) the total number of specimens is evenly divided amongst all the accelerated stresses;
b) each stress is evaluated at the same time increments;
c) the Arrhenius relationship is used as the acceleration model;
d) the least squares method is used for all regressions;
e) the calculated life expectancy is for the mean or median life rather than for the first few failure percentiles.
On the other hand, optimum test plans have been proposed which differ in significant aspects from
traditional plans. These plans have the following characteristics:
— two and only two acceleration levels for each stress;
— a large number of specimens distributed mostly in the lowest stress levels;
— the need to know the failure distribution, a priori, in order to develop the plan.
The maximum effectiveness of a plan can either be estimated before the test starts or determined after
the results have been obtained. As each CD-R system will have different characteristics, a specific,
detailed optimum plan is impossible to forecast.
This test plan borrows from the optimum plan, the traditional plan, and previous experience with
the systems, test equipment, and accelerated test stresses to put together a compromise test plan.
Modifications of this plan will be required to design the best plan for other applications. The methodology
shall be applicable to all CD-R media assessments.
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ISO 18927:2013(E)
6.2 Stress conditions
6.2.1 Levels
As mentioned in 6.1, an optimum test plan utilizes only two stress levels for each parameter evaluated.
This is because, in an ideal case, the relationship between changes in the parameter investigated and
changes in stress are known. The compromise test plan, documented in this International Standard,
does not make such an assumption; therefore, three different stress levels per parameter shall be used
so that the linearity of the parameter function versus the stress level may be demonstrated.
The test plan shall have the majority of test specimens placed at the lowest stress condition. This
minimizes the estimation error at this condition and results in the best estimate of the degradation rate
at a level close to the usage condition. The greater number of specimens at the lower stress condition
also tends to equalize the number of failures observed by test completion.
6.2.2 Conditions
For implementing the test plan documented in this International Standard, five stress conditions shall be
used. The minimum distribution of specimens among the stress conditions that shall be used is shown in
Table 1. Additional specimens and conditions may be used if desired for improved precision.
Table 1 — Summary of stress conditions
Test stress Intermediate Minimum
Incubation Minimum
Test cell Number of RH equilibrium
a a duration total time
T(inc) RH(inc)
b
number specimens RH(int) duration
h h
°C %
% h
1 80 85 10 500 2 000 31 6
2 80 70 10 500 2 000 31 5
3 80 55 15 500 2 000 31 4
4 70 85 15 750 3 000 33 8
5 60 85 30 1 000 4 000 36 11
a
T(inc) and RH(inc) are the stress incubation temperature and relative humidity.
b
RH(int) is the intermediate relative humidity that at T(inc) supports the same equilibrium moisture absorption in
polycarbonate as that supported at room ambient temperature and relative humidity.
6.2.3 Temperature (T)
The temperature levels chosen for this test plan are based on the following:
— there shall be no change of phase within the test system over the test temperature range; this
restricts the temperature to greater than 0 °C and less than 100 °C;
the temperature shall not be so high that plastic deformation occurs anywhere within the disc structure.
The typical substrate material for CD-R media is polycarbonate (glass transition temperature
approximately 150 °C). The glass transition temperature of other layers may be lower. Experience
with high-temperature testing of CD-R discs indicates that an upper limit of 80 °C is practical for most
applications.
6.2.4 Relative humidity (RH)
Practical experience shows that 85 % RH is the upper limit for control within most accelerated test cells. This
is due to the tendency for condensation to occur on cool sections of the chamber, e.g. observation windows,
cable ports, wiper handles, etc. The droplets may become dislodged and entrained in the circulating air
within the chamber. If these droplets fall on the test specimen, false error signals could be produced.
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ISO 18927:2013(E)
6.2.5 Rate of stress change
The process described in this International Standard requires that discs undergo a transition from the
ambient conditions to stress conditions and back again a number of times during the course of testing.
The transition (or ramp) duration and conditions shall be chosen to allow sufficient equilibration of
absorbed substrate moisture.
Large departures from equilibrium conditions may result in the formation of liquid water droplets
inside the substrate or at its interface with the information-recording layer. Gradients in the water
concentration through the thickness of the substrate shall also be limited. These gradients drive
expansion gradients which can cause significant disc curvature.
In order to minimize the effects of moisture-concentration gradients, the ramp profile outlined in
Table 2 shall be used. The objects of the profile are
to avoid any situation that may cause moisture condensation within the substrate,
— to minimize the time during which substantial moisture gradients exist in the substrate, and
to produce at the end of the profile a disc that is sufficiently equilibrated to proceed directly to
testing without delay.
The profile accomplishes this by varying the moisture content of the disc only at the stress incubation
temperature and allowing sufficient time for equilibration during ramp-down based on the diffusion
coefficient of water in polycarbonate.
Table 2 — Temperature and relative humidity transition (ramp) profile
Temperature Relative humidity
Duration
Process step T RH
h
°C %
a a
Start at T(amb) at RH(amb) —
b c
T, RH ramp to T(inc) to RH(int) 1,5 ± 0,5
b
RH ramp at T(inc) to RH(inc) 1,5 ± 0,5
Incubation at T(inc) at RH(inc) See Table 1
RH ramp at T(inc) to RH(int) 1,5 ± 0,5
Equilibration at T(inc) at RH(int) See Table 1
T, RH ramp to T(amb) to RH(amb) 1,5 ± 0,5
End at T(amb) at RH(amb) —
Transitions should not deviate from a linear change over the chosen duration by more than ± 2 °C and
± 3 % RH. Ramp transitions may be controlled automatically or manually.
a
T(amb) and RH(amb) are room ambient temperature and relative humidity.
b
T(inc) and RH(inc) are the stress incubation temperature and relative humidity.
c
RH(int) is the intermediate relative humidity that at T(inc) supports the same equilibrium moisture absorption in
polycarbonate as that supported at T(amb) and RH(amb) (see Table 1).
Figure 1 graphically portrays the temperature and relative humidity changes that would occur during
one cycle of incubation at 80 °C and 85 % RH, as specified in Tables 1 and 2.
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ISO 18927:2013(E)
Figure 1 — Graph of nominal 80 °C/85 % RH transition (ramp) profile
6.2.6 Independent verification of chamber conditions
A system independent of the chamber control system shall be used to monitor temperature and relative
humidity conditions in the test chamber during the stress test.
6.2.7 Specimen placement
Disc specimens shall be pl
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Imaging materials - Recordable compact disc systems - Method for estimating the life
expectancy based on the effects of temperature and relative humidity
Matériaux pour image - Systèmes de CD enregistrables - Méthode d'estimation de
l'espérance de vie basée sur les effets de la température et de l'humidité relative
Ta slovenski standard je istoveten z: ISO 18927:2013
ICS:
35.220.30 2SWLþQHVKUDQMHYDOQH Optical storage devices
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37.040.99 Drugi standardi v zvezi s Other standards related to
fotografijo photography
SIST ISO 18927:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 18927:2014
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SIST ISO 18927:2014
INTERNATIONAL ISO
STANDARD 18920
Second edition
2011-10-01
Imaging materials — Reflection prints —
Storage practices
Matériaux pour l’image — Tirages par réflexion — Directives pour
l’archivage
Reference number
ISO 18920:2011(E)
©
ISO 2011
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SIST ISO 18927:2014
ISO 18920:2011(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2011
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2011 – All rights reserved
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SIST ISO 18927:2014
ISO 18920:2011(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Enclosures and containers . 3
5 Storage housings . 3
6 Storage rooms . 4
6.1 Medium-term storage rooms . 4
6.2 Extended-term storage rooms . 4
7 Environmental conditions . 4
7.1 Temperature and humidity specifications for storage . 4
7.2 Environmental conditioning requirements . 7
7.3 Air purity . 8
7.4 Light, use, and display . 8
8 Fire-protective storage . 9
9 Print identification, handling and inspection . 9
9.1 Identification . 9
9.2 Handling . 9
9.3 Inspection . 9
Annex A (informative) Humidity during storage . 11
Annex B (informative) Temperature during storage .12
Annex C (informative) Temperature/relative humidity relationship .13
Annex D (informative) Distinction between originals and copies made for active use .14
Annex E (informative) Air-entrained and gaseous impurities .16
Annex F (informative) Fire protection .17
Annex G (informative) Silver and colour image degradation.18
Annex H (informative) Cold storage practices .19
Annex I (informative) Print stability .20
Bibliography .22
© ISO 2011 – All rights reserved iii
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SIST ISO 18927:2014
ISO 18920:2011(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. Each 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 part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18920 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18920:2000), which has been technically revised.
iv © ISO 2011 – All rights reserved
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SIST ISO 18927:2014
ISO 18920:2011(E)
Introduction
This International Standard is one of a series of standards dealing with the physical properties and stability of
imaging materials.
Photographic and other reflection prints, including hard-copy output from digital imaging systems, have
become increasingly important as documentary and pictorial reference material and art for consumers, as well
as in archives, libraries, government, commerce, museums and academia. This has focused attention on the
importance of preserving such materials to ensure their longest possible life.
The stability and useful life of reflection prints (hereafter referred to as prints) depend on their physical and
chemical properties, as well as on the conditions under which they are stored and used. This International
Standard provides recommendations on proper storage conditions and practices.
The important elements affecting the useful life of prints during storage are as follows:
a) relative humidity and temperature of the storage environment;
b) hazards of fire, water and light exposure;
c) fungal growth and other micro-organisms;
d) contact with certain chemicals in solid, liquid or gaseous form;
e) physical damage;
f) proper processing;
g) enclosures and containers in contact with the print material.
The extent to which the relative humidity and temperature of the storage environment, or variations of both,
can be permitted to reach beyond recommended limits without producing adverse effects will depend upon the
duration of exposure, biological conditions conducive to fungal growth and the accessibility of the atmosphere
to the print surfaces.
The term “archival” is no longer used to express longevity or stability in International Standards on imaging
materials since it has been interpreted to have many meanings, ranging from preserving documents “forever”,
which is unattainable, to temporary storage of actively used materials.
This International Standard defines two levels of recommended storage conditions: medium term and extended
term. Medium-term storage conditions can be used to preserve information for a minimum of 10 years. Extended-
term storage conditions can be used when it is desired to preserve information for as long as possible; these
conditions will prolong the life of all prints, even those not optimized for permanence.
The space requirements and costs for establishing and operating the two levels of storage conditions (medium
term and extended term) differ significantly. Furthermore, the ability to maintain specified limits of temperature
and relative humidity for both sets of storage conditions can be limited due to budgetary constraints, energy
considerations, climatic conditions, building construction, etc. However, any deviation from the specified
conditions will reduce the effectiveness of the storage environment. If such deviation is unavoidable, it is
advisable to select the lowest possible storage temperature that can be maintained. In any event, the best
preservation of prints will be attained with extended-term storage conditions.
This International Standard does not address the various strategies to upgrade substandard environments.
However, institutions with substandard environments and restricted budgets can plan for the improvement
of these environments as resources allow by judicious use of air conditioning, dehumidifiers (or humidifiers),
air circulation and filtration. Although practicalities might force compromises, any improvement in poor
conditions will add to the longevity of materials, even if they do not attain the life expectancies possible with
the environments recommended in this International Standard. The subject of basic air conditioning principles,
the various options and associated costs are outside the scope of this International Standard. There are many
references on this subject.
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The storage of traditional paper collections is not within the scope of this International Standard. However,
many archives containing mixed recording media also include such collections. Archivists are encouraged to
review the appropriate standards for those materials specified in ISO 11799 and in the International Standards
listed in Clause 2.
The recommendations of this International Standard for the storage of prints encompass the following:
— storage enclosures, housing and rooms;
— atmospheric and environmental conditions;
— fire protection;
— handling and inspection procedures.
With the exception of fire and associated hazards that are sufficiently common to warrant inclusion of protective
measures, this International Standard does not pertain to means or methods for protecting photographic
reflection prints against natural or man-made catastrophes.
It is understood that the archivist of a multiple media collection might be forced to limit the number of storage
environments that can be provided. This compromise might be based on the value, physical size, quantity or
legal requirements to maximize life expectancy of some collections relative to others. The issues of mixed
media archives and recommendations for their storage are addressed in ISO 18934.
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INTERNATIONAL STANDARD ISO 18920:2011(E)
Imaging materials — Reflection prints — Storage practices
1 Scope
This International Standard specifies dark storage conditions, storage facilities and procedures for the handling
and inspection of reflection prints of all types and sizes.
This International Standard is applicable to prints on the following opaque supports:
a) fibre-base paper;
b) RC (resin coated) paper;
c) pigmented and other types of plastic supports, e.g. polyester, cellulose acetate;
d) fabric, e.g. canvas, linen.
This International Standard is applicable to the following processed black-and-white silver gelatine prints:
1) wet-processed, including those that have been chemically treated to improve the permanence of the
silver image and/or to modify its colour, e.g. with gold, selenium or sulphur formulations;
1)
2) diffusion transfer, e.g. Polaroid and Fuji Photo Film instant prints ;
3) stabilization-processed (which contain the silver image as well as invisible, chemically stabilized
silver halides).
This International Standard is applicable to the following processed multicolour and monochrome colour
photographic prints:
i) chromogenic, washed and stabilized;
ii) silver dye bleach;
iii) dye transfer;
1)
iv) diffusion transfer, e.g. Polaroid and Fuji Photo Film instant prints , peel-apart or integral;
v) pigmented gelatine, e.g. carbon, carbro.
This International Standard is applicable to black-and-white and colour prints made with the following systems:
— thermal dye transfer (commonly referred to as dye sublimation);
— thermal wax transfer;
— electro-photographic;
— dye and pigmented ink jet;
— swellable and porous-coated media supports;
— diazo.
1) Polaroid and Fuji Photo Film instant prints are examples of suitable products available commercially. This information
is given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of these
products.
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Recommendations for storage of photographic films and storage of processed photographic plates are given
in ISO 18911 and ISO 18918 respectively.
This International Standard is applicable to medium-term and extended-term storage conditions, as
defined in Clause 3.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 18902, Imaging materials — Processed imaging materials — Albums, framing and storage materials
ISO 18916, Imaging materials — Processed imaging materials — Photographic activity test for enclosure materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
extended-term storage conditions
storage conditions suitable for the preservation of recorded information which has permanent value
3.2
fire-protective storage
facility designed to protect records against excessive temperatures, water and other fire-fighting agents, and
against steam developed by insulation of safes or caused by the extinguishing of fires and collapsing structures
3.3
fire-resistant vaults
fire-resistant vaults as defined in appropriate national standards and regulations
NOTE See References [9] and [17].
3.4
insulated record containers (Class 150)
insulated record containers (Class 150) as defined in appropriate national standards and regulations
NOTE See References [7] and [12].
3.5
life expectancy
LE
length of time that information is predicted to remain in an acceptable state when placed in a system at
21 °C and 50 % RH
NOTE In the past, the term “archival” was used to define material that could be expected to preserve images forever,
so that such images could be retrieved without significant loss when properly stored. However, as no such material
exists, this is now a deprecated term and is no longer used in International Standards for imaging materials or in systems
specifications.
3.6
medium-term storage conditions
storage conditions suitable for the preservation of recorded information for a minimum of 10 years
3.7
storage container
box or can be used to store prints
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3.8
storage enclosure
any item in close or direct contact with recording material, such as folders, envelopes, sleeves, albums and mats
3.9
storage housing
physical structure supporting materials and their enclosures
NOTE This can consist of drawers, racks, shelves or cabinets.
4 Enclosures and containers
All enclosures and containers used for medium-term and extended-term storage shall meet the requirements
of ISO 18902 and ISO 18916. This includes enclosures and containers that are in either direct or indirect
contact with the prints. Prints may be stored in envelopes or sleeves of paper or plastic, file folders, folding
cartons, boxes and albums, or may be matted. Prints shall be protected from unnecessary use and light
exposure. Prints that are prone to light-induced fading, especially diazo and some colour processes, shall not
be exposed at all.
Generally, prints smaller than 28 cm × 36 cm in size may be stored vertically, but shall be placed between rigid
supports to minimize slumping and curling. Prints 28 cm × 36 cm or larger should be stored horizontally, unless
mounted on rigid supports. Stacks of horizontal prints should be less than 5 cm high to prevent excessive
pressure on prints at the bottom.
Multiple prints, stored within an enclosure or container, shall be oriented with the emulsion sides against back
sides, never emulsion against emulsion.
Suitable plastic enclosure materials are uncoated polyester (polyethylene terephthalate), polystyrene, high-
density polyethylene and polypropylene. Other plastics may be satisfactory, but there has been no extended
experience with such materials. Glassine envelopes and chlorinated, nitrated, or highly plasticized sheeting
shall be avoided. Specifically, cellulose nitrate and polyvinyl chloride are not acceptable. Glassine is not
dimensionally stable when exposed to high relative humidity, although it may meet the other requirements
specified in ISO 18902 and pass the photographic activity test.
Microclimates (sealed enclosures or cabinetry) shall be used where needed in order to maintain the desired
moisture content of the prints where humidity control is inadequate in storage rooms or where cold storage vaults
and units do not have humidity control, and to protect against gaseous and solid atmospheric contaminants.
A variety of sealed vapour-proof housings, containers and cabinetry can provide this protection (as discussed
in Table 1, 7.1.3.2 and Annex H).
The adhesive used for seams and joints shall also meet the requirements of ISO 18902 and ISO 18916. The
filing enclosure shall be constructed so that the seam or joint will be at the edge of the enclosure and not in
contact with the image layer. Photographic-quality gelatine, modified and photographically inert starch, some
acrylic and polyvinyl acetate adhesives and methyl cellulose are suitable adhesives for use with paper.
For maximum life, prints shall be in a clean condition before being placed in storage and shall be inspected
periodically thereafter, as outlined in 9.3.
5 Storage housings
Prints shall be stored in closable storage housings such as drawers or cabinets, in storage cabinets with tightly
fitting doors, or on open shelves when enclosed inside containers. The storage-housing materials shall be
non-combustible, non-corrosive, and chemically inert, e.g. anodized aluminium, stainless steel or steel with
a non-plasticized synthetic resin-powder coating. Wood, pressboard, particle-board, plywood and other such
materials shall be avoided because of their combustible nature and the possibility of their producing active
deteriorating agents as they age.
The finish on the storage housing materials shall be durable and shall not contain substances that can have a
deleterious effect on the stored prints. Finishes containing chlorinated or highly plasticized resins, or solvents
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giving off gas from freshly applied finishes can adversely affect the image and base layers on prints. Paints used
on cabinets may give off peroxides, solvents and other contaminants for up to three months after application.
Cabinets made of stainless steel or anodized aluminium are recommended. Metal housing materials that have
been powder-coated (a layer of resin particles that are applied electro-statically to the surface of the metal and
then fused to the surface using heat without the use of chemical solvents) are also recommended.
When air-conditioned individually, storage housings shall be arranged to permit interior circulation of air to all
shelves and drawers holding print containers, so as to provide uniform humidity conditions. Storage housing
located in rooms conditioned in accordance with 7.1 shall be provided with ventilation openings that permit
access of air to the interior. Such openings shall not interfere with the requirements for fire-protective storage
or water protection.
Different types of prints, films and other media may be stored in the same storage room separately from each other.
However, different types of material shall not be stored (interfiled) within the same enclosure or storage container.
6 Storage rooms
6.1 Medium-term storage rooms
Rooms and areas used for print storage should be located in the same area as rooms containing provisions for
inspection and viewing of prints. Good housekeeping is essential. Walls and enclosed air-conditioned spaces
shall be designed to prevent condensation of moisture on interior surfaces and within walls, especially during
periods of low exterior temperatures when the walls may be cooled below the dew point of the air.
Provisions shall be made against damage of prints by fire and by water from floods, leaks and sprinklers, and from
[7][9][12][17]
the steam released from masonry walls during a fire . Storage rooms or vaults should be located above
basement levels where possible. A special storage room separated from the work areas for prints of medium-
term interest generally will not be required, provided the conditions recommended in 7.1.2 are maintained.
6.2 Extended-term storage rooms
For extended-term storage, the requirements of 6.1 shall be met.
In addition, the value of photographic prints kept for long-term purposes makes it advisable to provide a storage
room or vault separate from medium-term storage facilities, temporary storage facilities, offices or work areas.
7 Environmental conditions
7.1 Temperature and humidity specifications for storage
7.1.1 General
See Annexes A, B, C, H and I.
The recommended temperature and relative humidity conditions in Table 1 shall be maintained either within
individual storage housings or within rooms containing such housings.
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Table 1 — Maximum temperature and average relative humidity ranges for storage
a
Medium term storage Extended term storage
Relative Relative
Maximum Maximum
ag
Print process humidity humidity
c
temperature temperature
bd
range range
°C % RH °C % RH
e
Black-and-white silver 25 20 to 50 16 30 to 50
Pigment (carbon, carbro)
Dye imbibition (dye transfer)
Silver dye bleach
Dye/silver diffusion transfer (instant)
Diazo
f
Electro-photographic
f
Thermal dye transfer (dye sublimation) 25 20 to 50 2 30 to 50
Chromogenic dye 5 30 to 40
fh
Ink jet (dye or pigment)
a
The values of Table 1 are the required conditions experienced by the photographic material. When micro-climates (housings or
storage containers) are used that establish internal climate conditions, the environment of the exterior room need not necessarily meet
the Table 1 conditions. See Annex H.
b
As discussed in 7.1.3.3, certain gelatine emulsion photographs can be sensitive to RH levels of less than 30 % and can experience
physical changes that can exacerbate existing deterioration such as flaking, cracking and curl. If these materials are present and
RH above 30 % cannot be maintained, then microclimate storage housings or cabinetry shall be used to protect photographs from
extremes in cycling or prolonged excursions below 30 %. Alternatively, a higher RH set point can be selected, e.g. 35 %, when a 5 %
RH fluctuation within any 24-hour period does not exceed the lower RH limit of 30 %.
c
Cycling of temperature shall not be greater than ± 2 °C over any 24-hour period. Some prints can become brittle at low temperatures
and require careful handling when cold to avoid flexing that could cause cracks and image delamination (refer to 7.1.3.3).
d
Cycling of relative humidity shall not be greater than ±5 % RH over any 24-hour period. However, the relative humidity shall not
exceed 50 % RH. If RH cycling in the room cannot be controlled to this level, then microclimate storage housings or cabinetry shall be
used to protect photographs from extremes in cycling or prolonged excursions to either high or low RH.
e
If there is concern about the possibility of silver image deterioration due to atmospheric pollutants, poor quality enclosures,
and/or excessively high temperature and humidity levels, a post-process chemical conversion treatment can be used to provide added
protection (see ISO 18915).
f
The rates of degradation and the potential for physical problems with extremely low temperature and/or low relative humidity
storage is not well known for rapidly changing technologies such as thermal dye transfer (dye sublimation), thermal wax transfer,
electro-photographic, and the many different ink jet image media (dye, pigment, wax) and base media (porous, swellable, plain paper).
Factors such as chemical sensitivity, humidity fastness, and the stability of base materials may have a greater impact on longevity than
thermal stability and light-fastness.
g
Print life expectancy ratings by process type are not provided in this International Standard. For information on print stability, see
Annex I.
h
Some current ink jet prints, especially those utilizing inks made from stable pigment or optimized dyes printed onto stable
supports as recommended by the manufacturer, may have very good image stability at temperatures warmer (up to 16 °C) than the
recommended cold storage temperatures listed for extended-term storage. Where the identification of the type of ink and base cannot
be determined, or where stable ink jet prints may have been interfiled with less stable materials, the colder temperatures listed shall
be used unless prints can be separated by type for storage at different temperatures. The use of non-permanent paper supports or
papers that are not optimized for the particular ink set can also adversely affect the overall stability of the print, requiring storage at
cold temperatures.
7.1.2 Medium-term storage environment
The maximum temperature for medium-term storage shall be 25 °C. Cycling of temperature shall not be greater
than ±5 °C over any 24-hour period, and the peak temperature shall not exceed 30 °C. Some temperature
fluctuation is permitted as long as the relative humidity stays within the specified limits.
The relative humidity of a medium-term storage environment shall be between 20 % and 50 %. Cycling of
relative humidity shall not be greater than ±10 % over any 24-hour period within the specified range (relative
© ISO 2011 – All rights reserved 5
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