SIST-TS ISO/TS 18344:2018

TECHNICAL ISO/TS
SPECIFICATION 18344
First edition
2016-02-01
Effectiveness of paper deacidification
processes
Efficacité des procédés de désacidification du papier
Reference number
ISO/TS 18344:2016(E)
©
ISO 2016

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ISO/TS 18344:2016(E)

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ISO/TS 18344:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Requirements . 3
5.1 General . 3
5.2 Sampling . 3
5.2.1 Material . 3
5.2.2 Procedure . 4
5.3 Process validation . 4
5.3.1 Frequency of sampling. 4
5.3.2 Sample quantities and preparation of samples . 4
5.3.3 Test methods and minimum requirements . 5
5.4 Routine monitoring . 8
5.4.1 Frequency of sampling and sample quantities . 8
5.4.2 Test methods and minimum requirements . 8
6 Report . 8
Annex A (informative) Negative side effects and insufficient deacidification .10
Annex B (informative) Sample forms for documentation .11
Bibliography .17
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ISO/TS 18344:2016(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 46, Information and documentation,
Subcommittee SC 10, Requirements for document storage and conditions for preservation.
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ISO/TS 18344:2016(E)

Introduction
Archives, libraries and similar institutions store written and printed documents which they are
obliged to retain on a permanent basis for cultural reasons and, in some cases, in order to meet legal
requirements.
Often, the condition of these documents is endangered for a number of reasons. One of these is related
to the manufacturing process used for more modern types of paper.
In the industrial age, paper-making processes underwent significant changes. One of the processes
affected was sizing, which, in industrial processes, was achieved by mixing additives into the fibre
suspension before shaping the sheets. These additives included acidic substances like aluminium
sulfate. The reaction of the sizing agent eventually leads to formation of free acids. The acids act as a
catalyst for the hydrolysis of cellulose, making the material brittle. Climatic influences aggravate this
process, air pollution and cellulose degradation processes are a further source of acid in paper.
Another factor for paper stability is the raw material itself. For centuries, paper was made of textile
fibres like linen, hemp or cotton rags which rather deliver stable, long-chain cellulose. The search for a
more abundant raw material led to the invention to produce pulp out of wood by a grinding process. The
resulting ground wood paper still contains most of the lignin and hemicelluloses, in addition to cellulose.
The low pulp purity and the mechanical process causing a partial cutting of fibres lead to a much weaker
paper. Compared to the older rag papers, ground wood paper is also less stable on the long run.
The problem of paper degradation due to acid has developed into a tremendous problem for archives
and libraries. In addition to the processes for deacidifying single sheets, such processes having been
used in conservation for a long time, the past few decades have seen new developments in technical
processes which can be used on a large scale to retard the further decay of cultural assets as bound
volumes and single sheets (“mass deacidification”).
The aim of deacidification is to appreciably improve the life expectancy of paper. This is achieved by
adding an alkaline substance to neutralize existing acid and slow down future acidic degradation for
at least some time (buffering, alkaline reserve). Deacidification cannot improve the actual physical
properties of the paper, but in combination with proper storage, it can slow down further decay.
Without validated analytical methods, it is not possible to assess whether a paper has been deacidified,
or to what degree deacidification has been successful. This Technical Specification compiles the suitable
measurements.
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TECHNICAL SPECIFICATION ISO/TS 18344:2016(E)
Effectiveness of paper deacidification processes
1 Scope
This Technical Specification defines test methods and minimum requirements for paper deacidification
processes regarding their effectiveness and consistency.
It is applicable for all large scale processes which offer deacidification of acid documents made of
printed or hand-written paper.
Possible negative side effects of deacidification processes on the treated objects are not the subject of
this Technical Specification. However, some general recommendations for how to cope with these side
effects are given in Annex A.
It is not specified either, which types of paper objects can be treated by large scale deacidification
methods. Whatever currently available deacidification method is used, some objects might be excluded
from treatment to avoid mechanical damage to paper and bindings or other unwanted side effects.
The provider of the deacidification treatment should inform the customer about the limitations of the
chosen method.
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.
ISO 535, Paper and board — Determination of water absorptiveness — Cobb method
ISO 536, Paper and board — Determination of grammage
ISO 776, Pulps — Determination of acid-insoluble ash
ISO 5351:2010, Pulps — Determination of limiting viscosity number in cupri-ethylenediamine (CED) solution
ISO 5626, Paper — Determination of folding endurance
ISO 5630-5:2008, Paper and board — Accelerated ageing — Part 5: Exposure to elevated temperature at
100 degrees C
ISO 6588-1, Paper, board and pulps — Determination of pH of aqueous extracts — Part 1: Cold extraction
ISO 9184-1, Paper, board and pulps — Fibre furnish analysis — Part 1: General method
ISO 9184-4, Paper, board and pulps — Fibre furnish analysis — Part 4: Graff “C” staining test
ISO 10716, Paper and board — Determination of alkali reserve
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
accelerated ageing
artificially induced ageing under laboratory condition by increasing temperature and sometimes
changing humidity or exposure to light in order to accelerate chemical reactions in paper like hydrolysis
or oxidation to simulate processes usually occurring under natural condition but at a much slower speed
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ISO/TS 18344:2016(E)

3.2
alkaline reserve
compound like calcium or magnesium carbonate neutralizing acids in paper
3.3
average degree of polymerisation
average number of anhydroglucose units (monomers of cellulose) in the cellulose macromolecule
3.4
batch process
deacidification process for a definite quantity of documents
3.5
continuous process
deacidification process for an indefinite quantity of documents
3.6
deacidification
neutralization of the organic and inorganic acids in the paper and deposit of an alkaline reserve as
buffer against any subsequent acidic activity on paper
3.7
extract pH
value obtained in a water extract after the paper has been extracted under defined condition.
Note 1 to entry: Value measured with a glass electrode immersed in a definite quantity of water in which paper
is dispersed in small pieces.
3.8
folding endurance
common logarithm of the number of double folds required to cause rupture in a strip of paper
3.9
mass deacidification
process of paper deacidification on a large scale
3.10
process validation
securing an operation according to preset parameters determined at processed objects
3.11
routine monitoring
monitoring carried out at regular intervals during normal operations
3.12
side effects
any unintended consequence caused by the execution of a treatment process
3.13
test paper
paper with characteristics defined in this Technical Specification, which is deacidified together with
original documents and then analysed
3.14
uniformity of deacidification
homogeneous distribution of the alkaline reserve and pH across the entire sheet and within whole book
blocks
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4 Principle
Specified uniform test papers are treated together with customer’s documents in a deacidification
process. Afterwards, the test papers are examined using standardized test methods. The test papers
are acidic and similar in their properties to common paper qualities produced in the period from
around 1870 onwards. The usage of such papers ensures reliable results and allows comparing different
batches, deacidification methods and treatment plants.
NOTE It is to be emphasized that successful tests according to this Technical Specification cannot guarantee
that all documents treated in the process are deacidified to the same degree as the test papers. The result of a
deacidification treatment strongly depends on the properties of the treated object, such as porosity, thickness,
sizing, coating and acidity of the paper, etc. Therefore, it is impossible to guarantee that certain pH levels and
alkaline reserve amounts are achieved in each object by the deacidification treatment. A passing of the tests
means, however, that there is a high percentage of successfully treated objects.
5 Requirements
5.1 General
This Technical Specification defines test methods for “process validation” (initial testing) and “routine
monitoring”. Process validation is used to prove that a technique fulfils its defined purpose. Routine
monitoring is used to check that the effectiveness determined by process validation is being achieved in
the course of the actual work. Routine monitoring, therefore, is based on process validation.
For “process validation”, extended test procedures should be carried out before and after accelerated
ageing of the samples, including measurements of pH value, alkaline reserve, uniformity of
deacidification and degree of polymerisation.
For “routine monitoring”, alkaline reserve of the test papers is examined.
5.2 Sampling
5.2.1 Material
Both process validation and routine monitoring are performed using samples of test paper, some of
which are deliberately not subjected to the deacidification process serving as a reference.
Table 1 — Test paper
Test paper According to ISO standard
(ground wood-free)
Fibrous material Fully bleached sulphite pulp with hemicelluloses ISO 9184-1, ISO 9184-4
Kaolin filler 12 %–15 % kaolin ISO 776
2
Grammage 80 g/m ISO 536
Surface finish none none
2
Sizing approximately Cobb 60’ 20 g/m ISO 535
Type of sizing Alum rosin sizing Al (SO ) none
2 4 3
Surface sizing none none
Extract pH approximately 5 ISO 6588-1
Optical brighteners none none
a
Acidity, given as negative approximately −0,3 % MgCO
3
alkaline reserve
a
Since no ISO standard is available, the German technical specification Zellcheming ZM IV/58/80 “Prüfung von Papier,
Karton und Pappe…” can be applied. See Reference [2].
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5.2.2 Procedure
All samples should be examined within four weeks after treatment has been completed (including post
treatment measures).
Before the paper is examined, any loose residues occurring as a side effect of the deacidification process
should be removed by brushing.
5.3 Process validation
5.3.1 Frequency of sampling
A complete process validation is required every four years and, additionally, following
— changes to the process technology,
— changes of chemical components or their supplier, or
— changes of the test paper for routine monitoring.
The process validation is valid for all treatment devices of a production site that use the same process
and technology.
5.3.2 Sample quantities and preparation of samples
The process validation is performed using identical test papers (i.e. same production batch). A quantity
of 32 (+4, if folding endurance is included) test sheets, size A5 or larger, is needed for the necessary
testing (see Table 2) of one treated sample set. Four treated sample sets are necessary for the process
validation. The untreated sample set included, the sum of test sheets for one complete process validation
is therefore 148 (+20, if folding endurance is included).
Table 2 — Tested qualities and numbers of test sheets needed
untreated test paper treated test paper
Tested quality (one untreated sample set) (one treated sample set)
unaged aged unaged aged
pH value
4 4 4 4
(cold extraction)
Alkaline reserve 4 4 4 4
Uniformity of deacidi-
12 —
fication
Cellulose DP 2 2 2 2
Folding endurance (op-
(2) (2) (2) (2)
tional)
For batch processes, the test papers should be placed into bound volumes which are thicker than 3 cm
and feature a size of at least A5. For the first sample set, 32 (+4) test papers are placed evenly throughout
the bound volume starting from page number 10.
The test papers should be centred vertically and placed as close to the spine as possible. The test papers
should not extend outside the book block. The second sample set is prepared the same way, but placed
in a different position in the treatment chamber. The third and fourth sample set should be treated on
another day, and if applicable, in another treatment device. The positions of the samples in the chamber
should be documented adequately.
NOTE Service providers can supply a constructional drawing of the deacidification device with the report
and mark the positions of the books containing the test papers.
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For continuous processes, the test papers of one sample set should be treated alternating with sheets of
original items. After further treatment of 100 sheets of original items, the second sample set should be
treated to the same pattern as the first. The third and fourth sample sets should be treated according to
the first two sample sets, but on a different day, and, if applicable, in another device.
5.3.3 Test methods and minimum requirements
5.3.3.1 Accelerated ageing
Perform accelerated ageing of 10 (+2) test sheets of each of the four sample sets and 10 (+2) untreated
test sheets as described in ISO 5630-5:2008, Clause 4 to 9.2.
Test tubes selected for this study shall be perfectly gas-tight and large enough to accommodate paper
strips pre-cut for further measurements. It is required to perform aging for all samples simultaneously,
in the same laboratory oven, using one type of a glass tube for all samples.
NOTE To ensure perfect airtightness of testing tubes, the following steps could be taken:
— original tube caps supplied with glass tubes could be exchanged for caps made of material with higher
resistance to mechanical and thermal stresses (e.g. polyphenylsiloxane);
— sealing material – PTFE or silicone gaskets and o-rings should be avoided, fluoroelastomers are advisable
(e.g. Viton);
— tightening of the tube with the use of the dynamometric wrench equipped with a tube cap holder, to ensure
good repeatability of obtained sealing.
5.3.3.2 pH value
The pH value has to be measured in an aqueous extract as described in ISO 6588-1.
The average results and the average and the relative standard deviations should be given for treated
paper with and without ageing, and the results should be expressed to two significant digits.
The measured pH of the paper following deacidification has to be higher than 6,5 (before accelerated
ageing).
NOTE 1 The pH value of an aged sample will normally be lower compared to those of the non-aged sample. For
a given paper, ageing after deacidification should only lead to a small reduction of its pH value. It is possible that
the pH value measured after accelerated ageing will level out at around 6,5, even though an alkaline reserve is
still present. This is particularly true of the pH value on the paper surface which is usually one unit lower than
the pH value of the cold extract. Under these conditions, however, this kind of paper can still be described as
being neutral.
The pH value discussed here applies solely to the described test papers. If original papers are examined
as well, special agreements on an acceptable final pH value should be reached with the customer, as the
achieved pH value depends very much on the original composition of the paper.
NOTE 2 In addition to this measurement of aqueous extract pH value, measurements of surface pH value are
sometimes performed. The surface pH measurement is a faster method compared to extraction pH measurement
to judge the pH value of a paper. If applied correctly (see Reference [3]), surface pH measurements also allow on-
site measurements of original books and documents in libraries and archives and can also be used to follow the
stability of deacidification on a longer timescale. However, surface pH measurement has its limits. It works well
for acidic to neutral papers and also gives reasonable data until about pH 9. Usually, surface pH measurement has
been successfully used with immersion treatments. Surface pH measurement may fail to give reliable results when
larger amounts of alkaline reserve deposits are present at the paper surface and the solubility limit is reached.
5.3.3.3 Alkaline reserve
Determine the quantity of alkaline reserve of each of the four sample sets as described in ISO 10716.
For determination of the dry matter content, it is in deviation to ISO 10716 sufficient for the purpose of
this Technical Specification to weigh about 1 g to the nearest 0,001 g.
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The results, the average and the relative standard deviation should be given for treated paper with and
without ageing, and the results should be expressed to two significant digits.
The minimum alkaline reserve is 0,5 mass % expressed as MgCO .
3
NOTE Part of the total amount of alkaline substance applied to the paper by deacidification treatment is
chemically converted (“consumed”) by the neutralization reaction, and the remainder is the “alkaline reserve”.
The alkaline reserve ensures that the paper is resistant to acids acting upon it due to environmental influences
or degradation reactions occurring after the deacidification process.
5.3.3.4 Uniformity of deacidification
The uniformity of deacidification is measured by quantitative determination of the alkaline reserve,
expressed as mass % MgCO , at six different segments of a treated sample. Figure 1 shows the cutting
3
pattern for the segments.
Figure 1 — Segments for the determination of alkaline reserve for uniformity test
As one A5 sheet of test paper is not sufficient for analysing uniformity due to the limited sample
amount (for alkaline reserve 1 g of sample is required per data point), the measurement of the alkaline
reserve of the six treated paper samples is carried out as described in ISO 10716, with the following
amendments: Three A5 test paper sheets are cut into six rectangular, numbered segments of equal size
according to the pattern shown in Figure 1. Then, the three pieces with same numbers are put together,
divided into small pieces as described in ISO 10716, and the resulting pile is mixed well. About 1 g of
pieces is weighed and treated as described in ISO 10716.
Alkaline reserve measured for each section should be not less than 0,5 % by weight calculated as
MgCO equivalent. In addition, the relative standard deviation of the six individual measured values is
3
required to be less than 30 %. The lower the deviation calculated in this way, the better the uniformity
of deacidification.
NOTE 1 The results of these measurements describe the distribution of the added alkaline substance over the
entire surface area of the sheet of paper, not its homogeneous distribution across its thickness/cross section. For
the latter, no standardized routine methods are available.
NOTE 2 Some alternative methods exist which are able to address the uptake of deacidification reagent, in
most cases, the concentration of cations is analysed. However, these methods do not suffice as a full displacement
of alkaline reserve determination, as most of them are not fully comparable with the actual amount of alkaline
reserve. However, to estimate whether mass deacidification was homogeneous they can serve as alternative.
Potential methods are based on inductively coupled plasma optical spectrometry (ICP/OES) after the alkaline
reserve was extracted by acid from the paper segments, X-ray-Fluorescence scanning or FTIR/NIR and other
methods which reliably report the uptake of deacidification reagent.
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5.3.3.5 Degree of polymerisation
A pretreatment to remove the excess of alkaline reserve in the sample has to be performed as follows:
Disintegrate 1 g to 3 g of paper sample in a mixer for less than 30 s directly in 1,5 L, 0,1 M HCl at room
temperature (for 3 g of paper sample with 2 % alkaline reserve this corresponds to >200 fold excess of
acid when 1,5L are used). Rinse the sample thoroughly with water until washing water is neutral. Dry
sample at room conditions according to ISO 5351:2010, Clause 8. The sample preparation should be
adapted to the ingredients of the deacidification process.
NOTE 1 ISO 5351:2010, Clause 8 requires 10 g of material, but 1 g is sufficient for the DP sample preparation in
the present case.
Determine the degree of polymerisation by measuring the viscosity average with CED as described
in ISO 5351 before and after accelerated ageing. For determination of the dry matter content, it is in
deviation to ISO 5351 sufficient for the purpose of this Technical Specification to weigh about 1 g to the
nearest 0,001 g. The average results of the limiting viscosity number should be given for treated and
untreated papers with and without ageing, and the results should be expressed in millilitres per gram.
After accelerated ageing, the limiting viscosity number of the treated paper has to be higher than that
of the untreated paper.
NOTE 2 When looking at different deacidification treatments, the ratios of the limiting viscosity numbers of
treated versus untreated papers after ageing can be compared if identical test papers are used.
For the calculation of DP, a [η]-DP relation for cellulose dissolved in CED is given in the formula below.
0,9
The limiting viscosity number is converted to degree of polymerisation by DP = √(1,65 × [η]) (see
Reference [5]).
NOTE 3 The degree of polymerisation describes the average chain length of a polymer, in case of paper that
of the mixture of cellulose and hemicelluloses. As the stability of paper is directly related to the chain lengths
of (hemi) cellulose (longer polymer chains usually give stronger papers) this parameter can be considered as
very important for the entire integrity of paper. In addition, it is a sensitive measure of cellulose degradation and
hence very useful to address changes upon aging before and after deacidification. The sample amount required
for analysis ranges between 75 mg and 750 mg for a triple deter
...