An Investigation of Some Environmental Factors Affecting Migration-induced Degradation in
Paper
by JOHN SLAVIN & JIM HANLAN
MIGRATION-INDUCED DEGRADATION
Degradation believed to be the consequence of the migration of impurities
from one cellulose-based material to another has several characteristic features evident upon
inspection of a paper artifact. Discoloration is the most salienr feature. It often appears dark with a
yellow-brown colour that contrasts with the areas of the paper object unaffected. If localized, the
discoloured area, conforms in size, shape, or contour to that of the source material it was in contact
wish. The pH of the discoloured area is usually lower than that of unaffected areas.
The most common examples of this are framed works on paper where the window mat or hacking
board have substantial impurities, and books in which the text block is in contact with covering
materials with impurities. In a study of book paper deterioration, Barrow was the first researcher to
attribute the discoloration, decrease in fold endurance and decrease in pH of the text leaves in two
books to the migration of impurities.1
Degradation due to migration is difficult to detect when it is not initiated by contact. It may well be
that migration abo occurs with the diffusion and subsequent absorption of volatiles within an
enclosed space by objects not in contact and perhaps not even in close proximity. For instance,
migration via atmospheric diffusion might occur in library and archive storage areas where poor air
circulation may lead to high concentrations of volatile degradative agents evolving from large
quantities of deteriorated records or books. Kahle reported a case of the mass acidic deterioration of
book papers in storage apparently due to an aerial migration process.2 This phenomenon is difficult
to isolate from the degradative processes initiated by atmospheric pollutants (such as oxides of
sulphur and nitrogen or such participates as dust) or by reactions brought about by heat, light and
moisture.
The most common source of migrating impurities is inferior-grade wood pulp papers, boards and
cardstock. They are classified as inferior because of
their high content of noncellulosic matter. A typical ground wood pulp paper contains less than 50%
cellulose. Hemicelluloses, lignin, small amounts of minerals and extraneous substances (mainly
low-molecular-weight extractives) are also present.3 The rate of deterioration of these papers is
accelerated by the presence of these impurities as well as by decreasing cellulose crystallinity
(vulnerability to attack) and the presence of degraded cellulose. The high concentrations and range
of decomposition products increase the potential for migration. Identifying the products that could
migrate is extremely difficult. Such products have certain properties, however, that could be
expected to create conditions for migration. For example, molecules or ions that are relatively small
and have a low molecular weight arc likely to be volatile, which can be conducive to diffusion
through a paper substrate. Molecules and ions of sufficient volatility can diffuse under a chemical
potential gradient. Flow can be brought about by a pressure gradient4; in the case of a paper
substrate, this would be osmotic. Moisture content and temperature could be critical factors in either
case.
The common belief in the conservation field is that the degradation products that migrate are acidic.
Cunha states that "acid in paper, like acid in ink, migrates to the paper, cardboard, textiles or leather
in contact with the contaminated sheets."'' Acid migration is the term most often used in the
literature. Very small amounts of moisture can give rise to the formation of acids, which cause
cellulose to degrade by hydrolytic reactions. The higher the acidity (hydrogen ion concentration),
the faster the degradation.
Wood pulp papers can degrade much quicker than cotton pulp papers.6 This can be attributed, in
part, to the hydrolysis of hemicelluloscs during sulphite cooking to form aldonic or sulfonic acids.
Organic acids (i.e., uronic) arise from the cleavage of acetyl groups and possibly through the
oxidized products derived from the methoxy groups found in hemicelluloscs.7 Hemiccllu-loses arc
more sensitive to hydrolysis than cellulose, since they are branched and amorphous and are
composed of smaller sugar units with weaker glycosidic bonds. Another reason wood pulp paper
hydrolyses more rapidily than cotton-based paper is the presence of aldehydes at the C-6 cellulose
atom introduced during pulping.7 Lignin also contributes to the acidity producing carboxylic and
sulphonic acids.
Although acid migration is known to take place with other materials (i.e., sulphuric acid from iron
gall ink and acetic and formic acids from wood), migration in paper has not been characterized.
Both Barrow1 and Daniels8 have cited cases in which migratory degradation has occurred, yet the
pH of the initiating or source material was higher than the pH of the discoloured material when
comparisons were made across regions of contact. This indicates
that the reaction did not likely entail the transfer of acidic constituents from the source material.
Oxidative degradation plays a key role in the deterioration and discoloration of paper and may be
integral to the initiation of migratory degradation. Oxidized cellulose has a large number of
carbonyl and carboxy] groups, and the presence of peroxides in aged pulps indicates that
atmospheric oxygen is involved in the process. In the absence of oxygen, deterioration is slowed
significantly. Arney & Jacobs9 found that the rates of yellowing of both newsprint and cotton rag
paper varied linearly with oxygen concentration and were accelerated by moisture.
Tt is possible that the degradation phenomenon referred to as acid burn or air burn could be the
result of the deposition of volatile degradation products on a paper substrate adjacent to the source
material. The resulting discoloration might then be catalysed by surface exposure to oxygen and
moisture present in the air. These reactions arc most intense in the immediate vicinity of the source
material. Oxidizing agents such as peroxides could be involved.10 Hydrogen peroxide is liberated
during the oxidation of lignin.11 Free radical initiators, like peroxides, arc very reactive and arc
oxidation products. Both arc capable of diffusing through layers of paper find may be capable of
initiating oxidative reactions in other paper objects in close proximity.12 Daniels8 cites several cases
of discoloration thai occurred as a result of a reaction between two or more materials on close
contact over a long period of time. By forming Russell-effect images on a modified photographic
film, concentration levels of peroxides were recorded from the deteriorated papers being examined.
In several different cases, the concentration of peroxides was higher where there was discoloration
than in areas not discoloured. These findings indicate that degradation resulting from migration may
often be due to an induced oxidation reaction.8
In addition to the organic acids and oxidation products mentioned, the presence of phenols (in
lignin) as well as furan and pyrone derivatives indicates that, under the influence of high
temperatures and possibly with the aid of other decomposition products acting as catalysts, aliphatic
chains arc transformed into ring-structured aromatic compounds that could play a part in migration
reactions.13
Evidence of the production of volatiles from paper is limited. Desai & Shields14 suggested that
weight losses in the photochemical degradation of paper they tested occurred because of the loss of
volatilcs. Differences in the graph of percentage weight loss vs decreasing degree of polymerization
indicated that volatile matter may have been the result of secondary degradation reactions.
However, the study was inconclusive.
PRESERVATION M EASURES
Degradation involving volatile products from paper and other cellulosic materials has been used to
account for the phenomenon of sealed materials aging more rapidly than unsealed materials. Library
of Congress studies reported thai encapsulated papers age at a faster rate due to an autocatalytic
reaction. They define this as "the speeding up of degradation by the presence of volatile degradation
products, trapped and concentrated within the enclosure".15 They also found that heat affects this
reaction. As a result of this study, it was recommended that air gaps be left in enclosures to diffuse
these volaliles. Two years later in a follow-up study, Shahani16 reported that these gaps did not slow
down the faster rate of deterioration of encapsulated papers.
Without further evidence of both the identity and mechanism for volatile emissions from degraded
papers, preventive conservation is difficult. The use of buffered papers with acidic objects has often
been advocated in conservation literature. Clapp17 and Barrow1 stated that a neutralization reaction
occurs between buffered and acidic, papers. Clapp'7 recommends that, "if a valuable paper is acid,
placing it against a, buffered back paper may help retard injury by absorbing random acidity and
neutralizing the housing'''. Barrow' made this same claim. Research to date has been inconclusive
with conflicting results. Shahani16 reported that, although neutral paper encapsulated with a
buffered sheet ages at the same rate as one not in contact with a buffered sheet, acidic paper did
benefit from encapsulation with an alkaline sheet. However, research by Santucci18 showed that an
alkaline reserve could only be effective in slowing the rate of degradation at a high relative
humidity (70% or higher). Since neutralization reactions require a certain volume of water to
proceed, the effectiveness of buffered papers in normal storage conditions is questionable. Daniels8
recently advocated low relative humidity storage for inhibiting migratory degradation. Barrow1
emphasized low storage temperatures. These are effective measures to take in dealing with cellulose
deterioration but the direct effect of environmental conditions on aerial or contact migration
reactions has not been studied.
EXPERIMENTAL - PART 1 Outline
The purpose of this part of the study is to provide evidence of any influence selected environmental
factors may have on migratory degradation. We exam-
ined the effects of heat, humidity and exposure on the acidity of neutral paper specimens in
environments containing degraded newsprint. Sample sets were prepared, conditioned and placed in
sealed chambers. The pH of each specimen in a sample set was measured after aging and compared
with that of controls.
Sample specimens
Each specimen consisted of a neutral strip of unsized paper (Whatman no. 1 filter paper, 100%
cotton cellulose) in uniform contact with a strip of acidic newsprint (wood pulp with lignin, dated
1913). Both had the same dimensions, which were calculated from Whatman strips weighing 0.05
±0.01 g. The dimensions were 3.5 cm x 13.5 cm. Some specimens had a buffered or unbuffered
tissue interleaf (weighing 0.29 g and 0.11 g respectively) between the newsprint and Whatman
papers.
Whatman filter paper was chosen as the receptor paper because of its purity, absorbency and
uniform surface. It had an initial pH of 6.7. Degraded newsprint was selected as the potential
initiator of any migratory contaminants because it consists of softwood-sulphite and ground wood
pulp (based on the date), which produces a wide range of degradation products in relatively large
concentrations afler 70 years of aging. This was evident upon inspection. The paper was brownishyellow and extremely friable. It had a pH of 3.9, which was desirable, since a very low pH initiator
sheet might enhance the rate or degree of any migration of degradation products. Newsprint is often
stored in large quantities in archives and libraries, where volatile degradation products can
accumulate.
Interleaving tissues were studied since they are widely used in conservation for protective storage of
textiles and works on paper. In instances in which acidic objects must be stored, buffered tissues arc
commonly believed to inhibit acid migration. For this study, Archivart tissue was selected (flax
fibre content with a 25% CaCO3 buffer producing a pH of 8.7). It is purported by the supplier to
offer protection against acid migration. An unbuffered tissue with a pH of 6.2 was also selected for
comparative purposes.
Sample sets
Each sample set consisted of 12 specimens: four had a newsprint and a Whatman sheet in contact,
four had an interleaf of buffered tissue between Whatman and newsprint and four had an interleaf of
neutral tissue. Of the four sample sets prepared, one wras encapsulated in 0.13-mm Mylar, one
exposed on both
sides to the ambient conditions of the chamber, and the last two sets were exposed on one side and
sealed on the other (one set with the initiator side exposed and the other set with the receptor side
exposed). The exposed specimens were placed between reemay (100% spun polyester that is very
permeable) and held in contact between two pieces of rigid polystyrene grating. This plastic grating
consists of a grid of square cells 1 cm across. It ensures uniform contact between specimen sheets
over the entire area of the. specimen and, at the same time, does not prevent surface exposure to the
air. Sample sets exposed on one side only were scaled on the other side with 0.13-nun Mylar
supported by a piece of four-ply museum board. These sets were also sandwiched in contact
between sheets of the plastic grating. Encapsulated specimens were laid out on a sheet of grating. In
addition to these four sample sets were two sets of controls consisting of isolated sheets of
Whatman paper -one set exposed and the other encapsulated.
Prior to sample preparations, the newsprint, tissue and Whatman filter paper were cut to size and
pre-conditioned for 24 h at the desired relative humidity (RH) level at room temperature. The
newsprint was isolated from the tissue and filter paper in another chamber, since volatile
degradation products might be present.
Environmental conditions
The four sample sets and two controls were suspended one above the other, with adequate spacing
for air circulation, inside sealed chambers; each containing a saturated salt solution to control
humidity. Five chambers were used to investigate the effect of temperature and RH on any
migration that might occur. Each chamber consisted of a rigid box framework of angled aluminium
sealed inside and out with polyethylene. Conditions in the chambers were:
1. 23°C and 82% RH - potassium bromide salt solution
2. 23°G and 52% RH - sodium sulphate salt solution
3. 23°G and 33% RH - calcium chloride salt solution
4. 40°C and 78% RH - potassium bromide salt solution
5. 40°C and 27% RH - magnesium chloride salt solution
Two ovens were, used to maintain the higher temperature for chambers 4 and 5. All chamber's were
kept in the dark to control for light exposure. Samples were left in the chambers for five weeks.
Analysis - pH cold extraction
After the samples were removed from the chambers, cold extraction pH measurements were taken
of all Whatman sheets, interleaving tissues and selected newsprint sheets. The method followed for
extraction and measurement was that outlined by TAPPI (T-509 os-77). Double-distilled, deionized
water was used. One exception to the TAPPI guidelines was the weight of the test specimens. Due
to constraints in the volume of the ovens used and the large number of specimens in each chamber,
(he size and weight of the specimens were smaller than recommended, but this does not affect the
accuracy of the measurement if great care is taken to avoid contamination of the specimens during
handling. Since the newsprint and interleaf sheets were the same dimensions as the Whatman sheet,
the weights varied and the volume of water used for extraction therefore varied as well.
Macerated specimens were left for 1 h in glass beakers sealed with Parafilm. Final readings were
taken with a flat surface, gel-filled pH electrode. A minimum of three readings were taken of three
identical specimens in each specimen group. When there was a discrepancy between the highest and
lowest of the three readings equal to or greater than 0.5 of a pH unit, a fourth reading was taken.
Results
Temperature and relative humidity
The overall effect of temperature and RH on the combined sample sets of each chamber was
examined by comparing pH means.* (Note that all references to pH readings refer to Whatman
sheets unless otherwise stated.) Chambers ) and 5 had a temperature almost twice as high as
chambers 2 and 4. By comparing samples from chambers where the RH is similar, we found that
the higher temperature causes a greater decrease in pH. Where temperature is constant and the RH
varies, high RH causes a greater decline in pH (Table 1, A pH). The results indicate that both
increasing temperature and increasing RH accelerate pH decline. Since this relationship is
characteristic of paper aging, the portion of the pH change that is induced by migration is selected
out in Table 2 by doing control comparisons.
First of all, RH had a dramatic effect on the control sample set (Table 2a).
* Cold extraction pH readings were recorded io within 0.05 units and calculations of means
are reported to within 0.] pH units as stipulated by TAPPI. All subsequent calculations were
checked for statistical significance.
High RH caused greater acidic degradation in the exposed controls. At 40°G and 78% RH (#1), the
disparity between exposed and encapsulated papers was —1.2 pH units. When the RH was 27% at
the same temperature (#5), the difference was only —0.5. The same was true at 23°C, At 82% RH
(#2) the difference was -1.1 and at 33% (#4) it was -0.3.
The greater decline in pH of the exposed control specimens may he accounted for by the presence
of volatile degradation products from the newsprint in each of the chambers. The influence of RH
suggests that a form of aerial migration could be taking place In which water vapour plays an
important role in transporting and/or reacting with volatiles to catalyse acidic degradation. If this
were the case, the Mylar would be protecting encapsulated paper specimens by preventing the
deposition of volatiles - even though Mylar is not a completely impermeable material.
Since the encapsulated controls were not affected by migrating impurities, they were compared with
the other sample sets to distinguish the portion of the change in pH due to migration (Table 2b). All
specimens in the other sample sets decreased in pH as a result of a migration process. Specimens in
chambers where either the temperature and/or the RH were high had the lowest p?I means. With the
exception of the specimens that had a buffered tissue interleaf, the greatest migration-induced
decline in pH occurred in chamber 1, where both temperature and RH were high.
Exposure
Further analysis of the different sample sets confirms that the Mylar enclosures do not transmit
volatile degradative by-products. The pH means of exposed sample sets were compared with
encapsulated sets and partially exposed sample sets. Data from all chambers were combined to
exclude the variables temperature and RH from the final analysis (Table 3). The Whatman paper
from the encapsulated sample sets decreased in pH to the same degree as the exposed
Table 2a. Migration-induced changes in pH
W & N denotes a specimen consisting of a piece of Whatman paper in contact with a piece of
newsprint of identical size — except where an interleaving tissue was inserted between the two. The
change in pH was calculated by subtracting the pH mean of the encapsulated controls of a given
chamber, from the pH mean of the sample set indicated from the same chamber. The encapsulated
Whatman control was selected because it was not subjected to newsprint volatiles (see Tables 2a
and 3).
controls and exposed sets. Volatiles from the newsprint built up to high concentrations within the
Mylar enclosure and accelerated degradation of the Whatman sheets contained with it, resulting in a
decline of 0.6 in pH. Partially exposed specimens (with the initiator side exposed and the receptor
side sealed) did not decline in pH to the same extent as the fully exposed specimens.
This suggests that air flow and likely the presence of oxygen may play a key role in the transport
and/or reactivity of such volatiles as peroxides.
Table 4 isolates the portion of the pH decline of specimens due exclusively to physical contact with
the acidic newsprint. This was calculated by subtracting the mean pH change of the exposed
controls from the total mean pH change of specimens in the set in which Whatman was in contact
with newsprint. In no instance was there any statistically significant pH decline due strictly to
contact with the newsprint.
The above findings confirm that the migration of degradative agents was a
consequence of their volatility and was not influenced by any physical or chemical forces at work
between sheets of paper in contact.
Interleaving
The barrier properties of interleaving tissues were evaluated. Unbuffered and buffered tissues had
little or no effect in retarding migratory degradation in chambers 3, 4 and 5 (Table 5). In chambers 1
and 2, where the RH was high, the buffered tissues were effective at reducing the degree of acidic
degradation. This was the case for both exposed and encapsulated sets (Table 2b). This may be due
to a number of factors, The buffered tissue is physically less permeable than the unbuffered tissue.
Fibre type, fibre density, CaCO3 buffer content or a combination of these factors could be
important. Besides this reduced diffusion capacity of the buffered tissue compared with the
unbuffered
Table 4. Changes in pH resulting from contact-initiated migration
Table 5. Effect of interleaving on the p!I decline of Whatman paper
tissue, the potential of a neutralization reaction occurring at high humidities
also inhibits pH decline. There was no statistically significant drop in pH of the buffered (issue
itself (Table 6). The neutral tissue interleaf had a negligible effect in inhibiting pH decline and the
pH of the tissue decreased more than the buffered tissue in most sets. At normal room temperature
and RH (23°C and 52% RH), there was no difference in the degree of pH change between
specimens with a buffered tissue interleaf, those with an unbuffered tissue interleaf and those with
no interleaf (Table 5).
It should be remembered that this was a short study (5 weeks) and these results cannot be
extrapolated over longer periods of time.
EXPERIMENTAL — PART 2
In an attempt to identify the specific products of degraded newsprint that are volatile, air samples
were collected from environments in which they might be
Table 6. pH decline of interleaving tissue
expected to accumulate. These samples were then analysed for a variety of chemical groups that
could be present by using gas ehromatography.
First sampling for volatiles
The purpose of this sampling was to determine whether identical gas ehromatography peaks
resulting from volatile impurities would be recorded in both an institutional storage area containing
large quantities of degraded paper and in an experimental control consisting of a scaled chamber
containing degraded paper.
The sampling procedure was first carried out in a closed stack area in the Douglas Library at
Queens University, Kingston, Ontario. A very large collection of bound newspapers dating from
1840 to 1960 is housed there within an area of approximately 270 m3 closed off on three sides. The
area is ventilated and lit with warm white fluorescent lights.
Three air samples were taken by inserting two extraction filters and one impingcr into the chamber
through an outlet in a side wall. The (liters and impinger were connected to Gilian high flow
samples which drew in the air. The flow rate was 200 rnl/min and the duration was 1 h. The two
extraction filters and the impingcr contain different matrices for the deposition of specific types of
compounds that may be present in the air drawn through. One filter contained a charcoal matrix for
extracting various organics. Another filter contained silica gel for collecting Cl, NO2, NO3 and SO4
(acid groups). The impingcr contained 0.1 N NaOH with 0.017 μg of hydrogen peroxide. This is
used for detecting phenols.
This sampling procedure was repeated within a scaled chamber containing the same aged newsprint
used in part 1 of this study. Approximately 1600 g of newsprint was shredded and placed on a
polystyrene grating inside a sealed chamber with a volume of 0.43 m3. It was left there in darkness
for three days at 22°C and 55% RH.
Second sampling
A second control sample was collected to isolate the source of any volatiles recorded. The same
sealed chamber used in the first sampling was used. Four charcoal tubes were used. Two were used
for extraction from the sealed chamber without newsprint in it to compare the results with those
from the first sampling. The other two were control samples extracted when the chamber contained
newsprint (same volume as the first sampling). The
newsprint was left in the chamber for three days prior to sampling at 22' C) and 55% RH.
Analysis
Gas chtomatography — just sampling
The charcoal tubes were desorbed with 1 ml of CS2 and run through a UBS capillary column (30 m
long, narrow bore). A flame ionization detector was used. Silica gel tubes were desorbed with 10 ml
of 0.004 Na2CO3 solution run through an ion chromatograph. The impinger solution was acidified
with H2SO4 and run through a GC column of tenax (1.2 m NIOSH method 5330). Flame ionization
detection was again used. Blank tubes were run as references in all three cases.
Second sampling
The charcoal tubes were labelled 1 to 4 with lubes 1 and 2 used on the empty chamber, and tubes 3
and 4 used on the chamber after the newsprint had been left in it for two days. Tubes J and 4 were
desorbed with CS2 (as above) with an oven temperature programme of 40°C for 6 min followed by
a 10°C/ min rise to 200°C, where the temperature was maintained for 3 min. Tubes 2 and 3 were
desorbed with formic acid and run through a packed column of Carbopack B 60/80 mesh and 3%
Carbowax 20 M on 0.5% H3PO4 (1 m glass column, NIOSH method). The oven temperatures were:
100°C for 20 min and I50°C for 30 min.
Results
First sampling
In both the library and chamber samples, no peaks were recorded for: Cl, SO2 or SO3, NO2, N2O4
and phenols. Within the limits of this analysis, these potential volatiles were not present. Some trace
impurity peaks were recorded from the charcoal matrix tubes for both library and chamber air
samples. Since a few of these were of similar retention times in both library and chamber samples, a
second sampling was done to confirm whether these peaks resulted from volatile impurities coming
from the newsprint.
Second sampling
Analysis for acetic and other low-rno!ecular-weight carboxylic acids was negative. No volatiles
were detected in either the empty or full chamber, with the
exception of two peaks that seem to match peaks found in the first sampling in both volume and
retention time. One could not be associated with newsprint, since it was present in samples from the
empty chamber. The other was likely to have been produced by the newsprint, since it is not present
in either the blank or the empty chamber sample. It is an extremely small trace impurity that is
unidentifiable without further sampling and mass spectrometric analysis, which was not available.
Therefore, il cannot be considered conclusive proof of the presence ol specific volatiles from
degraded newsprint.
CONCLUSION
It should be remembered that the acidic degradation of paper, measured by changes in pH, is a
fundamental but far from comprehensive analysis of the condition of any paper object. This study
used comparative pH reading analysis principally because the process has been and is still being
referred to as acid migration. The results from the first part of this study indicate that this form of
degradation can be induced quite readily and that an increase in acidity is one of its most salient
consequences. Unfortunately, the second part of this study failed to identify the volatiles.
The following conclusions summarize the specific results of this study:
• Significant migration-induced degradation can occur within short periods of time, causing
increases in the acidity of affected paper.
• Migration-induced degradation appears to be accelerated by increasing RH and, to a lesser extent,
by increasing temperature. High RH contributed to the transport and deposition of degradative
volatiles present in the chambers.
• Migration-induced degradation is not necessarily a contact-based phenomenon. Neutral pH paper
decreased in pH to the same degree, whether it was in physical contact with the acidic newsprint or
just exposed to the chamber environment where volatiles from the newsprint were present.
• Mylar encapsulation is an effective barrier for volatile degradation products. Although it will
keep external volatiles from penetrating to attack a vulnerable paper object, it will also prevent any
volatiles generated within from escaping and thereby accelerate pH decline.
• If samples were only partially exposed to the contaminated chamber environment there was a
smaller decline in pH relative to fully exposed samples. Air flow, particularly the presence of
oxygen, may play a role in the transport and/or reactivity of volatiles.
• Tissue interleaf buffering was only effective in inhibiting migration-induced changes in pH at
high relative humidities (> 70%). However, the buffering
did inhibit pH decline of the tissue itself. Unbuffered tissues had no significant effect under any
conditions.
• The presence of volatile degradation products was not confirmed by gas
chromatographic analysis of air samples. This was not a conclusive analysis, given the limitations
of the method of sampling and detection (it is most effective at finding specific known impurities).
No previous studies have empirically identified volatiles from degraded paper.
Although environmental factors play a key role in migration-induced degradation, conclusive
findings will be difficult to derive without further analysis and identification of the volatile
degradation products that can be produced by paper.
ACKNOWLEDGEMENTS
We would like to thank Professor Poland at Queen's University for generous help in collecting and
analysing air samples, Helen Burgess at the Canadian Conservation Institute for recommendations
and advice on experimental procedure and Lynn Stewart for assistance in preparing the text. This
research was supported by Queen's University and its Art Conservation Program.
SUMMARIES
An Investigation of Some Environmental Factors Affecting Migration-induced Degradation in
Paper
The influence of selected environmental factors on the degradative process commonly referred to as
acid migration was studied: the effects of heat, humidity and surface exposure on the acidity of
paper specimens in contact with or in close proximity to acidic newsprint. Interleaving tissues and
Mylar encapsulation were studied for their potential barrier properties. The experiments indicated a
significant migration-induced degradation; it was accelerated by increasing temperature and
humidity. Although encapsulation protected specimens from external volatiles, it accelerated the
rate of degradation if internal volatiles were present. Buffered tissue interleaving only inhibited
migration at high relative humidities, whereas unbuffered tissue was ineffective in all cases.
Recherche sur Quelques Facteurs Environnementaux Influencant la Degradation du Papier par
Migration Acide
L'influence de quelques facteurs environnementaux sur la degradation generalement consideree
comme migration acide a ete etudiee: effets de la temperature, de l'humidite et de la surface
d'exposition sur l'acidite d'echantillons de papier en contact ou a proximite de papier journal acide.
Des intercalaires "tisses" et l'encapsulation dans du mylar ont ete etudies comme possible barriere.
Les experimentations ont montre une degradation significative par migration: elle est acceleree
lorsqu'il y a augmentation de la temperature et de 1'humidite. Bien que l'encapsulation ait protege
les echantillons des substances volatiles externes, elle a accelere la vitesse de degradation lorsque
des substances volatiles internes etaient presentes. Des intercalaires alcalins ont seulement empeche
la migration a des humidiles relatives elevees alors que des intercalaires non alcalins etaient
inefficaces dans tous les cas.
Untersuckung von Einflüssen der Umwell auf den Ahbau von Papier als Folge von
Schadstoffwanderungen
Der Einllußvon Faktoren der Umgebung auf den Abhauprozess eines Objektes, gewöhnlich
bezeichnet als "Wanderung von Säure" wurde untersucht, d.h. die Auswirkungen von Hitze,
Feuchtigkeit und Säuregehali von Papier in Kontakt mit oder in Nähe von säuiehaltigem Zeitungspapier. Zwischenlagen-Papier und Hüllen aus Polyester (Mylar) wurden auf mögliche isolierende
Eigenschaften überprüft. Es zeigte sich ein beträchtlicher Abbau durch Schadstoflwanderung, der
durch steigende Temperature und Feuchtigkeit noch beschleunigt wurde. Umhüllungen schützen
zwar die Objekte vor von außen eindringenden Schadstoffen; die in der Umhüllung
eingeschlossenen beschleunigen hingegen den Abbauprozess. Gepuffertes Zwischenlagenpapier
hemmte die Schad-stoffwanderung nur bei hoher relativer Feuchte, während ungepuflfertes gar
keine Wirkung hatte.
REFERENCES
1. Barrow, W. J.: Migration of impurities in paper. Archivum 8 (1953): 105~8.
2. Kahle, T. B.: Environmental impact of the and in brittle, hooks. Capricornus, August (1978):
2—4.
3. Salmen, N. L.: Mechanical properties of wood fibers and paper. In: Nevell, T. P. & Zeronian, S.
II., ed. Cellulose chemistry and its applications: Chichester: Ellis Horwood, 1985.
4. Copeland, J. L.: Transport properties of ionic liquids. New York: Gordon & Breach, 1974.
5. Gunha, G. M.: Conservation of library materials, Vol. 1. Metuchen, NJ: Scarecrow Press, 1971.
6. Ranby, B. G.: Weak links in polysaccharide chains as related to modified groups. Journal of
Polymer Science 53 (1961): 131-40.
7. Rydholm, S. A.: Pulping processes. New York: Interscience Publishers, 1965.
8. Daniels, V: The discolouration of paper on ageing. Paper Conservator 12 (1988): 93-100.
9. Arney, J. S., Jacobs, A. J, & Newman, R.: The influence of deacidificalion on the deterioration
of paper. Journal of the American Institute for Conservation 19 (1979): 34—41.
10. Marracine, L. M. & Kleinert, T. N.: Aging and colour reversion of bleached pulps. Svensk
Papperstid-ning65 (1962): 126-31.
11. Lyail, J.: A preliminary study of chemical methods for stabilizing lignin in groundwood paper.
In: Brommelle, N. S. & Thompson, G., cd. Science and Technology in the Service of Conservation,
IIC Preprints. Washington, DC: IIC, 1982.
12. Cain, G. E.: The chemical nature of lignin. Paper session outline, AIC conference. Washington
DC: AIC, 1983.
13. Heuser, E.: The chemistry of cellulose. New York: John Wiley & Sons, 1944.
14. Desai, R. L. & Shields, J. A.: Photochemical degradation of cellulose material. Die
Makromolekuiare Chemie 22 (1969): 134-44.
15. McCrady, E.: Accelerated aging and the effects of enclosure. Abbey Newsletter April
(1984): 28-9.
16. Shahani, C. J.: Options in polyester encapsulation. A('A Bulletin 1!, I i'1986j: 20.
17. Clapp, A.: Curatorial care nj works of art on papa. Oberlin, Ohio: Intcrmuscum Conservation
Association, 1978: 69.
18. Santucci, L.: Degradation of cellulose in the presence of inorganic compounds. I. Influence of
humidity on the behavtour of cellulose containing magnesium and calcium carbonates. Bolletino
dell' Istituto Ccntrale per la Patalogia del I.ibro 32 (1973-1974): 57 72.
John Slavin, B.A.A., M.A.C.
private conservator
John Slavin Paper Conservation
204-550 Ontario Street
Toronto, Ontario M4X 1X3
Canada
Jim Hanlan, B.Sc, fvf.Sc.
Professor, Conservation Science
Art Conservation Program
Queen's University .
Kingston, Ontario K.7L 3N6
Canada