is this foxing?

[Hero Restoration]

This is real wordy but addresses the debate in great detail.

 

13.2.1 Causes

Despite investigations spanning almost sixty years there remains confusion and uncertainty as to what causes foxing, whether there is a single cause or multiple ones, and whether there is more than one type of foxing. There are currently three major explanations for foxing which have been proposed most often: a) fungal activity, b) metal-induced degradation, and c) multiple causes. Recently, a fourth explanation has been proposed which attempts to explain foxing stains within the context of general discoloration of paper caused by the interaction of moisture and cellulose.

 

Unfortunately, most of the published research on foxing neglects to provide accurate and complete information concerning size, shape, depth (within the sheet), or fluorescence pattern (or absence thereof) when describing foxing. In the future, it is hoped that investigators will use cain's proposed classification system (see 13.2.3), making it easier to integrate disparate research. Although researchers claim their stains had the “typical coloration characteristic of foxing,” this is fairly meaningless, as there is no way of judging the uniformity of this coloration. It is possible that researchers are finding different causes for foxing because the spots tested are different, even though they are all termed “foxing”. Hey has even suggested removing metal induced foxing from the foxing category altogether as this is “metal induced degradation”. Additionally, researchers proposing one cause over another often neglect to investigate both causes equally, lending an unstated bias to their findings of which the reader must be aware. Following is a summary of investigations and theories culled from conservation literature.

 

A. Fungal Activity

There are approximately 100 fungoid species designated as ‘paper-attacking’ though some specialists suggest that many more of the more than 30,000 species of fungi would attack paper [Gallo 1963, 57; RK]. Not all of these species are necessarily associated with foxing.

Some of the micro-organisms habitually associated with paper are found in the raw materials used to form the paper. These micro-organisms can remain latent for months or years awaiting the appropriate conditions for growth. Another likely means of infection of paper is through air-borne spores.

Certain fungi have been associated not just with paper generally but with foxing spots specifically. From old books and manuscripts showing the characteristic foxed discoloration, Beckwith et al. isolated fifty-five different fungi [beckwith et al. 1940, 301]. These they sampled directly from foxed areas of the paper. From foxed spots Arai found twenty-five strains located specifically within the foxed areas of paper and, in fact, could not find evidence of the fungi in any unfoxed portions of the paper [Arai 1987, 1165]. Although these strains were all found in foxed spots, only seven were found to create browning stains in Arai's experiments.

1. Explanations

The following explanations for formation mechanisms of foxing spots by fungi have been proposed.

a. Color pigments are secreted by the mycelia, the vegetative branches of mold. These pigments have various chemical compositions but are mainly composed of carotenoids and anthraquinones [Gallo 1963, 58]. Beckwith et al. state that pigments may be only a minor cause of foxing because the chromogenic tints produced by various species of mold are not characteristic of foxing [beckwith et al. 1940, 306]. Nol et al. believe fungi produce pigments and that coloration can be intensified within a foxed spot by certain combinations of fungi species which alone may not produce strong coloration [Nol et al. 1983, 22]. This explanation does not show a clear relationship between foxing and iron.

b. According to one source, micro-organisms “develop at the expense of the glue materials forming hygroscopic areas on the paper in which the water soluble degradation products of the cellulose accumulate. They assume a red-brown color in damp surroundings” [Ambler and Finney 1957, 1141 as quoted in Gallo 1963, 26]. This theory is also consistent with Meynell and Newsam who found “foxed areas invariably showed fungal hyphae weaving around but not within individual cellulose fibers. The cellulose fibers within foxed lesions appeared normal. The lesions, however, wetted more easily than the rest of the paper and stained instantaneously with Coomassie blue, indicating the sizing was participating in the fungal growth [Meynell and Newsam 1979, 567]. This explanation is inconsistent with findings by Cain and Nol et al. who found evidence of cellulolytic activity and had to assume cellulose degradation was occurring [Cain 1983; Nol et al. 1983, 23]. This explanation shows no clear relationship between foxing and iron.

c. Specific fungi tested to date have been found to produce foxing in laboratory experiments. They do this by secreting malic and other organic acids as well as amino acids. These acids are deposited on, and then attack the cellulose and/or sizing. This produces cello-oligosaccharides and glucose which in combination with amino acids produce a browning reaction known as the Maillard reaction [Arai et al. 1988, 12]. Each ingredient alone will not induce a browning reaction, but they will in combination. This explanation does not demonstrate a clear relationship between foxing and iron.

d. Foxing is the visible sign, by production of color, of deterioration within paper. Although the breakdown of paper may result from many causes, fungi constitute a most important menace to the preservation of paper. Growth of fungi in paper and development of color are furthered by iron and by certain sizings and fillers [beckwith et al. 1940, 305]. This explanation acknowledges foxing may have multiple causes requiring some iron content for fungi to create sufficiently strong coloration.

e. The fungi produces an enzyme or ferment which brings about a chemical change. This enzyme/ferment may be diffusible when moisture is present, explaining effects visible some distance from the site of the formation of the enzyme. The enzyme, in turn, may bring about its chemical change and the products of its activity may also diffuse some distance, causing local discoloration [iiams and Beckwith 1935, 415].

It is generally known that fungal growth breaks down its support by releasing enzymes. It may be that the circumstances that cause foxing also include some form of enzyme attack of cellulose. “Once growing, fungi cause damage in several ways. Actual damage to material is caused by the release of enzymes outside the organism (extracellular enzymes). These enzymes break down long-chain molecules such as cellulose or proteins into chemical units sufficiently small to be absorbed through the cell membrane into the cell. The action of extracellular enzymes is independent of the fungus; they can act even if the organism is killed or removed” [Allsop 1985, 532]. This explanation shows no relationship between foxing and iron.

2. Types

The following fungi have been cultured specifically from foxing spots and create new browning stains when reinoculated into paper under laboratory conditions.

a. Beckwith et al. [1940, 301] list genus

1. Alternaria

2. Aspergillus

3. Byssochlamys

4. Chaetomium

5. Fusarium

6. Hormodendrum

7. Monilia

8. Mucor

9. Penicillium

10. Stemphylium

b. Arai [1987, 1166] lists species

1. Aspergillus penicilloides

2. Eurotium herbariorum

c. Nol et al. [1983, 22] lists species

1. Aspergillus carneus

2. Aspergillus flavus Link (with Sclerotia)

3. Aspergillus flavus Link (lacking Sclerotia)

4. Aspergillus fumigatus Thom

5. Aspergillus niger van Tieghem

6. Aspergillus terreus var. aureus Thom & Raper

7. Aspergillus tamarii

8. Gliocladium roseum (Link) Thom

9. Penicillium funiculosum Thom

d. Cain et al. [1987, 24] found species Aspargillus repens

3. Factors favoring growth and/or color formation

a. Relative Humidity (RH)

There is no minimum degree of RH for growth of all fungi as the level varies not only with the genus but with the species as well [beckwith et al. 1940, 311–313]. The more hygroscopic the material (i.e. paper vs. leather) the lower the room RH can be in order to permit microbial growth [Gallo 1963, 59]. It is important to remember that a micro-climate, vastly different from the overall room RH, can exist within the paper's structure. Unsized tissues, for example, interleaved into books may absorb and retain water over a long period of time creating localized high humidity relative to atmosphere; this could enable fungus to develop even when surrounding RH is below 75%. Fungal hyphae may transport water from higher to lower areas of RH, perhaps centimeters away [RK].

Most research directed at microbial growth on paper shows that below 70–75% RH the chances of growth for many “paper-attacking species” of fungi is low. Arai found that below 75% RH, germination of mold spores of the type isolated from foxed spots is unlikely to occur. Interestingly Arai also found that 84% relative humidity induced growth better than 94% RH, though this is specific to the particular fungi he isolated [Arai et al. 1990, 805]. Beckwith et al. also found that below 75% they could not produce any fungal growth with the particular species they cultured [beckwith et al. 1940, 313]. In contrast to this, Nol et al. found three strains, previously isolated from foxed spots, which grew at 55% to 93.5–96% RH. Two of these strains also grew at 32.5% RH. However, foxing or coloration occurred only with one strain under RH conditions ranging from 32.5% to 96% [Nol et al. 1983, 24].

b. Temperature

Each species has its optimum temperature for growth. Generally, it has been found that growth increases with increasing temperature and decreases with decreasing temperature. Excessive heat kills most fungi and steam is a standard means of sterilizing cultures in lab procedures.

c. pH

All research has shown that foxing stains are more acidic than the surrounding paper [see, for example, Arai 1980; Hey 1983; Iiams and Beckwith 1935].

Arai's research suggests that the presence of amino acids is necessary when inducing foxing and that increasing the concentration the of amino acids results in darker brown spots [Arai et al. 1990].

d. Nutrients

Fungi may find nutrients in one or more of the following.

1. Cellulose

While some researchers insist that cellulose is not damaged in foxed areas [Meynell and Newsam 1979, 567], others have shown conclusively that fungi digest the cellulose [Cain 1983, 16 and Nol et al. 1983, 23].

2. Sizings and Adhesives

Because they saw no damage to fibers, Meynell and Newsam claim foxing feeds on gelatin size, not on the cellulose [Meynell and Newsam 1978, 467]. However, observations have also been made that fungi prefer more hygroscopic, unsized papers to those that are sized [Meynell and Newsam 1978, 468; Gallo 1963, 58].

Investigation into the influence of fillers and sizes on fungal growth and its production of acids found the following: gelatin, starch and dextrins promoted growth and color production [beckwith et al. 1940, 3307]. There was less acid production by fungi feeding on casein and rosin than with starch or cellulose alone.

3. Oils

Either from the medium of printing ink in a text or that transferred to paper by readers' or handlers' hands [Meynell and Newsam 1978, 467].

4. Micro-dust

e. Light Intensity

Generally, the growth rates for most fungi are not sensitive to light intensity. However, no study has been made of the relationship of foxing stains to light.

“Examination of a 1896 thirty-four volume set of Balzac's works on laid cotton paper found ‘snowflake’ fungal foxing in circulated volumes no different from that present in 1896 uncirculated, unopened volumes. Previously uncut pages were slit in the dark and examined in the first light exposure in nearly ninety years. Apparently dark storage produced the same pattern, color, and frequency of foxing as occasional exposure to light [Cain, Stanley and Roberts 1987, 24].

B. Metal-Induced Degradation

“Cellulose is directly oxidized catalytically in the presence of iron, copper, and cobalt compounds, and the reaction is most rapid at high humidities” [Tang 1978, 19]. Metal impurities in paper, specifically iron and copper, are believed to result from particles abraded from the metal equipment and/or from contaminated water used in the papermaking process. Additionally, all wood-pulp paper may be expected to contain iron, as it is naturally present in wood [beckwith et al. 1940, 302].

“In ‘bullseye’ copper-or iron-induced foxing the role of these two metals is probably that of oxidative catalyst. Both metals can undergo reversible oxidation-reduction. For example, they are both found playing such a role in metabolic biochemical reactions. Iron can alternately be oxidized from the +2 (ferrous) state to the +3 (ferric) state and then be reduced back to the +2 state as it plays the role of oxidizer. Copper can do the same between the +1 and +2 states. Thin-layer chromatographic studies show the extracts of ‘bullseye’ foxed and unfoxed paper to have all or most of the same bands. This further suggests iron and copper act to catalyze (accelerate) the oxidative degradation of paper” [Cain 1983, 15; Cain and Kalasinski 1987, 57]. In a tally of metal-induced foxing, analysis showed that twenty-seven were induced by copper and copper alloys to over 200 induced by iron [Cain and Miller 1982, 7].

1. Iron

a. Coloration

“The very color of foxing connotes the presence of iron” [iiams and Beckwith 1935, 412]. Iron ions create yellow-brown spots and Tang found that “there is a trend for darkness of the foxing spot to increase with increasing iron content; the highest concentration of iron was noted in the center of the spots, with the metal concentration decreasing... as the distance increased from the center” [Tang 1978, 24, 26].

b. Occurrence

It would be very difficult to find any paper without some degree of iron [MH]. Numerous researchers have identified iron ions within foxing stains and found a significantly greater concentration of iron in the foxed areas compared to surrounding paper [Cain 1983, Cain 1988, Cain and Miller 1982, Cain and Miller 1984, Daniels 1988, Gallo and Hey 1988, Tang 1978, Tang and Troyer 1981]. One study, however, found no difference between foxed and unfoxed areas [Press 1976, 29]. This was corroborated by Tang, who found that in some foxed papers there was no difference in iron (or other metal ion) concentration [Tang 1978, 28]. While concentrations greater than 500 ppm have been identified with undesirable spots, Hey suggests that “if iron is involved it is not its total concentration that is important but rather its availability to participate in reactions or its effective solubility” [Tang 1978, 28; Hey 1983, 341].

c. Form

Research indicates that iron in paper is found entirely in the ferric, rather than ferrous, form [beckwith et al. 1940, 303].

d. Activation

Iron will not corrode below 70% RH, but in the presence of ions such as chloride, storage needs to be at 40% RH or lower to avoid corrosion. Hey suggests that “there is a strong chemical possibility that heavy metals present in the paper in a quiescent state will be activated by washing with an acid water, when this is not followed by deacidification” [Hey 1979, 68].

2. Copper

Daniels and Meeks describe copper-related foxing as varying in size “from small spots with no apparent nucleus and only a brown diffuse discolouration, to large spots of about 5 mm diameter with black dendritic patterns or green corrosion products; these spots include an outer ring of brown discoloured paper” [Daniels and Meeks nd., 2]. Analysis by EDX revealed that the foxed areas contained copper, zinc, sulfur, and chlorine, while the unfoxed areas “did not have detectable amounts of these elements” [Daniels and Meeks nd., 5; see 13.2.4.E.2]. It was concluded that chloride ions, from original or subsequent bleaching residues, accelerated the corrosion of brass (a copper/zinc alloy) inclusions in the paper. The soluble copper compound was then able to react with hydrogen sulfide generated in the paper or absorbed from the atmosphere. The stain was due to a combination of black copper sulfide and brown copper catalyzed degraded cellulose [Daniels and Meeks nd., 8]. Tang linked copper concentrations greater than 50 ppm with formation of undesirable spots [Tang 1978, 28].

C. Condensation

A modification of the cellulose, often visually evident by browning, which takes place at the interface between wet and dry parts of fibrous materials and which is not the result of degradation products being carried and deposited by a spreading liquid. “Experiments suggest that the interaction of air, water and cellulose is responsible for the formation of browning” [Hutchins 1983, 58]. This interaction could occur at sites of temporary moisture accumulation in the paper. “Depending on the moisture content of a book, [for example,] it would be possible for uniform discolouration of zones, as well as smaller or larger stains, to develop. All the possible factors that influence condensation and evaporation would play a role in this: humidity, temperature, air pressure, paper porosity, and any irregularities in the paper which could include folds, tears, and dirt particles; even the presence of concentrations of iron or fungus could likewise induce condensation” [Ligterink et al. 1991, 51].

The above authors speculate on the relationship between foxing and other forms of discoloration (text block areas, leaf margins). The link is based on observations of both types of staining (foxing and zonal) appearing together on the same page in many books.

The condensation explanation for browning is a broad view ascribing moisture and cellulose and possibly oxygen as the only necessary ingredients to achieve staining. The presence of fungi and/or metals would act only as attractive sites for moisture and consequent browning.

D. Multiple Causes

Given the ubiquitous nature of both iron and fungi in paper it is quite possible they often act in tandem. Research appears divided (fungal infection vs. metal-induced degradation), and one must keep in mind, when reviewing each study, whether the presence of a dual cause was fully investigated. Often researchers did not adequately test for iron when they found fungi and vice versa.

A good example of this is the use of the SEM. Where Cain and Miller did not, in one study, find an iron core using SEM and EDX, they successfully located it using narrow beam x-ray fluorescence [see 13.2.4.F.1–3]. Other research, however, has relied on SEM alone to determine that there was no iron (or other metals) present without using other methods to check their results.

As early as 1935, Iiams and Beckwith proposed a dual cause of spot formation: organic acids secreted by the metabolizing fungi react with iron present (even in trace amounts) in the paper to form unstable organic iron salts (organo-ferro compounds) which decompose to form iron oxides and hydroxides i.e. brown/rust coloration [iiams and Beckwith 1935, 414].

Iiams and Beckwith also found that adding a 1:1,000 solution of iron caused fungal growth which “greatly exceeded any that had been produced in the laboratory without the presence of iron in the culture papers” [iiams and Beckwith 1935, 414]. Their later research confirmed this as well as showing that iron increases the degree and intensity of the discoloration which accompanies fungal proliferation [beckwith et al. 1940, 303–306]. The resulting brown tint had the color of ferric oxide. The presence of casein, gelatin, and starch add to the discoloring effects of iron.

Hey concurred with Iiams and Beckwith and proposed these dual mechanisms:

1. damp -> mold acid -> activation of iron -> increased acid -> mold death

2. damp -> activation of iron -> increased acidity -> local encouragement of mold -> increased acidity -> death of mold [Hey 1983, 341]

These models suggest that one reason why foxing stains do not cover an entire page might be that the acids secreted by the fungi collect, eventually reducing the pH enough to curtail further fungal growth.

Cain and Miller found that “snowflake” foxing contained a higher iron concentration than the surrounding paper [Cain and Miller 1982, 61]. A later study found hyphae and occasional fruiting bodies in all snowflake fungal foxed areas examined [Cain, Stanley and Roberts 1987, 24]. This suggests a dual cause.

Fungi use iron and copper as co-enzymes. This means that they are essential elements. After use, the excess may be secreted (perhaps as an altered or activated ion) [RK].

[Bill Robinson]

 

This is hilariously incorrect. I won't even bother.

 

Awesome.

[divad]

This is real wordy but addresses the debate in great detail.

 

13.2.1 Causes

Despite investigations spanning almost sixty years there remains confusion and uncertainty as to what causes foxing, whether there is a single cause or multiple ones, and whether there is more than one type of foxing. There are currently three major explanations for foxing which have been proposed most often: a) fungal activity, b) metal-induced degradation, and c) multiple causes. Recently, a fourth explanation has been proposed which attempts to explain foxing stains within the context of general discoloration of paper caused by the interaction of moisture and cellulose.

 

Unfortunately, most of the published research on foxing neglects to provide accurate and complete information concerning size, shape, depth (within the sheet), or fluorescence pattern (or absence thereof) when describing foxing. In the future, it is hoped that investigators will use cain's proposed classification system (see 13.2.3), making it easier to integrate disparate research. Although researchers claim their stains had the “typical coloration characteristic of foxing,” this is fairly meaningless, as there is no way of judging the uniformity of this coloration. It is possible that researchers are finding different causes for foxing because the spots tested are different, even though they are all termed “foxing”. Hey has even suggested removing metal induced foxing from the foxing category altogether as this is “metal induced degradation”. Additionally, researchers proposing one cause over another often neglect to investigate both causes equally, lending an unstated bias to their findings of which the reader must be aware. Following is a summary of investigations and theories culled from conservation literature.

 

A. Fungal Activity

There are approximately 100 fungoid species designated as ‘paper-attacking’ though some specialists suggest that many more of the more than 30,000 species of fungi would attack paper [Gallo 1963, 57; RK]. Not all of these species are necessarily associated with foxing.

Some of the micro-organisms habitually associated with paper are found in the raw materials used to form the paper. These micro-organisms can remain latent for months or years awaiting the appropriate conditions for growth. Another likely means of infection of paper is through air-borne spores.

Certain fungi have been associated not just with paper generally but with foxing spots specifically. From old books and manuscripts showing the characteristic foxed discoloration, Beckwith et al. isolated fifty-five different fungi [beckwith et al. 1940, 301]. These they sampled directly from foxed areas of the paper. From foxed spots Arai found twenty-five strains located specifically within the foxed areas of paper and, in fact, could not find evidence of the fungi in any unfoxed portions of the paper [Arai 1987, 1165]. Although these strains were all found in foxed spots, only seven were found to create browning stains in Arai's experiments.

1. Explanations

The following explanations for formation mechanisms of foxing spots by fungi have been proposed.

a. Color pigments are secreted by the mycelia, the vegetative branches of mold. These pigments have various chemical compositions but are mainly composed of carotenoids and anthraquinones [Gallo 1963, 58]. Beckwith et al. state that pigments may be only a minor cause of foxing because the chromogenic tints produced by various species of mold are not characteristic of foxing [beckwith et al. 1940, 306]. Nol et al. believe fungi produce pigments and that coloration can be intensified within a foxed spot by certain combinations of fungi species which alone may not produce strong coloration [Nol et al. 1983, 22]. This explanation does not show a clear relationship between foxing and iron.

b. According to one source, micro-organisms “develop at the expense of the glue materials forming hygroscopic areas on the paper in which the water soluble degradation products of the cellulose accumulate. They assume a red-brown color in damp surroundings” [Ambler and Finney 1957, 1141 as quoted in Gallo 1963, 26]. This theory is also consistent with Meynell and Newsam who found “foxed areas invariably showed fungal hyphae weaving around but not within individual cellulose fibers. The cellulose fibers within foxed lesions appeared normal. The lesions, however, wetted more easily than the rest of the paper and stained instantaneously with Coomassie blue, indicating the sizing was participating in the fungal growth [Meynell and Newsam 1979, 567]. This explanation is inconsistent with findings by Cain and Nol et al. who found evidence of cellulolytic activity and had to assume cellulose degradation was occurring [Cain 1983; Nol et al. 1983, 23]. This explanation shows no clear relationship between foxing and iron.

c. Specific fungi tested to date have been found to produce foxing in laboratory experiments. They do this by secreting malic and other organic acids as well as amino acids. These acids are deposited on, and then attack the cellulose and/or sizing. This produces cello-oligosaccharides and glucose which in combination with amino acids produce a browning reaction known as the Maillard reaction [Arai et al. 1988, 12]. Each ingredient alone will not induce a browning reaction, but they will in combination. This explanation does not demonstrate a clear relationship between foxing and iron.

d. Foxing is the visible sign, by production of color, of deterioration within paper. Although the breakdown of paper may result from many causes, fungi constitute a most important menace to the preservation of paper. Growth of fungi in paper and development of color are furthered by iron and by certain sizings and fillers [beckwith et al. 1940, 305]. This explanation acknowledges foxing may have multiple causes requiring some iron content for fungi to create sufficiently strong coloration.

e. The fungi produces an enzyme or ferment which brings about a chemical change. This enzyme/ferment may be diffusible when moisture is present, explaining effects visible some distance from the site of the formation of the enzyme. The enzyme, in turn, may bring about its chemical change and the products of its activity may also diffuse some distance, causing local discoloration [iiams and Beckwith 1935, 415].

It is generally known that fungal growth breaks down its support by releasing enzymes. It may be that the circumstances that cause foxing also include some form of enzyme attack of cellulose. “Once growing, fungi cause damage in several ways. Actual damage to material is caused by the release of enzymes outside the organism (extracellular enzymes). These enzymes break down long-chain molecules such as cellulose or proteins into chemical units sufficiently small to be absorbed through the cell membrane into the cell. The action of extracellular enzymes is independent of the fungus; they can act even if the organism is killed or removed” [Allsop 1985, 532]. This explanation shows no relationship between foxing and iron.

2. Types

The following fungi have been cultured specifically from foxing spots and create new browning stains when reinoculated into paper under laboratory conditions.

a. Beckwith et al. [1940, 301] list genus

1. Alternaria

2. Aspergillus

3. Byssochlamys

4. Chaetomium

5. Fusarium

6. Hormodendrum

7. Monilia

8. Mucor

9. Penicillium

10. Stemphylium

b. Arai [1987, 1166] lists species

1. Aspergillus penicilloides

2. Eurotium herbariorum

c. Nol et al. [1983, 22] lists species

1. Aspergillus carneus

2. Aspergillus flavus Link (with Sclerotia)

3. Aspergillus flavus Link (lacking Sclerotia)

4. Aspergillus fumigatus Thom

5. Aspergillus niger van Tieghem

6. Aspergillus terreus var. aureus Thom & Raper

7. Aspergillus tamarii

8. Gliocladium roseum (Link) Thom

9. Penicillium funiculosum Thom

d. Cain et al. [1987, 24] found species Aspargillus repens

3. Factors favoring growth and/or color formation

a. Relative Humidity (RH)

There is no minimum degree of RH for growth of all fungi as the level varies not only with the genus but with the species as well [beckwith et al. 1940, 311–313]. The more hygroscopic the material (i.e. paper vs. leather) the lower the room RH can be in order to permit microbial growth [Gallo 1963, 59]. It is important to remember that a micro-climate, vastly different from the overall room RH, can exist within the paper's structure. Unsized tissues, for example, interleaved into books may absorb and retain water over a long period of time creating localized high humidity relative to atmosphere; this could enable fungus to develop even when surrounding RH is below 75%. Fungal hyphae may transport water from higher to lower areas of RH, perhaps centimeters away [RK].

Most research directed at microbial growth on paper shows that below 70–75% RH the chances of growth for many “paper-attacking species” of fungi is low. Arai found that below 75% RH, germination of mold spores of the type isolated from foxed spots is unlikely to occur. Interestingly Arai also found that 84% relative humidity induced growth better than 94% RH, though this is specific to the particular fungi he isolated [Arai et al. 1990, 805]. Beckwith et al. also found that below 75% they could not produce any fungal growth with the particular species they cultured [beckwith et al. 1940, 313]. In contrast to this, Nol et al. found three strains, previously isolated from foxed spots, which grew at 55% to 93.5–96% RH. Two of these strains also grew at 32.5% RH. However, foxing or coloration occurred only with one strain under RH conditions ranging from 32.5% to 96% [Nol et al. 1983, 24].

b. Temperature

Each species has its optimum temperature for growth. Generally, it has been found that growth increases with increasing temperature and decreases with decreasing temperature. Excessive heat kills most fungi and steam is a standard means of sterilizing cultures in lab procedures.

c. pH

All research has shown that foxing stains are more acidic than the surrounding paper [see, for example, Arai 1980; Hey 1983; Iiams and Beckwith 1935].

Arai's research suggests that the presence of amino acids is necessary when inducing foxing and that increasing the concentration the of amino acids results in darker brown spots [Arai et al. 1990].

d. Nutrients

Fungi may find nutrients in one or more of the following.

1. Cellulose

While some researchers insist that cellulose is not damaged in foxed areas [Meynell and Newsam 1979, 567], others have shown conclusively that fungi digest the cellulose [Cain 1983, 16 and Nol et al. 1983, 23].

2. Sizings and Adhesives

Because they saw no damage to fibers, Meynell and Newsam claim foxing feeds on gelatin size, not on the cellulose [Meynell and Newsam 1978, 467]. However, observations have also been made that fungi prefer more hygroscopic, unsized papers to those that are sized [Meynell and Newsam 1978, 468; Gallo 1963, 58].

Investigation into the influence of fillers and sizes on fungal growth and its production of acids found the following: gelatin, starch and dextrins promoted growth and color production [beckwith et al. 1940, 3307]. There was less acid production by fungi feeding on casein and rosin than with starch or cellulose alone.

3. Oils

Either from the medium of printing ink in a text or that transferred to paper by readers' or handlers' hands [Meynell and Newsam 1978, 467].

4. Micro-dust

e. Light Intensity

Generally, the growth rates for most fungi are not sensitive to light intensity. However, no study has been made of the relationship of foxing stains to light.

“Examination of a 1896 thirty-four volume set of Balzac's works on laid cotton paper found ‘snowflake’ fungal foxing in circulated volumes no different from that present in 1896 uncirculated, unopened volumes. Previously uncut pages were slit in the dark and examined in the first light exposure in nearly ninety years. Apparently dark storage produced the same pattern, color, and frequency of foxing as occasional exposure to light [Cain, Stanley and Roberts 1987, 24].

B. Metal-Induced Degradation

“Cellulose is directly oxidized catalytically in the presence of iron, copper, and cobalt compounds, and the reaction is most rapid at high humidities” [Tang 1978, 19]. Metal impurities in paper, specifically iron and copper, are believed to result from particles abraded from the metal equipment and/or from contaminated water used in the papermaking process. Additionally, all wood-pulp paper may be expected to contain iron, as it is naturally present in wood [beckwith et al. 1940, 302].

“In ‘bullseye’ copper-or iron-induced foxing the role of these two metals is probably that of oxidative catalyst. Both metals can undergo reversible oxidation-reduction. For example, they are both found playing such a role in metabolic biochemical reactions. Iron can alternately be oxidized from the +2 (ferrous) state to the +3 (ferric) state and then be reduced back to the +2 state as it plays the role of oxidizer. Copper can do the same between the +1 and +2 states. Thin-layer chromatographic studies show the extracts of ‘bullseye’ foxed and unfoxed paper to have all or most of the same bands. This further suggests iron and copper act to catalyze (accelerate) the oxidative degradation of paper” [Cain 1983, 15; Cain and Kalasinski 1987, 57]. In a tally of metal-induced foxing, analysis showed that twenty-seven were induced by copper and copper alloys to over 200 induced by iron [Cain and Miller 1982, 7].

1. Iron

a. Coloration

“The very color of foxing connotes the presence of iron” [iiams and Beckwith 1935, 412]. Iron ions create yellow-brown spots and Tang found that “there is a trend for darkness of the foxing spot to increase with increasing iron content; the highest concentration of iron was noted in the center of the spots, with the metal concentration decreasing... as the distance increased from the center” [Tang 1978, 24, 26].

b. Occurrence

It would be very difficult to find any paper without some degree of iron [MH]. Numerous researchers have identified iron ions within foxing stains and found a significantly greater concentration of iron in the foxed areas compared to surrounding paper [Cain 1983, Cain 1988, Cain and Miller 1982, Cain and Miller 1984, Daniels 1988, Gallo and Hey 1988, Tang 1978, Tang and Troyer 1981]. One study, however, found no difference between foxed and unfoxed areas [Press 1976, 29]. This was corroborated by Tang, who found that in some foxed papers there was no difference in iron (or other metal ion) concentration [Tang 1978, 28]. While concentrations greater than 500 ppm have been identified with undesirable spots, Hey suggests that “if iron is involved it is not its total concentration that is important but rather its availability to participate in reactions or its effective solubility” [Tang 1978, 28; Hey 1983, 341].

c. Form

Research indicates that iron in paper is found entirely in the ferric, rather than ferrous, form [beckwith et al. 1940, 303].

d. Activation

Iron will not corrode below 70% RH, but in the presence of ions such as chloride, storage needs to be at 40% RH or lower to avoid corrosion. Hey suggests that “there is a strong chemical possibility that heavy metals present in the paper in a quiescent state will be activated by washing with an acid water, when this is not followed by deacidification” [Hey 1979, 68].

2. Copper

Daniels and Meeks describe copper-related foxing as varying in size “from small spots with no apparent nucleus and only a brown diffuse discolouration, to large spots of about 5 mm diameter with black dendritic patterns or green corrosion products; these spots include an outer ring of brown discoloured paper” [Daniels and Meeks nd., 2]. Analysis by EDX revealed that the foxed areas contained copper, zinc, sulfur, and chlorine, while the unfoxed areas “did not have detectable amounts of these elements” [Daniels and Meeks nd., 5; see 13.2.4.E.2]. It was concluded that chloride ions, from original or subsequent bleaching residues, accelerated the corrosion of brass (a copper/zinc alloy) inclusions in the paper. The soluble copper compound was then able to react with hydrogen sulfide generated in the paper or absorbed from the atmosphere. The stain was due to a combination of black copper sulfide and brown copper catalyzed degraded cellulose [Daniels and Meeks nd., 8]. Tang linked copper concentrations greater than 50 ppm with formation of undesirable spots [Tang 1978, 28].

C. Condensation

A modification of the cellulose, often visually evident by browning, which takes place at the interface between wet and dry parts of fibrous materials and which is not the result of degradation products being carried and deposited by a spreading liquid. “Experiments suggest that the interaction of air, water and cellulose is responsible for the formation of browning” [Hutchins 1983, 58]. This interaction could occur at sites of temporary moisture accumulation in the paper. “Depending on the moisture content of a book, [for example,] it would be possible for uniform discolouration of zones, as well as smaller or larger stains, to develop. All the possible factors that influence condensation and evaporation would play a role in this: humidity, temperature, air pressure, paper porosity, and any irregularities in the paper which could include folds, tears, and dirt particles; even the presence of concentrations of iron or fungus could likewise induce condensation” [Ligterink et al. 1991, 51].

The above authors speculate on the relationship between foxing and other forms of discoloration (text block areas, leaf margins). The link is based on observations of both types of staining (foxing and zonal) appearing together on the same page in many books.

The condensation explanation for browning is a broad view ascribing moisture and cellulose and possibly oxygen as the only necessary ingredients to achieve staining. The presence of fungi and/or metals would act only as attractive sites for moisture and consequent browning.

D. Multiple Causes

Given the ubiquitous nature of both iron and fungi in paper it is quite possible they often act in tandem. Research appears divided (fungal infection vs. metal-induced degradation), and one must keep in mind, when reviewing each study, whether the presence of a dual cause was fully investigated. Often researchers did not adequately test for iron when they found fungi and vice versa.

A good example of this is the use of the SEM. Where Cain and Miller did not, in one study, find an iron core using SEM and EDX, they successfully located it using narrow beam x-ray fluorescence [see 13.2.4.F.1–3]. Other research, however, has relied on SEM alone to determine that there was no iron (or other metals) present without using other methods to check their results.

As early as 1935, Iiams and Beckwith proposed a dual cause of spot formation: organic acids secreted by the metabolizing fungi react with iron present (even in trace amounts) in the paper to form unstable organic iron salts (organo-ferro compounds) which decompose to form iron oxides and hydroxides i.e. brown/rust coloration [iiams and Beckwith 1935, 414].

Iiams and Beckwith also found that adding a 1:1,000 solution of iron caused fungal growth which “greatly exceeded any that had been produced in the laboratory without the presence of iron in the culture papers” [iiams and Beckwith 1935, 414]. Their later research confirmed this as well as showing that iron increases the degree and intensity of the discoloration which accompanies fungal proliferation [beckwith et al. 1940, 303–306]. The resulting brown tint had the color of ferric oxide. The presence of casein, gelatin, and starch add to the discoloring effects of iron.

Hey concurred with Iiams and Beckwith and proposed these dual mechanisms:

1. damp -> mold acid -> activation of iron -> increased acid -> mold death

2. damp -> activation of iron -> increased acidity -> local encouragement of mold -> increased acidity -> death of mold [Hey 1983, 341]

These models suggest that one reason why foxing stains do not cover an entire page might be that the acids secreted by the fungi collect, eventually reducing the pH enough to curtail further fungal growth.

Cain and Miller found that “snowflake” foxing contained a higher iron concentration than the surrounding paper [Cain and Miller 1982, 61]. A later study found hyphae and occasional fruiting bodies in all snowflake fungal foxed areas examined [Cain, Stanley and Roberts 1987, 24]. This suggests a dual cause.

Fungi use iron and copper as co-enzymes. This means that they are essential elements. After use, the excess may be secreted (perhaps as an altered or activated ion) [RK].

 

This is a great summary (thumbs u What's the citation?

[divad]

 

This is hilariously incorrect. I won't even bother.

 

Awesome.

 

This is not. Bill, why don't you try contributing something?

[Hero Restoration]

 

This is a great summary (thumbs u What's the citation?

 

 

 

 

 

Book & Paper Conservation Catalog

13. Foxing

 

 

 

Date: 2/13/92

 

Compilers: Antoinette Owen and Jonathan Derow

Contributors: Anne Driesse, Antoinette King, Betty Fiske, C. Eugene Cain, Deborah D. Mayer, Elizabeth Morse, John Krill, Judy Walsh, Katherine Eirk, Kendra D. Lovette, Kitty Nicholson, Margaret Hey, Margaret Holben Ellis, Nancy Heugh, Patricia Dacus Hamm, Paula Volent, Rachel Danzing, Reba Fishman, Robert J. Koestler, Sarah Bertalan, Sarah C. Riley

Questionnaire Respondents: Betty Fiske, Elizabeth Morse, Helen Otis, Katherine Eirk, Margaret Holben Ellis, Margaret Lawson, Marjorie Shelley, Nancy Heugh, Paula Volent.

Editorial Board Liaison: Sarah Bertalan

Editorial Board: Antoinette Dwan, Ann Seibert, Catherine I. Maynor, Catherine Nicholson, Dianne van der Reyden, Kimberly Schenck, Sarah Bertalan, Sylvia Rodgers Albro, Terry Boone Wallis

 

[divad]

(thumbs u

[Bill Robinson]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

 

[asteroid-comix]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

Then tell us what you've learned Bill

 

Perhaps some reading David's comment thought it was spot on. I'm not sure you could mearly wash away foxing by creating an "alkaline reserve followed by a Hypochlorite solution". Good theory on the part of MPC, but it falls apart when you consider that foxing is a fungi and it does not reside mearly on the top of the paper, but actually penetrates the paper. Any type of chemical wash is going to leave those sections of the paper stained, weak, and damaged.

[Hero Restoration]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

Then tell us what you've learned Bill

 

Perhaps some reading David's comment thought it was spot on. I'm not sure you could mearly wash away foxing by creating an "alkaline reserve followed by a Hypochlorite solution". Good theory on the part of MPC, but it falls apart when you consider that foxing is a fungi and it does not reside mearly on the top of the paper, but actually penetrates the paper. Any type of chemical wash is going to leave those sections of the paper stained, weak, and damaged.

 

I realize my statement was inacurate but it did come from information somewhat along the lines of what I was saying. I was really trying to give the short answer but here is more wordy explainations of how to treat foxing.

 

 

13.4.1 Environment

A. Housing

There is some experimental evidence that foxing will worsen over time if kept in a poor environment. As for any other damaged, brittle or inherently fragile materials, proper housing with non-acidic or buffered materials, non-damaging RH and temperatures and limited handling and exposure must be considered the first treatment step, which may mitigate further damage [beckwith and Iiams 1935, 415–16].

B. Relative Humidity (RH)

Storing paper at a low RH is recommended as “the best precaution against foxing” [Daniels 1988, 93]. See 13.2.1.A.3.a and 13.2.1.B.1.d.

C. Temperature

Fungi generally prefer temperatures of 25°C to 35°C, dependent on species. There is no indication that iron corrosion is temperature dependent. Often temperature in storage or exhibition spaces is determined by comfort zones for people, and it is therefore easier to regulate RH to avoid conditions which may further damage paper.

D. Ventilation

Good circulation is often mentioned as a deterrent to mold and air borne fungi especially in articles relating to libraries [Allsop 1985, 533].

13.4.2 No Intervention

Walsh rightly notes that “foxing patterns do not always constitute a disfigurement to a work of art.” She indicates a charcoal-and-ink wash drawing by Daumier in which the artist executed the work on a sheet of foxed paper and incorporated the snowflake pattern into his design [Walsh 1985, 8]. Some papermaking historians feel that metallic inclusions are part of the paper's history and should not be removed [RF].

 

Harding found that works of art on prepared paper (e.g. Silverpoint) were “in general not susceptible to foxing, although one or two fox marks may occasionally be evident. It would be very unwise to attempt removal of the spots, as this would normally involve the localised application of aqueous solutions... inevitably result[ing] in an unsightly spot with a surrounding halo, and disruption of the reflective properties of the surface of the drawing” [Harding 1986, 26].

 

13.4.3 Fungicides

Most conservators do not use fungicides. Though a variety of substances have been used as fungicidal fumigants (thymol, ortho-phenylphenol, etc.), none are actually fungicides as such (though one specialist maintains that ortho-phenylphenol is fungicidal [RK]). Rather, they are fungistatic, inhibiting fungal growth only while the toxin is present. Dissipation or evaporation of the substance will allow fungal growth to continue. A true fungicide would kill all fungi and spores on contact [Haines and Kohler 1986, 50].

 

13.4.4 Alkaline Washes

A. Neutralisation of Acidity

As mentioned above, both fungal action and metal ion catalysis will result in acidic degradation products. To prevent further acid-catalyzed hydrolysis of paper these should be neutralized.

Beckwith et al. state that the intensity of color is greater in an acidic environment than when a sheet is alkaline. This indicates that imparting an alkaline reserve during sheet formation might reduce the severity of future discoloration [beckwith et al. 1940, 311].

B. Reduction of Staining

Beckwith et al. determined that the content of material soluble in a weak base (4% aqueous solution of ammonium hydroxide) increased markedly in foxed areas as compared to unfoxed, and that this material is hygroscopic [beckwith et al. 1940, 322]. This may in part explain why foxed areas in paper absorb moisture first and most completely when a sheet is moistened. Gallo and Hey found that washing with alkaline water can attenuate, if not completely remove, many foxing marks. Deacidification, with half-saturated calcium hydroxide solution, was even more satisfactory [Gallo and Hey 1988, 102]. However, many conservators would consider the pH of this solution too high [AK]. Percentages as high as the four percent used by Beckwith et al. are not recommended for treating works of art on paper, though less concentrated alkaline solutions have been found useful for reducing foxing.

C. Treatment of Metal Ions

It is believed that both calcium and magnesium compounds form stable complexes with the transition metals (eg. iron and copper) and by so doing “person_having_a_hard_time_understanding_my_point cellulose depolymerization by deactivating the transition metal catalysis”, it should be noted that “magnesium [carbonate] is a more effective stabilizer than calcium carbonate” [Williams et al. 1977, 49; 57–58]. Hey believes this statement to be somewhat misleading and discusses reasons why calcium carbonate is the better choice for depositing and alkaline reserve [Hey 1979, 78–9]. It is believed that imparting an alkaline reserve in the paper will prevent metallic ions from catalyzing cellulose degradation, though this may not prevent degradation and discoloration of the metal itself [Tang and Troyer 1981, 44]. When the reserve has been used up by the paper, metallic catalyzed deterioration of cellulose may resume [JK]. Tang and Troyer found both calcium hydroxide and magnesium bicarbonate ineffective in removing copper from handmade papers. Only ammonium carbonate significantly reduced the copper content.

D. Pre-Treatment for Bleaching

Conservators often find alkaline washing of foxing (either localized on the suction table or by immersion) a good pre-treatment for bleaching. Not only does this sufficiently diminish foxing stains in many cases, it may help to inactivate metal ions if present. Alkaline washes are also used to raise paper pH so that the bleach can be used in the least damaging pH range. If iron is present and hydrogen peroxide is the bleach of choice, this would be a prerequisite. Conservators have employed the following solutions for alkaline washing or deacidification: calcium or magnesium carbonate and bicarbonate, calcium or magnesium hydroxide, and ammonium hydroxide.

13.4.5 Metal Removal or Inactivation

Metal related foxing, particularly that with a visible metal core, cannot be successfully inactivated by bleaching alone, though the staining may be reduced or eliminated. Conservation literature indicates that in order to prevent future metal-catalyzed oxidation of the cellulose, the metal should be mechanically and/or chemically removed, or rendered inactive. In practise, few conservators are currently using chelating agents to do this. Another suggested measure to render metals inactive is controlled environment (especially humidity) and proper housing.

 

A. Mechanical

Iron particles in the paper can be physically removed with a scalpel under a microscope. It has been recommended that such treatment should be followed by chemical treatment to remove any residual iron particles lodged in the fibers and to remove any staining that might have surrounded the particle. If any iron/metal is left in the fibers, it will eventually re-oxidize and the stain will reappear [burgess 1988, 24].

B. Chemical

There have been several suggestions for decolorizing, complexing, or chelating metal impurities in paper.

1. Sodium Dithionite (Hydrosulfite)

A 2–10% aqueous solution will convert the insoluble colored ferric ion (Fe+++) to the more soluble colorless ferrous ion (Fe++). Subsequent washing with a Fe++ specific chelating agent will remove the ferrous ions from the paper and should prevent color reversion [burgess 1988, 24, See PCC 19.3.3.B.] Burgess also notes that the colorless ferrous iron can be removed by simple water washing, a chelating agent, however, would speed the process. If colorless ferrous salts are allowed to remain in the paper, they will “in time be oxidized by atmospheric oxygen back to the colored ferric compounds” [burgess 1991, 33]. “Sodium hydrosulphite appears to be a relatively safe agent in that it does not substantially yellow paper, weaken it, or alter it's pH” [Hawlye, Kawai and Sergeant 1981, 21].

See also PCC 19.3.3.B.

2. Chelating Agents: These have been used extensively in the paper industry and only recently has some research been directed towards their use in paper conservation [burgess 1991].

a. EDTA and Related Compounds

Ferric or ferrous ion specific chelating agents have been successfully used to sequester and remove iron from paper, though generally in conjunction with a reducing agent. “Chelating reactions work fastest when both the chelating agent and the metal to be chelated are present in solution...An extremely good way to use chelating agents to remove iron is to couple them with another process which involves the reduction of the insoluble ferric ion to the more water soluble ferrous form. The conclusion is that chelation as a single process will not always be an ideal way to approach removal of iron stains. Even in relatively concentrated solution, [chelating agents] do not seem to work very well...[due to] the low solubility of iron oxides and hydroxides” [burgess 1991, 39]. Further research in the efficacy of ferric reagents such as Fe3 Specific (Dow Chemical Corp) would be beneficial.

b. Oxalic Acid

This was often recommended in the literature for removing iron stains, but it is highly acidic and its use is not advised. See Hawley, Kawai and Sergeant 1981.

3. Alkaline treatment of metal ions (See 13.4.3.C).

4. Acid Solubilization

“Examples of acids which can solubilize iron are oxalic [see 13.4.4.B.2.b] or acetic acid. Home remedies such as vinegar or lemon juice have also been used in the past. Providing the acid is strong enough, iron removal will be relatively quick and complete. However, subjecting paper artefacts to pH between 0 and 4 can, and usually will, do considerable damage...Therefore, the use of acids to remove iron stains is now discouraged” [burgess 1991, 39].

13.4.5 Bleaching

Bleaching would not remove metal impurities and may result in local metal-catalyzed degradation. This may explain the reappearance of metal-related foxing after bleaching treatment. The recurrence of stains after bleaching treatment may also be due to improper use of bleaching solutions, inadequate pre-treatment, or inadequate rinsing. While visible discoloration may disappear as a result of bleaching, florescence under UV will continue [Meynell and Newsam 1978, 467].

 

Special attention should be taken when bleaching foxed areas, as the cellulose in these areas is generally more degraded than in surrounding areas and will be further weakened by oxidative bleaches.

 

A. Chlorine Dioxide

Treatment can be either gaseous or aqueous. It has been found that this bleach will “often decolorize severe foxing without as much degradation or color reversion as the hypochlorites” [PCC 19.3.1.D]. Burgess emphasizes the importance of washing after treatment, whether gas phase or immersion bleaching has been employed, to remove bleaching residues and solubilized discoloration products [burgess 1988, 22]. This bleach is the least affected by trace metal elements in the paper.

Meynell found that ClO2 was successful in reducing foxing, though he was often left with a “light biscuit-coloured patch” rather than a total disappearance of the stain [Meynell 1979, 31].

See also PCC 19.3.1.D.

B. Hydrogen Peroxide

The degradation of paper can be excessive if unstabilized hydrogen peroxide is used, particularly when metal-induced foxing is the cause of the staining being bleached. Stabilizers in the hydrogen peroxide will help prevent metal catalyzed breakdown of the bleach solution and therefore lessen cellulose degradation during the procedure. Stabilizers such as magnesium silicates and hydroxides used in hydrogen peroxide function similar to chelating agents in that they act to complex metals and prevent them from participating in chemical reactions [burgess 1991, 42]. Probably even stabilized hydrogen peroxide should not be used on paper with conspicuous stains of heavy metals (e.g. iron, copper) or their salts or oxides unless complexing of these metals within the paper has also been undertaken.

This bleach is commonly used by conservators for foxing stains, though most do warn against it if they believe iron is present. Presumably, this assessment would be based solely on examination by visible or transmitted light, as most conservators reported that they rarely, if ever, used UV when examining foxing. The research has shown that all bullseye foxing is centered on iron particles, and that snowflake foxing generally shows higher iron concentration than surrounding areas [Cain and Miller 1982, 56; 60]. This would contraindicate the use of hydrogen peroxide unless it could be shown that specific foxing did not have a high iron concentration or if iron ions could be inactivated or removed prior to bleaching.

See also PCC 19.3.1.A.

C. Calcium Hypochlorite

Gallo and Hey found that 5% solution was more effective in removing foxing stains than were 5% solutions of Chloramine-T and hydrogen peroxide (though these concentrations were not recommended for conservation use), and that reversion did not occur with sheets rinsed in alkaline water [Gallo and Hey 1988, 102]. Burgess suggests a much weaker bleaching solution (0.1 to 0.5%) and recommends that calcium hypocholorite only be used on severely stained artifacts in otherwise very good condition [burgess 1988, 22].

Calcium hypochlorite is occasionally used by conservators for stubborn foxing stains and has been found to be especially effective. It has the added advantage of being a fungicide for some species of fungi.

See also PCC 19.3.1.B.1.

D. Chloramine-T

A 2% solution was recommended [Coleman et al. 1969, 197], though this bleach has generally fallen from favour due to the difficulty in removing residues from the paper [burgess 1988, 22].

See also PCC 19.3.1.C.

E. Sodium Borohydride

This moderate to weak reducing bleach generally removes mild stains but is only capable of partially eliminating severe staining. It is commonly used by conservators in concentrations of .1 to 2%, sometimes in combination with hydrogen peroxide treatment [burgess 1988, 22].

See also PCC 19.3.3.A.

F. Natural or Artificial Light

Ultraviolet radiation in the light source, combined with moisture in the paper, will produce peroxides which could then destroy mold (if present) and bleach discolorations [Hey 1983, 342]. This is best not used with papers with conspicuous stains of heavy metals (e.g. iron, copper) or their salts or oxides. This bleaching method is commonly used by conservators for foxing stains. Some work has been done with localized light bleaching using a fiber optic light source directed only at the foxing stain to be bleached.

See also PCC 19.3.4.A and B.

[BlowUpTheMoon]

[divad]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

 

Dear Bill,

We have been discussing foxing in this forum for quite a few years now. There are many threads on the topic, which set forth all of the various causation theories. My earlier response to MCP was curt yes, but only because MCP attempted to summarize all of this in two short sentences, one incorrect on it's own alleged assertion of "fact", and the other pure conjecture (although plausible, still incorrect). It didn't warrant an explanation, because no effort was made on his part to do any research on the topic. Even much less effort in your case. He has redeemed himself (as in the other threads here). You on the other hand, provide nothing.

bestest,

David

p.s. btw . . . stick it in your arse.

[Green]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

 

Dear Bill,

We have been discussing foxing in this forum for quite a few years now. There are many threads on the topic, which set forth all of the various causation theories. My earlier response to MCP was curt yes, but only because MCP attempted to summarize all of this in two short sentences, one incorrect on it's own alleged assertion of "fact", and the other pure conjecture (although plausible, still incorrect). It didn't warrant an explanation, because no effort was made on his part to do any research on the topic. Even much less effort in your case. He has redeemed himself (as in the other threads here). You on the other hand, provide nothing.

bestest,

David

p.s. btw . . . stick it in your arse.

Mike is a master at redemption.

[divad]

This is real wordy but addresses the debate in great detail.

 

13.2.1 Causes

Despite investigations spanning almost sixty years there remains confusion and uncertainty as to what causes foxing, whether there is a single cause or multiple ones, and whether there is more than one type of foxing. There are currently three major explanations for foxing which have been proposed most often: a) fungal activity, b) metal-induced degradation, and c) multiple causes. Recently, a fourth explanation has been proposed which attempts to explain foxing stains within the context of general discoloration of paper caused by the interaction of moisture and cellulose.

 

Unfortunately, most of the published research on foxing neglects to provide accurate and complete information concerning size, shape, depth (within the sheet), or fluorescence pattern (or absence thereof) when describing foxing. In the future, it is hoped that investigators will use cain's proposed classification system (see 13.2.3), making it easier to integrate disparate research. Although researchers claim their stains had the “typical coloration characteristic of foxing,” this is fairly meaningless, as there is no way of judging the uniformity of this coloration. It is possible that researchers are finding different causes for foxing because the spots tested are different, even though they are all termed “foxing”. Hey has even suggested removing metal induced foxing from the foxing category altogether as this is “metal induced degradation”. Additionally, researchers proposing one cause over another often neglect to investigate both causes equally, lending an unstated bias to their findings of which the reader must be aware. Following is a summary of investigations and theories culled from conservation literature.

 

 

Has anyone even slugged through this yet? I mean read it, not just scan it. It's pretty poorly written. I think I'll spend some time with it when I get a chance, but as it states in it's foreword it's an inconclusive hodgepodge.

[Hero Restoration]

I admit I don't always follow what they are saying. Also allot of these article's are copy and paste from different papers on the subject. That article is 18 years old, I sure would like to read something more current.

 

All I know is when I pull a comic out of a bag that has foxing my allergies go haywire. I was able to wash out or bleach the foxing with a hypochlorite but it is also bad for the paper. I am going to try the hydroxide on a Nick Fury #2 and see if it removes it or not.

 

My guess is I am going to get inconsistent results and will avoid dealling with foxing if I can. As a collector I really hate foxing but for some reason CGC doesn't consider it a major defect and is soft on it.

[Bill Robinson]

 

Dear Bill, . . . stick it in your arse.

 

I've edited your post down to what you really wanted to say. Glad I could wind you up. I will stay out of the conversation now, unless I have something equally important as, "this is hilariously incorrect" to contribute.

 

 

 

[divad]

 

Dear Bill, . . . stick it in your arse.

 

I've edited your post down to what you really wanted to say. Glad I could wind you up. I will stay out of the conversation now, unless I have something equally important as, "this is hilariously incorrect" to contribute.

 

 

(thumbs u

[namisgr]

In the name of accuracy, the singular form of the organism that likely causes foxing is "fungus".

 

From Wikipedia, the free encyclopedia

 

Foxing is a term describing the age-related spots and browning seen on vintage paper documents such as books, postage stamps, certificates, and so forth. The name may derive from the fox-like reddish-brown color of the stains, or the rust chemical Ferric Oxide which may be involved. Paper so affected is said to be "foxed."

 

Although unsightly and a negative factor in the value of the paper item for collectors, foxing does not affect the actual integrity of the paper.

 

Foxing also occurs in biological study skins or specimens, as an effect of chemical reactions or mold on melanin.

 

Other causes of age-related paper deterioration include destruction of the lignin by sunlight and absorbed atmospheric pollution, typically causing the paper to go brown and crumble at the edges, and acid-related damage to cheap paper such as newsprint, which is manufactured without neutralising acidic contaminants.

 

 

Causes of Foxing

 

The causes of foxing are not well understood. One theory is that foxing is caused by a fungal growth on the paper. Another theory is that foxing is caused by the effect on certain papers of the oxidation of iron, copper, or other substances in the pulp or rag from which the paper was made. It is possible that multiple factors are involved. High humidity may contribute to foxing.

 

 

Repairing foxed documents

 

There are products available which were specifically designed to remove foxing. The problem with using proprietary bleaches to remove foxing is that they invariably affect the integrity of the paper and the paper has to be subsequently resized.

Using laser-based techniques to remove foxing stains from old paper is a potential solution to the problem. The use of lasers however, at longer wavelengths, is usually accompanied by side effects, since the affected area requires higher laser energies to be cleaned.

Depending on how valuable one's print or map is, one could try lightly dabbing 3% hydrogen peroxide onto the affected area using a cotton swab or cotton bud. This process is effective but one should test the paper in a less critical area first. It doesn't take much and one should not soak the spots; the hydrogen peroxide will bleach the ink just as it will bleach the foxing. Patience and repeated applications are best.

[143ksk]

 

This is not. Bill, why don't you try contributing something?

 

I am very interested in this subject as some books I recently bought have foxing on the back cover. I'm trying to learn more about the subject.

When I started reading this thread, I was shocked by how rude you were. It was nice to see your trollish behavior completely ignored and completely refuted.

Then tell us what you've learned Bill

 

Perhaps some reading David's comment thought it was spot on. I'm not sure you could mearly wash away foxing by creating an "alkaline reserve followed by a Hypochlorite solution". Good theory on the part of MPC, but it falls apart when you consider that foxing is a fungi and it does not reside mearly on the top of the paper, but actually penetrates the paper. Any type of chemical wash is going to leave those sections of the paper stained, weak, and damaged.

 

Actually, the inaccurate part was that it was fungi (which is plural by the way) and not mold. Mold is a type of fungus and the fungi listed in the article posted are molds.