CONSIDERATIONS OF THE EFFECT OF ERASERS ON COTTON FABRIC
ABSTRACT—This study examines the effect of seven dry cleaning products, several of which have been used in paper conservation, on cotton canvas. The changes in surface pH, color, brightness, and surface texture of aged and unaged samples of no. 10 cotton duck due to treatment with these products are observed. The composition of the eraser, its surface pH, and its cold extraction pH are noted, as are the quantity, color, size, and tenacity of its crumbs. Conclusions are that Pink Pearl, Kneaded Rubber, and the vinyl-based erasers examined here are the most abrasive. Pink Pearl left the greatest quantity and most tenacious crumbs. Kneaded Rubber and Pink Pearl caused the greatest darkening, reddening, and yellowing of the cotton support. The vinyl erasers gave intermediate results, while Art Gum, Tapeten Reiniger, and Absorene gave the best over all results under these experimental conditions.
MANY MODERN PAINTINGS cannot be cleaned in the traditional manner because their surfaces—either paint or fabric—are sensitive to liquids of any kind. Paintings whose surfaces include exposed areas of unprimed, raw cotton duck, such as works by Helen Frankenthaler, Kenneth Noland, Morris Louis, and Jules Olitski, present difficult cleaning problems for the conservator. The application of a swab moistened with saliva, water, or solvent could alter these surfaces by dissolving some portion of them or some material on them, thereby darkening or otherwise discoloring the area. In order to remove particulate soiling from these kinds of surfaces, painting conservators have had recourse to procedures and techniques used in other conservation fields. Among those is the use of erasers and products developed for wallpaper cleaning. However, a variety of issues need to be addressed when using erasers. These center around the composition of the eraser and its abrasive action on the textile as well as the quantity, color, size, and tenacity of the crumbs left on the surface. In addition, the effect over time of the eraser residue on the fabric's pH, color, and brightness over time needs to be considered if all the crumbs are not able or likely to be removed.
This study was designed to evaluate seven dry cleaning products and their effects on cotton duck (see table 1). Erasers may have also found use on the painted surfaces of art, but due to the complexities and varieties of paint composition, the effect of erasers on these types of layers will not be considered in this paper.
Table 1 Erasers Studied
While the paper conservation literature has recommended a variety of erasers over the past eighteen years, and investigations and analyses of varying scientific rigor have been carried out on several of these products, no research as to their effect on a canvas support has been published to my knowledge. The seven erasers chosen for this study are, for the most part, easily available and likely to be found in conservation studios. Several have been included in paper conservation studies, and, therefore, some of their properties have already been described.1
The experiment undertaken involved treating strips of unaged and preaged cotton duck with the erasers and then aging them further for different periods of time. A qualitative assessment of the abrasive effect of the erasers and of the quantity and tenacity of crumbs remaining on the surface was made. Brightness, color, and pH measurements of the textile samples were taken. Surface and cold extraction pH measurements of the unaged erasers themselves were also taken.
2 ERASER COMPOSITION AND LITERATURE REVIEW
THE SEVEN ERASERS—Absorene, Art Gum, Tapeten Reiniger, Pink Pearl, Mars Plastic, Magic Rub, and Kneaded Rubber—can be divided into three categories: starch, rubber or oil, and vinyl-based (see table 2).
Table 2 Evaluation of Erasers in Paper Conservation
Absorene is a pink, malleable material made primarily for cleaning wallpaper. Its manufacturer, Absorene Company in St. Louis, reports its ingredients to be flour, salt, water, and mineral spirits.2 A study done at the Canadian Conservation Institute (CCI) reported the composition as starch, salt (NaCI) and trace quantities of aluminum.3 Both Horton and Banks recommended Absorene for the removal of dust from books and paper objects.4 The only reservations stated were that the crumbs, when dried out, adhered to surfaces and were somewhat difficult to remove. The CCI report found that Absorene left many sticky pink particles on paper which became hard and brittle on drying.5
Art Gum was studied by McInnis, who found that it abraded paper fibers extensively, and by Pearlstein.6 Pearlstein identified it as factice, which is vegetable oil vulcanized or cross-linked with sulphur bonds. The principal method of manufacturing factice is by heating a drying oil (usually rape seed oil, although linseed, whale, and soya bean oil are also used) with 10%–30% sulphur for several hours at 150�C–170�C.7 The purpose of this process is to form cross-links between the long polymer chains of oil, and the result is a dark, elastic product. A lighter product can be made using 15% sulphur monochloride at room temperature. Other materials are frequently added to enhance its properties or speed its manufacture. Antioxidants retard degradation. Reinforcing agents (such as carbon black and, less frequently, colloidal silica) improve the tensile strength and durability. Some forms of vulcanized products are susceptible to attack by mold.8
Tapeten Reiniger appears to be a vulcanized rubber and/or vegetable oil product9 and may contain calcium carbonate, which is frequently included in rubbers as a filler and extender. (Positive microchemical results were obtained for CaCO3.) In C.V. Horie's study and literature review of conservation materials, vulcanized rubber is discussed generally: “Being tacky, the very small particles are held in fibrous material. Over time and exposure to light, the powder adheres to itself, forming a film, yellowing slightly at the same time. The rubber is almost totally insoluble in solvents.”10
Pink Pearl 101 is a pink rectangular eraser composed of factice. Pearlstein reported its components as vulcanized vegetable oil, rubber, antioxidants, softeners, pumice and coloring agents, while CCI reported its inorganic components as: silicate, magnesium, iron, aluminum, potassium, chloride, sulphur, and possibly titanium.11 The inclusion of pumice, approximately 65%–75% silicon oxide and 10%–20% aluminum oxide, is presumably to act as a filler, absorbent, and adherent for rubber products, in addition to being an abrasive. Pink Pearl was recommended by both Horton and Clapp,12 although Horton did note its abrasive quality. Pearlstein's study found that it readily abraded the surface, altered the color and texture of the test paper, and decreased its wettability. She further noted that its crumbs were the most difficult to remove and deemed it the worst eraser of those she tested.13
Mars Plastic is a white vinyl eraser, composed of poly (vinyl chloride)(PVC), a dialkyl phthalate, calcium carbonate, chloride, and possibly titanium.14 Poly (vinyl chloride) is dimensionally stable and resistant to moisture, most acids, fats, petroleum hydrocarbons, and fungus. The presence of chlorine in the organic molecule increases its density, viscosity, and chemical reactivity, but decreases its specific heat, solubility in water, and flammability. It is readily compounded into flexible or rigid forms by the addition of plasticizer, stabilizers, or fillers. The material decomposes at 148� C, and toxic hydrogen chloride fumes are evolved.15
Concern about PVC-based erasers has revolved primarily around the inclusion of plasticizers and their possible effect on the painted or printed portion of a work of art, since they are known to interact with materials in contact with them. In addition, PVC liberates hydrochloric acid as it degrades.16 CCI felt that both Mars Plastic and Magic Rub, the two PVC-based erasers examined here, contained enough calcium carbonate to neutralize at least some of the acid.17
Other concerns relate to the specific characteristics of the eraser, such as its particular abrasive material and the percentage and particle size of that material. The McInnis study found that Mars Plastic broke unsized paper fibers but did not affect sized paper. CCI felt that quantification of the damage for the purposes of comparison was not possible, but noted that low to moderate amounts of residue remained on the surface.18
Magic Rub (or Peel-off Magic Rub) is a white vinyl-based eraser. Its composition as reported by the manufacturer is 30% (weight) poly (vinyl chloride), 35% calcium carbonate filler, and 35% dioctyl phthalate as a plasticizer.19 It was recommended by Horton, Banks, Clapp, and Pearlstein. Horton noted that it did not leave harmful residue, but that it did contain abrasives and should not be used vigorously.20 Banks described it as “extremely gentle and [having] the quality of tending to pick up [its] own crumbs.”21 Pearlstein found that Magic Rub altered the surface characteristics but not the mechanical properties of paper, nor did it affect the paper's pH or wettability. It did leave some residue on the surface, however, it altered the paper the least of all the erasers she tested.22
Kneaded Rubber is made up of natural and synthetic rubbers, vulcanized vegetable oil, antioxidants, mineral oil, pumice, calcium carbonate, titanium dioxide, and carbon black.23 CCI reports its composition to be poly (isobutene), calcium carbonate, titanium, chloride, sulphur and trace amounts of magnesium, aluminum, silica, and potassium. Banks described it as being among the gentlest erasers; however, further investigation has shown it to be quite abrasive. Pearlstein noted that the use of kneaded erasers increases the wettability of the paper, and that the residual crumbs are particularly difficult to remove and are not visible to the eye.24
3.1 Sample Preparation
COTTON DUCK NO. 10 (11 � 17 threads/cm2, 0.49 grams/cm2) was cut into 1″ � 6″ strips. Three samples were cut for each experimental condition and eraser type. They were then placed in a controlled environment of 21� C and 40% relative humidity for two days. Forty-five strips were kept in the conditioning room for the duration of the experiment. These represent the unaged samples A. The others were artificially aged in a dry oven at 100� C � 5� C for seven days. The oven used was a Stabil-Therm gravity oven (Model OV-8, OV-12) manufactured by Blue M Electric Company.
After one week, the samples were removed from the oven and treated with the erasers. The A samples, except three control strips, were also treated. A fabric piece was laid on a sheet of mylar. The eraser was rubbed down the length of the sample five times.25 (Absorene was handled first in order to shape it into a wedge form.) Half of the samples were vacuumed in order to remove the eraser crumbs. The brush head of the vacuum was passed over each sample three times in the same direction as the eraser procedure. The brush head itself was vacuumed between the vacuuming of each sample. A new sheet of mylar was used for each eraser so as not to contaminate the strips. Forty-five of these were placed in the conditioning room. These were labeled B. The rest were returned to the oven for further aging. After seven days, 45 samples, C, were removed. After 14 days, the D samples were removed, and after 21 days, the E samples were removed. All samples were kept in the calibrating room when not in the oven or being examined.
3.2 Visual Examination
All the samples were examined under a binocular microscope (between 7x and 30x magnification) to assess the tenacity and quantity of crumbs as well as the abrasive quality of the eraser.
Photomicrographs were taken to record the eraser residue on the fabric and any resulting surface abrasion. These were taken using a Nikon Labophot-Pol microscope with a HFM Automatic microflex and FX-35A camera back. Photomicrographs were taken at a magnification of 40x in both normal and raking light as provided by two tensor lights. The film used was Kodak Ektachrome Tungsten, ASA 160.
3.4 Surface pH and Cold Extraction pH Measurements
Surface pH of the treated and untreated cotton samples was measured using a Fisher Acumet pH Meter, model 830, and a flat surface polymer-body combination electrode 13-639-83 with Ag/AgCl reference. The pH meter was calibrated with buffer solutions of pH 7.0 and pH 4.0, in that order, before each use.26 A droplet of distilled water (pH 5.84–pH 6.84) was placed on the sample. After one minute, the electrode was placed on the droplet. A reading was taken after four minutes. The electrode was rinsed in distilled water for one minute and wiped with Kimwipes between each reading.27
Surface pH measurements were also made on the erasers. A droplet of water (pH 6.98) was placed on the eraser and allowed to stand for one minute before placing the electrode in contact with the eraser. The reading was taken after the two had been in contact for four minutes. Three readings were taken of each eraser.
Cold extraction pH measurements were made of the erasers following the method suggested in TAPPI Standard T509 su-68. The pH of distilled water fell between 6.2 and 7.3 as needed. The electrode was calibrated with pH 4 buffer solution followed by pH 7 solution. Each eraser was grated. Distilled water was added to 1 gram of grounds to bring the volume to 70 ml. The reading was taken after the mixture had been allowed to stand for one hour. Three measurements were taken of each solution.
3.5 Tristimulus Values and Brightness Measurements
Tristimulus values and brightness were measured with a Macbeth 1500/PLUS Quick Key Color Measurement System, which consists of a Color-Eye optical sensor (spectrophotometer), and an IBM personal computer and Quick Key software. The parameters chosen for the measurements were as follows: CIELAB color formula; 2 degree observer; north sky daylight as both primary and secondary illuminants; reflection color-eye mode; ultraviolet energy included; spectral component excluded.28 Three measurements were made and averaged for each data point.29
These measurements are most frequently made on surfaces that are a great deal more uniform than woven textiles. In order to verify that the results obtained were not simply due to the angle at which the textile had been placed in the instrument, a series of readings were taken of sample 1OA: five measurements were made with the sample in the horizontal direction, five in the vertical direction, and five diagonally.
4.1 Visual Examination
4.1.1 Abrasion or Alteration of Cotton Surface
AFTER HAVING BEEN AGED for seven days the samples did not appear to have been abraded any more than before. That is, the abrasion of A samples was indistinguishable from that on B, C, D or E samples (see table 3).
Table 3 Alteration/Abrasion Of Cotton Duck and Quantity of Eraser Residue
- Absorene: The fibers protruding from the yarn are redirected so that they are preferentially aligned in the direction of eraser and vacuum use.
- Art Gum: As with Absorene.
- Tapeten Reiniger: As with Absorene.
- Pink Pearl: The fibers are redirected and some pulled out of the yarn. Crumbs are visible twisted and wrapped in cotton fibers.
- Mars Plastic: as with Pink Pearl.
- Magic Rub: as with Pink Pearl.
- Kneaded Rubber: The fibers are altered in direction and some appear to have been pulled out of the yarn.
The severity of fiber redirection is clearly a function of the pressure applied during eraser use and of the firmness and density of the eraser itself.
4.2 Characterization of Crumbs
The quantity of crumbs was defined in the following manner: none; few (1 to 3 crumbs per cotton strip); moderate (4 to 6 crumbs); many (7 to 20); and abundant (21 or more). Tenacity was defined in the following manner: not tenacious (95%–100% crumbs had been removed after vacuuming); slightly tenacious (25% or fewer crumbs remained), and tenacious (75% or more crumbs remained). Other categories were not found to be necessary.
Absorene: The vacuumed samples have many crumbs, while the unvacuumed samples have an abundant quantity of crumbs. These particles are generally small, pale pink, and invisible to the unaided eye; the larger ones are darker in color and more easily seen. As the textile ages, they became darker and yellower. The particles tend to be in the fibers that stand proud of the weave, except if too much pressure has been used in applying the eraser. In that case, the residue is enmeshed in the weave itself. Crumbs on samples of all ages were easily disengaged from the fibers by several passes of a bristle brush. (The brushing action realigned the fibers but did not appear to alter the cotton in any other way.)
Art Gum: Many crumbs are left on the sample even after vacuuming. Without vacuuming, the crumbs are abundant. They are small, pale yellow, and difficult to see, even with magnification. With aging, they darken. The crumbs remaining on the surface after vacuuming tend to be deep in the weave of the textile rather than caught in the protruding fibers. However, they are easily removed by further vacuuming or bushing.
Tapeten Reiniger: There are a moderate number of crumbs on the samples that had been vacuumed and abundant crumbs on those that had not. The particles are very small and pale when fresh but darken to a deep orange upon aging. They are invisible to the eye unless present in large numbers. A bristle brush easily dislodges them; however, they can readily be redeposited if they are not removed from the brush hairs.
Pink Pearl: There are abundant small pink crumbs on the vacuumed samples. They become darker and yellower with age but are generally invisible to the eye. On the unvacuumed samples, larger curls of eraser residue are visible. Crumbs are visible both deep in the weave and in the fibers. They are tenacious and are not all removed even with aggressive brushing.
Mars Plastic: Few particles are visible on the vacuumed strips. Abundant, very tiny white crumbs are visible on the unvacuumed samples. They are mostly in the weave and invisible to the eye. Persistent brushing is necessary to remove them due to their quantity and location.
Magic Rub: There is a moderate number of crumbs on the vacuumed samples. These are small, rounded, white particles that are invisible to the eye. They do not discolor upon ageing. Unvacuumed samples contain larger particles that are caught in the fibers and slightly resistant to removal by brushing.
Kneaded Rubber: No crumbs are visible on the vacuumed strips; many are visible on the unvacuumed ones. The tiny transparent or white crumbs are invisible to the eye. They are mostly located in the weave and are easily brushed away.
4.3 Surface pH and Cold Extraction pH
No conclusions from the surface pH readings of the treated and untreated samples could be drawn as the results were not deemed scientifically significant. The pH measure for the textile fluctuated with the slightest change in the pH of the distilled water. In addition, the reading was dependent upon whether or not the droplet of water came into contact with and solubilized an eraser crumb. The results, therefore, have not been described here.
Surface pH measurements were taken of the erasers themselves. The results are shown in table 4. Cold extraction pH readings taken of the eraser crumbs are also shown.30
Table 4 Surface pH and Cold Extraction pH of Erasers
4.4 Tristimulus Values
Tristimulus values were obtained for each sample. The values correspond to the following: L = lightness (100) to darkness (0); a = red-green difference, with +a indicating redness while −a indicates greenness; b = blue-yellow difference, with +b indicating yellowness while −b indicates blueness. The values for a and b are zero for neutral colors such as gray, black, or white; however, their values rise as the color becomes more chromatic or saturated (see table 5).
Table 5 Tristimulus Values
Both primary and secondary illuminants were north sky daylight. In order to assess the effect of this choice as opposed to incandescent or cool white fluorescent, measurements were made on the same sample (10A) under each lighting condition. The results (see table 6), show that the illuminants affect the “L,” “a,” and “b” values in the following manner: Northern daylight gives the darkest, greenest, and least yellow values. Incandescent gives the middle value for lightness of these illuminants, the reddest and the middle value for yellowness. Cool white fluorescent gives the darkest and yellowest values as well as a neutral zone value for red-green. In table 7, the erasers are arranged in descending order from lightness to darkness, from −a to +a and from −b to +b to assess easily the effect of the erasers in relation to each other.
Table 6 Effect of Illuminants on Untreated Cotton
Table 7 Relative Tristimulus Values for E Samples
4.5 Brightness Measurements
Brightness measurements correspond to the light reflected from the sample at 457nm. Readings were taken for sample 10A in three different positions (horizontal, vertical, and diagonal) to determine the effect of weave direction on the brightness measurement. The change in value due to the direction of the weave was found to be insignificant, especially when compared to that caused by the eraser treatment.
Brightness values for the samples are shown in table 8. Table 9 lists the erasers in order, from those having the least to those having the greatest dulling effect on the brightness of the cotton sample.
Table 8 Brightness Measurements
Table 9 Realtive Brightness of Samples
The overall effect on the brightness of the cotton from B to E aging periods and in vacuumed and unvacuumed states was calculated by giving each eraser a ranking under each experimental condition. For example, in the B, unvacuumed state, the erasers are ranked as follows: Tapeten Reiniger (1), Art Gum (2), Absorene (3), Mars Plastic (4), Magic Rub (5), Pink Pearl (6), and Kneaded Rubber (7) (see table 9). Similar lists were compiled for each experimental variable, and the numbers ascribed to an individual eraser were added. The overall ranking appears in the far right column: The smallest number shows the eraser with the least dulling effect, while the highest number represents that product with the greatest effect.
5.1 Visual Examination
THE QUANTITY AND HENCE THE EFFECT of the eraser crumbs left on the cotton is an important factor especially when they are tenacious and cannot be thoroughly removed. The most tenacious crumbs proved to be those of Pink Pearl. The vinyl eraser crumbs were only slightly better. Others were easily removed provided the eraser had not initially been used with excessive force. (This is especially true of Absorene.)
The quantity of crumbs is a particular concern when they are invisible to the eye and therefore appear to have been removed without actually being so. Even after vacuuming, many crumbs were left by Absorene, Art Gum, and Pink Pearl, while few or none were left by Mars Plastic and Kneaded Rubber. However, these last two—along with Magic Rub and Pink Pearl—altered the surface the most. Absorene, Tapeten Reiniger and Art Gum altered it the least.
5.2 Surface pH and Cold Extraction pH
Results from the surface pH and cold extraction pH measurements of the erasers show a broad range: Absorene is the most acidic, while Art Gum is the most alkaline. However, the differences in the eraser pH did not have a measurable effect on the pH of the cotton samples in this experiment.
Because of the discrepancy between the surface pH and the cold extraction pH values obtained for Art Gum, a small experiment was undertaken. The eraser was cut along the short axis into four parts. The surface pH of each interior surface and of the exterior surfaces was taken. The results showed a large variation between the pH of interior and exterior surfaces. Readings taken sixteen days later on the same eraser showed a decrease for the interior pH values. The general explanation for this must be that acidic degradation products from as the eraser oxidizes, however, the specific reaction is unclear.
5.3 Tristimulus Values
The tristimulus values show that in most values, L, a, and b, Art Gum, Absorene, and Tapeten Reiniger consistently gave the best results, affecting the lightness, redness, and yellowness the least even after ageing. Pink Pearl and Kneaded Rubber, on the other hand, gave the worst results, causing the greatest change in these values.
Pink Pearl gave an especially high value for redness due to the eraser color and the quantity of residue left on the cotton surface. The vinyl erasers gave moderate values in each category.
5.4 Brightness Measurements
Art Gum, Absorene and Tapeten Reiniger affect the brightness of the cotton the least. Kneaded Rubber and Pink Pearl have the greatest and most immediate effect; the values have already dropped by 2 or 3 units, when compared to the control sample, in the B stage of aging and continued to dull the fabric as the aging progressed.
THE REMOVAL OF PARTICULATE SOIL from a cotton surface is not always fully successful when done with a brush, vacuum, or compressed air. Erasers are often the treatment procedure next considered. In choosing an eraser, however, care should be taken to address its hardness in relation to the brittleness of fabric. In addition, the compatibility of the eraser composition with the textile and the design layer, as well as the eraser's effect on the fibers and the weave, must be considered. Inclusions, such as sulphur in the rubber-based erasers, and a dialkyl phthalate in the vinyl-based erasers, pose particular concern. Further research is certainly warranted in these areas.
The technique of using the eraser can be varied in order to achieve different results. Scrubbing the surface will raise the nap, leave more residue, and remove more soil, as opposed to gently pulling or rolling the eraser across the surface. Both the techniques of use and the choice of eraser are therefore essential in the success of the treatment, as is the thorough removal of the residue.
Table 10 presents a general summary of the test results from this experiment. The surface pH measurements of the cotton support were not deemed significant; the effect of the distilled water used to take the reading appeared to have a greater effect on the data than did the eraser crumbs themselves. The surface pH and cold extraction pH of the erasers are labeled unsatisfactory in the final tally if the reading fell below pH 6 or rose above pH 9. These extremes are considered potentially unsafe for the cellulose support.
Table 10 Summary of Results
Tristimulus and brightness values are summarized for both vacuumed and unvacuumed samples at the E stage of aging. In both tests, Kneaded Rubber and Pink Pearl are unsatisfactory: they cause the greatest darkening (low L value), reddening (+a value), and yellowing (+b value) of the textile. Absorene, Tapeten Reiniger, and Art Gum altered the cotton the least, while the vinyl erasers altered it a moderate amount. The results of the brightness measurements closely follow those of the tristimulus tests.
Each treatment situation involves a different set of limitations and criteria, and it is hoped that the results of this study will aid in that decision-making process. While it is not possible to wholeheartedly endorse any single product, one may conclude from these tests that erasers such as Kneaded Rubber and Pink Pearl may be considered inappropriate for use in conservation.
THE AUTHOR GRATEFULLY ACKNOWLEDGES Dr. Norbert Baer for his advice and guidance throughout this project, and extends warm thanks to Eneida Parreira, a fellow student at the Conservation Center, Institute of Fine Arts, New York University, for her work and enthusiasm during the initial phases of this experiment.
1. Paul Banks, “Paper Cleaning,” Restaurateur 1, no. 1 (1969): 52–66; Anne F. Clapp, Curatorial Care of Works of Art on Paper (Oberlin, Ohio: Intermuseum Conservation Laboratory, 1978), 59–61; Carolyn Horton, Cleaning and Preserving Bindings and Related Materials (Chicago: Conservation of Library Materials, 1969), 32–34, 62–64; Kerry McInnis, “Two Studies in Paper Conservation Practice,” ICCM Bulletin, 6, no. 2 (June 1980): 43–53; Elizabeth Moffat and Marilyn Laver, “Erasers and Related Dry Cleaning Materials” (Unpublished Canadian Conservation Institute Analytical Report, ARS No. 1738, File No. 7034-20-3, October 20, 1981), hereafter cited as CCI; Ellen Pearlstein, D. Cabelli, A. King, and N. Indictor, “The Effect of Eraser Treatment on Paper,” JAIC 22(1982): 1–12.
2. Verbal communication with the manufacturer, March and April 1987.
3. CCI, 5.
4. Horton, 33; Banks, 53.
5. CCI, 3–4.
6. McInnis, passim; Pearlstein, et al., 2.
7. W. J. Roff, Handbook of Common Polymers (Cleveland: CRC Press, 1971), 238–239.
8. Paul F. Hamlyn, “Microbiological Deterioration of Textiles,” Textiles 12, no. 3 (1983): 74–75.
9. Analysis of each eraser by means of pyrolysis gas chromatography was carried out by Alexander Shedrinsky at the Conservation Center, Institute of Fine Arts, New York University. Tapeten Reininger gave a trace similar to that of Pink Pearl and Art Gum, showing that it, too, is factice-based. Microchemical spot tests showed the presence of calcium carbonate.
10. C. V. Horie, Materials for Conservation (Boston: Butterworth, 1987), 91.
11. Pearlstein et al.,2, CCI, 2. Analyses were performed by X-ray primary emission spectroscopy in the scanning electron microscope and by IR spectroscopy. Chloride was detected with a specific ion electrode.
12. Horton, 33; Clapp, 78.
13. Kneaded Rubber, Pink Pearl, Art Gum, Opaline, and Magic Rub were tested.
14. CCI, 5.
15. G. G. Hawley, The Condensed Chemical Dictionary, 10th ed. (New York: Van Nostrand Reinhold, 1981), 841.
16. Banks, 53.
17. CCI, 7.
18. McInnis, 45; CCI, 4–6.
19. Pearlstein et al., 20.
20. Horton, 33.
21. Banks, 52.
22. Pearlstein et al.
23. Pearlstein et al., 2.
24. Pearlstein et al., 11.
25. The eraser was held against the cotton surface with gentle but firm pressure. However, without a more quantitative means of measuring and reproducing this force, this procedure represents, in all probability, the largest source of variables in the experiment.Because of concern regarding the use of mylar as a surface on which to erase the fabric strips, this portion of the experiment was repeated using both a formica and blotter paper surface. Mylar has a tendency to build up static charge, which may affect the quantity and/or tenacity of the eraser crumbs on the fabric. In this case, the results of the erasing procedure carried out on the other surfaces correlates with those from the mylar-supported strips, however, in the future mylar should be avoided.
26. The conditioning of the electrode was carried out as per A. Joel, N. Indictor, and N. Baer's recommendations, that is, “conditioning is optimum when the electrode is immersed in a buffer of pH near that of the test reading of the paper surface.” A. Joel, N. Indicator, J. F. Hanlan, and N. S. Baer, “Measurements and Significance of pH in Paper Conservation,” IIC-AG 12, no. 2(1972), 124.
27. This procedure was carried out by Pearlstein et al. (7) and is recommended by G. Shugar, R. Shugar, and L. Bauman in Chemical Technicians' Ready Reference Handbook (New York: McGraw Hill, 1973), 266. Three readings were taken of each of the following samples: 10A-E, 21D, 22B-D, 32B-D, 41A-E, 42A-E, 52B-E, 62B-E, 72B-E, and 829-F. The practice of triple readings was abandoned when it was noted that the pH of the cotton did not change in relation to the particular eraser used but rather was affected by the change in pH of the distilled water used to take the reading. One reading was taken for each of the remaining sample categories, that is, 21A, 21B, 21C, etc.
28. For matte surfaces, either setting (spectral inclusion or exclusion) can be used since the results are almost identical. 500/Plus Quick Key Color Measurement System Operator's Manual 1st ed. (New York: Macbeth, 1985). 6–5.
29. Tristimulus and brightness values were not obtained for most of the A samples. Their appearance was not perceptively different from that of the control samples, which was confirmed by the Macbeth readings for Art Gum A samples: these fall within the standard deviation of the A control samples.
30. The mixture of crumbs and water in covered beakers was inadvertently left to stand after the cold extraction pH readings had been taken. Within a week, the Absorene beaker had grown a layer of white fluffy mold and the water had turned a turbid brown. The Pink Pearl mixture had also begun to grow mold: numerous discrete, dark brown, branched particles were visible on the water's surface.