Effects of Desiccation on Degraded Binder Extraction in Magnetic Audio Tape
Norris, Sarah, ARSC Journal
As some types of magnetic audio tape age, they develop a set of problems known as sticky shed syndrome. During playback, affected tapes can produce a squealing sound and leave behind a gummy residue at contact points on the tape machine. This residue accrues and slows the linear speed of the tape, making playback difficult and sometimes impossible. Segments of the magnetic media can detach from the tape, removing recorded information and often reducing sound quality. Sticky shed syndrome generally affects tape manufactured from the mid-1970s to the mid-1980s, and it is a serious concern for the custodians of historical audio collections. Reels of tape cannot simply sit idle on a shelf; they must function in playback at least once for their content to he meaningfully retrieved.
One solution developed by audio technicians to treat sticky shed syndrome is baking. In this treatment, affected tape is exposed to temperatures of 125-135" Fahrenheit for between one and eight hours. This procedure is supported by one patent (Medeiros et al., 1993) and much anecdotal evidence (Norris, 2007), but its effects are temporary, usually lessening the symptoms of sticky shed syndrome for just several weeks. This time provides an opportunity in which to capture one analog playback as a digital recording, which can then function as source material for future use. Baking has been a powerful tool for audio specialists, but it is not effective for all tapes, and there is growing concern that required baking times are increasing as tapes continue to age (Hess, 2008). The future effectiveness and reliability of the treatment is unknown.
While the baking treatment has allowed many sticky shed tapes to be digitally transferred, little discussion has been devoted to the possible negative consequences of placing historical audio artifacts in an oven. The short- and long-term effects of elevated temperature on magnetic audio tape's components, including the magnetic coating. substrate, and back coating, have not been thoroughly studied. Baking is an inherently aggressive treatment that shares much in common with accelerated aging studies, and accordingly risks exposing tapes to activation energies required to initiate degradation mechanisms. Although it is the only commonly accepted technique for remedying sticky shed, the baking treatment may achieve today's playback at an unknown future cost.
The strong need for testing and study of sticky shed syndrome, the baking treatment, and magnetic tape in general is complicated by the formidable uncertainties of provenance that riddle the audio field. Specific chemical formulations of tape components were often considered proprietary and not disclosed by the manufacturers. As a result, current audio specialists lack key knowledge about the composition of their materials. Tape makers and their suppliers frequently made slight changes in their formulations while maintaining the same product identification. Sometimes formulation changes occurred within a single production run, and sometimes product naming and numbering schemes were inconsistent (Eilers, 2000). Today, understanding the fundamentals of these materials is becoming an increasingly daunting task as tape manufacturers cease production and technical support for the format dwindles.
Further, it is often impossible to make a visual identification of the manufacturer or type of tape. The tape itself usually bears no distinguishing mark. Reels and boxes may carry those marks, hut after years of practical use, these accompanying materials are seldom original. As a result, audio specialists often work with tape of completely unknown origins.
These difficulties of provenance create a serious handicap for controlled research in the audio field. Accordingly, audio professionals have been forced to develop working solutions, like baking, without significant scientific foundations. Further research into these topics could help to standardize practices and establish treatment solutions that are more strongly rooted in conservation ethics.
As audio preservation matures in the archival environment, inherent tensions are apparent between the preservation philosophies of the audio field and the conservation field. Audio specialists generally focus on an item's content more than its physical artifact. Conservators, on the other hand, often focus on unique physical artifacts and view content as a less separable commodity. In this study, a synthesis of the two views is sought. Unlike baking, an ideal sticky shed treatment would improve retrieval of recorded content without risking additional harm to the physical audio artifact.
Tape Structure, Degradation & Treatment
The magnetic audio tape in this study has the following structure. Each component has a specific function in the recording and playback of sound.
Media particles can consist of [Fe.sub.2][O.sub.3] or Cr[O.sub.2]. These particles capture recorded sound in the form of magnetic polarization during recording. During playback, that magnetic charge is read and reproduced as audible sound waves.
The binder is polyester polyurethane, which serves as a glue to hold the media in a cohesive layer attached to the flexible substrate. To prepare the tape's coating layer, binder and media particles are mixed together with a solvent and cast onto the substrate. When the solvent evaporates, a dry, magnetic pigment-rich coating is left behind (Bradshaw & Bhushan, 1984). Polyester polyurethane binder became prevalent in the early 1970s because it allowed a high density of magnetic particles, but its long-term stability has proved problematic.
[FIGURE 1 OMITTED]
The substrate layer in the tapes in this study is polyester terephthalate, or PET. PET's use began in 1953 (Hess, 2008); other historical substrates have included acetate, paper, and PVC. The substrate provides the strength and flexibility required for the tape to withstand tensile forces imparted by the tape machine.
The back coating is optional, and consists of carbon black embedded in what is usually the same binder used in the magnetic coating. The rough surface of the back coating facilitates winding and unwinding by preventing the smooth tape surfaces from blocking, or sticking together. It produces a smoother wind by allowing entrapped air between the windings to easily escape. The conductive carbon black also helps manage the tape's surface conductivity.
Additionally, tapes can include a lubricant, not shown in Fig. 1. Lubricants can consist of long chain hydrocarbons or fatty acid esters, and were once derived from alkanes like whale oil and shark oil.
Two main theories attempt to explain the degradation mechanism at work in sticky shed syndrome. One idea is that sticky shed is caused by degradation of tape's back coating layer, and playability can he restored by stripping that layer off the tape (Richardson, 2006). The other idea is the most established theory, and the one that forms the basis of this study. This idea states that as tape ages, its binder layer undergoes hydrolysis.
The hydrolysis theory stems from several seminal audio tape studies conducted in the late 1970s and early 1980s (Cuddihy, 1976; Bertram & Cuddihy, 1982; Cuddihy, 1983). The polyester polyurethane binder used in audio tape is formed by a reversible chemical reaction, esterilication. In esterification, a carboxylic acid and an alcohol react to form an ester, with elimination of water. Hydrolysis is the reverse of esterification. In this reaction, water breaks the ester linkages to reform the carboxylic acid and alcohol. In the hydrolysis of polyester polymers, not all the ester linkages are broken. Instead, the reaction produces smaller molecule segments with both acid and alcohol ends (Bradshaw & Bhushan, 1984).
[FIGURE 2 OMITTED]
Each time chain scission occurs at one of the binder's ester groups, another acid group is produced, creating a simultaneous rise in acidity and drop in molecular weight (Brown et al., 1980). A drop in the binder's molecular weight makes the coating more susceptible to mechanical failure, or shedding. Further, low molecular weight binder particles are able to migrate to the surface of the tape, creating sticky residue (Bradshaw et al., 1986). In this way, binder hydrolysis causes both of the namesake symptoms of sticky shed syndrome. Mass spectrometry has shown polyester fragments to be the primary component of sticky tape residue (Bradshaw et al., 1986).
How does the baking treatment impact hydrolysis and binder degradation? One study says that baking reverses hydrolysis, thus re-forming ester linkages and reassembling binder molecules (Bertram & Cuddihy, 1982). The elevated temperature and relatively low relative humidity, RH, inside a hot oven drive excess moisture from the tape, creating an environment in which binder hydrolysis can be reversed, stickiness reduced, and playback performance improved. These effects are understood to he temporary because hydrolysis resumes after baking, presumably proceeding for several weeks until a critical mass of binder re-degrades and the tape again becomes unmanageably sticky. High temperature and low RH work together to reduce the tape's water content through processes of evaporation and equilibrium. By this reasoning, temperature and RH are complimentary tools that could conceivably be employed separately to achieve some treatment benefits.
However, conflicting research says that the baking treatment does not actually reverse hydrolysis (Bradshaw & Bhushan, 1984). Instead, baking causes the degraded, hydrolyzed binder particles and media particles to be held in better cohesion within the tape's coating layer. Elevating the temperature softens the hinder and allows greater mobility of binder particles within the coating slurry. Once mobilized, hard segments of the polyester polyurethane binder molecules are more likely to form hydrogen bonds with the magnetic media particles. Reducing the RH minimizes interference with this reaction by reducing the amount of available atmospheric water molecules that might occupy hydrogen bonding sites on the media, thus allowing more hard segments of the binder to bond with the media. Though ester linkages are not restored, the coating becomes more cohesive and less prone to mechanical failure (R. Bradshaw, personal communication, 28 March 2010). By this reasoning, temperature and RH are both integral tools to the success of the baking treatment.
Within the world of libraries and archives, the careful maintenance of relatively low RH is generally recognized as a reliable preservation strategy, and low-RH storage conditions are specifically recommended for audio materials (St-Laurent, 1991; Van Bogart, 1995). However, elevated temperatures, in either long-term storage or short-term treatment, raise serious concerns about unintended physical damage that could affect the lifespan of archival materials. In order to weigh the risks and benefits of the baking treatment, the necessity of both elevated temperature and reduced RH must be evaluated.
The goal of this study was to investigate a potential alternative treatment to baking that would reduce RH without raising temperature. The chosen method was exposure to a desiccant. This methodology allowed the use of materials and concepts already familiar within library and archives settings. The test method was constructed to reduce the overall risk of the treatment by employing a less aggressive strategy intended to impact the tape as gently as possible.
Rationale: In order to test the effects of desiccation, desiccation chambers were constructed using Rhapid Gel, a product made by Art Preservation Services and used to control RH in museum cases. A Rhapid Gel sheet consists of small beads of silica gel (Si[O.sub.2]) sandwiched between two sheets of woven polyester. Each desiccant chamber was constructed with two sheets of Rhapid Gel enclosed in two sheets of Mylar, the outer edges sealed with pressure-sensitive tape. Audio tape samples were enclosed in the chamber between the two Rhapid Gel sheets. One desiccant chamber was constructed for each tape type tested, making two total. Both chambers were conditioned to 25% RH by heating the Rhapid Gel sheets in a microwave, as suggested by the product vendor.
To evaluate the amount of degraded binder in a sample, the acetone extraction method was used. This process was established in early tape research (Bertram & Cuddihy, 1982; Cuddihy, 1983) and more recently standardized in a report by the Image Permanence Institute (IPI) (Bigourdan et al., 2006). The IPI standard served as the basis for the methodology used in this study. In acetone extraction testing, tape samples are submerged in a solvent bath of acetone, which removes degraded binder material.
The reasoning behind acetone extraction is as follows: during degradation, hydrolysis breaks chains of polyester polyurethane binder into smaller ester and urethane segments. Degraded, low molecular weight ester segments are soluble in acetone, while less-degraded, higher molecular weight urethane segments remain insoluble. By weighing the tape sample before and after acetone extraction, the calculated percent mass change indicates the quantity of hydrolyzed binder present, and thus indicates the severity of the binder's degradation. Infrared analysis has shown acetone extract to consist nearly entirely of binder material, with no material extracted from the non-binder components of the tape (Bertram & Cuddihy, 1982). This notion may be problematic given murky knowledge of many tapes' material construction and the potential presence of degradation components that are not yet understood. It is hoped that if the acetone affects the media, substrate, or back coating, it does so regularly across the sample group.
In this study, varying hours of a desiccation process were paired with the acetone extraction test. This was intended to examine what effect desiccation might have on the amount of degraded binder present in the samples as reflected in the samples' percent weight change. The samples were grouped, weighed, placed in the desiccation chamber for specified periods of time, extracted in acetone, and weighed again. A successful treatment was expected to yield an un-desiccated control group with a relatively large percent mass loss, and test groups with smaller and smaller percent mass losses for each increase in desiccation time. In other words, more desiccation was expected to produce less degraded material.
The idea of using photographs taken through a microscope to evaluate tape degradation is explored by Richardson (Richardson, 2006). Photomicroscopy was included in this test's procedure in an attempt to pair visual data with numerical mass data.
Tape Collection; Reels of sticky shed tape were solicited on the Association for Recorded Sound Collections Discussion List (ARSCLIST). Several different brands and types of tape were donated. Those that provided a useful sample size were Ampex 456 and Shamrock 041, both 7-inch reels of 1/4-wide tape, and both PET-based tapes with [Fe.sub.2][O.sub.3] media. The Ampex tape base film was 1.5 mils thick, or 1.5/1,000 of an inch; the Shamrock was 1 mil thick, or 1/1,000 of an inch. The Ampex tape was back-coated; the Shamrock was not.
As is often the case in audio preservation, the remaining facts about these tapes' provenance are somewhat uncertain. Ampex 456 was manufactured and widely used as a high-quality mastering tape, but has since become one of the most likely tapes to develop sticky shed syndrome. The Ampex tape's donor indicated its manufacture was relatively recent, most likely in the mid-1990s, making it somewhat newer than the highest-risk sticky shed group. Eight donated reels remained shrink-wrapped in their original boxes, and had recently been stored in controlled, low-temperature, low-RH conditions, the exact values of which are unknown. Upon visual inspection, the tapes all appeared stable, shedding little to no media or back coating. The donor indicated that Ampex 456 tape typically develops sticky shed symptoms and typically responds to baking, but that this batch might still be in good condition due to its age and storage history.
The Shamrock tape's age and storage conditions are unknown. Anecdotal evidence indicates that Shamrock was made by the Irish tape company, which was purchased by Ampex in the early 1960s. Shamrock tape is reported to be a relatively low-quality tape, notoriously variable in its manufacture and unreliable during operation. After Ampex purchased Irish, Shamrock tape likely consisted of Ampex 456 seconds, those tapes manufactured as Ampex 456 that did not meet performance standards. Five donated reels arrived for this study, each in the same type of storage box, which appeared to be original. Upon visual inspection, the tapes all appeared to be shedding a similar amount of small media flakes. These observations may imply that the five Shamrock reels share a similar age and recent storage history, though no supporting documents are available. The donor indicated that Shamrock 041 tape typically develops sticky shed symptoms, but does not typically respond to baking.
Creating Samples and Test Groups: For each tape type. 100 samples were cut, each 72 inches in length. Within tape types, equal numbers of samples were cut from the outer ends of each available reel. The reel number and reel position of each sample were noted and linked with the unique sample number on a spreadsheet. Standard labeling implements for the samples such as markers or pens were avoided due to possible reaction with the acetone hath. Instead, gentle impressions were placed on the end of the samples with the tip of an awl, A Braille code was used to create the impressions. Braille is an efficient code that requires a maximum of eight impressions to express one number, thus minimizing disruption of the media and back coating.
IPI standards call for the tape samples to be accordion-folded for easier insertion into the acetone bath. However, preliminary testing demonstrated that accordion-folding caused significant media loss, especially in the fragile Shamrock tape. To ease handling of the long, springy samples without losing media, the samples were loosely rolled around a 1.5- inch plastic core. The core was then removed, and each roll was secured with a loosely tied two-inch segment of nylon cord. Nylon was chosen for its low degree of hygroscopicity and its insolubility in acetone (Mark, 2003). Each sample was processed in this manner, resulting in 100 labeled, rolled, tied samples for each tape type.
The samples were then randomly selected to create four test groups for each of the two tape types, A total of eight test groups contained 25 samples each. For each tape type, Group A was the control, with no exposure to the desiccant. Group B was exposed to the desiccant for two hours; Group C for four hours; and Group D for eight hours. Nitrile gloves were used to handle the samples at all times.
Procedure: Samples were acclimated to the lab surroundings at approximately 70[degrees] Fahrenheit and 55% RH for one hour. Samples were then placed on a jig and photomicrographed under 4.Ox magnification using a Leica S6D microscope with a Leica 10445930 lens, a Leica DFC320 camera, and a Leica KL 1500LCD light set at intensity ID. The images were captured in Adobe Photoshop on a Dell GX280 computer. The jig positioned each sample under the camera lens six inches away from its labeled end.
[FIGURE 3 OMITTED]
Samples were weighed on a Mettler AE 163 balance. Group A, the control, then went directly into acetone extraction. Each sample was submerged in 30 mL of acetone in a 50 mL glass beaker for 30 minutes at room temperature, as per IPI standards (Bigourdan et al., 2006). The samples were then removed from the bath, gently rinsed with acetone, and placed on filter paper to dry for 30 minutes. Each sample was then weighed again and photomicrographed again on the jig.
Groups B, C, and D underwent the same procedure, with the addition of time in the desiccation chamber. Each sample acclimated to the room for one hour, was photomicrographed, and weighed. Group B then entered the desiccation chamber for two hours, Group C for four hours, and Group D for eight hours. After desiccation, all groups immediately underwent acetone extraction, drying, weighing, and photomicroscopy, as described above. Nitrile gloves were used to handle the samples at all times.
Pull results are summarized in Figs. 4 & 5 (pp. 191,192), Recall that samples were cut successively from the outside of multiple reels and numbered sequentially, as reflected in the "Reel" and "Position" columns.
Tape treated for progressively longer amounts of time was expected to show progressively smaller percent mass losses due to the reversal of binder degradation. When summarized across the test groups, these results would yield a summary graph with negative data points, a roughly linear relationship, and a positive slope. Actual results for the test groups are shown in Figs. 6 & 7 (p. 194). In addition to these graphs' unexpected shape, note the gain in mass for some sample groups.
Mean percent mass change was evaluated for each tape reel and for each sample position in the reels. Results are shown in Figs. 8 & 9 (p.196);
The photomicrographs taken before and after treatment revealed no significant trends in the treatment's results. Overall, photomicrographs of the Ampex 456 tape looked very similar, showing uniform coatings of dark brown media particles. Photomicrographs of the Shamrock 041 tape looked different from one another, some showing rough surfaces and losses (examples are reproduced in Fig. 10, p.196). These images supported initial visual observations about the relative stability of the Ampex tape and the relative instability of the Shamrock tape.
Standard Deviation; The standard deviation within the mean percent mass change for each sample group was calculated in order to examine the regularity of the data. For the Ampex 456 tape, the standard deviations for test groups A, B, C, and D were, respectively, 0.4788, 0.3920, 0.4987, and 0.3005. For the Shamrock 041 tape, the standard deviations for test groups A, B, C, and D were, again respectively, 2.9782, 1.5356, 1.9911, and 1.6044. These figures show that there were much wider differences in desiccation results for the Shamrock tape than the Ampex tape.
Standard deviation was also calculated for the mean percent mass changes evaluated by reel and sample position in the reel. For the Ampex 456 tape, the standard deviation between the reels was 0.2267, and between the sample positions was 0.2157. For the Shamrock 041 tape, the standard deviation between the reels was 1.6261, and between the sample positions was 0.7751, Once again, the Shamrock data exhibited greater variance than the Ampex data, with the largest variance occurring between reels of Shamrock tape. Overall, standard deviations tended to be higher when the data was evaluated by desiccation time (test group) than when it was evaluated by reel or sample position.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
Statistical Significance: In order to evaluate the statistical differences between test groups, a single factor analysis of variance test, or ANOVA, was conducted (Vaughan, 2001). For the Ampex 456 tape, the F value of 83.6501 exceeded the critical value for F, 2.6994. Therefore, the null hypothesis was rejected and a difference was found between the sample groups. Tukey's HSD test was then used to evaluate the degree of difference between each group. Statistical differences were found to exist between all test groups except A (the control) and B (two hours' desiccation).
For the Shamrock 041 tape, the F value of 9.0784 exceeded the critical value for F, 2.6993, so a difference was again found between the sample groups. Tukey's HSD test revealed that statistical differences exist between Groups A and C (control and four hours' desiccation), A and D (control and eight hours' desiccation), B and C (two hours' and four hours' desiccation), and B and D (two hours' and eight hours' desiccation).
As noted in the Test Results section above, the results from the test groups for both types of tape show two surprising results. First, several sample groups show a mean percent mass gain, rather than the expected mean percent mass loss. Second, the data trends differently than expected, showing graphed curves (Figs. 6 & 7) rather than the expected relatively straight, positively-sloped line below the x-axis.
A mass gain in any sample group was difficult to understand within the test parameters. Both major procedures in this study, desiccation and extraction, remove content from tape, either water or degraded binder. Accordingly, both procedures were expected to cause a mass loss. Even if the acetone extraction test were to malfunction in terms of its specificity, and to remove other components in addition to the binder, a mean mass loss would still be the result. In order to cause a mass gain, something had to be added to the tape samples. One possible explanation is that the acetone was not completely driven off from the samples during the drying period after extraction.
Why would acetone remain in the samples? IPI post-ex traction recommendations call for 15 minutes of air drying, 15 minutes of oven drying, and another hour of reconditioning to the lab environment. This study's goal of examining desiccation without heat precluded drying in an oven. Instead, this study's samples were air-dried on filter paper for 30 minutes. Previous literature indicated that 30 minutes was sufficient time to drive acetone from a tape sample and allow the sample to equilibrate to its environment (Bertram & Cuddihy, 1982).
It is thought that acetone may have remained in the samples due to capillary action between the rolled layers of sample tape. Recall that the IPI study recommended accordion-folding samples instead of rolling. Accordion-folding might have solved the problem of acetone retained by capillary action. However, as discovered early in this study's methodology, accordion-folding is not a viable sample preparation method for shedding tape, such as the Shamrock 041. Future application of the acetone extraction method will require a sample preparation method that allows for effective drying without damaging the sample.
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
If acetone did remain on the samples after drying, then that acetone likely contained some of the degraded binder it extracted from the tape. A higher concentration of extracted, non-volatile binder would reduce the overall volatility of the acetone, making the tape slower to dry (E. Bradshaw, personal communication, 24 March 2010). The control group, which contained the untreated samples, would have yielded post-extraction acetone heavily laden with degraded binder, meaning that a relatively larger amount of remaining acetone would not easily evaporate. Other, desiccated test groups may have Welded remaining, post-extraction acetone less heavily laden with binder, meaning that relatively larger amounts of acetone would evaporate. This would mean that samples treated for less time or not treated at all would have the largest mean percent mass gain, as shown in this study.
Overall, though the significant differences found between test groups indicate that the desiccation treatment did produce an effect, the unexpected mean mass percent changes graphed in Figures 6 & 7 show that the effect did not occur in the expected way. Available time and resources preclude further exploration into the reasons that the trends revealed in these results do not match the expectations of the study. Proprietary variations in formulation make audio tape's aging behavior notoriously difficult to predict. It is hoped that the raw data produced in this study can aid in future studies of the subject.
One further note is relevant about the quality and stability of the two tape types. Upon visual inspection and gentle handling, the Ampex 456 tape appeared to be relatively stable. Very little media became detached from the substrate. The samples remained relatively dimensionally stable during acetone extraction, showing only a slight degree of stiffening and curling. Photomicrographs of the different samples all looked very similar. By contrast, the Shamrock 041 tape shed media readily. It was highly dimensionally unstable during extraction, displaying a high degree of stiffening and curling. Photomicrographs of the different samples look significantly different, both from one another, and before and after treatment.
These observed trends are mirrored in the data. The Ampex 456 tape displayed relatively small standard deviations in the collected test group data, as well as relatively small mean percent mass changes when the test groups were compared to the control group. The Shamrock 041 tape was much less predictable; it displayed comparatively large standard deviations in the test group data, as well as comparatively large mean percent mass changes when the test groups were compared to the control group. Overall, the combined observations and data paint a very general picture about the condition of these tapes; the Ampex appears to he a comparatively higher-quality, more stable tape, while the Shamrock appears to be a comparatively lower-quality, unstable tape. These characterizations correlate well with anecdotal knowledge about these tapes' behavior.
[FIGURE 8 OMITTED]
[FIGURE 9 OMITTED]
[FIGURE 10 OMITTED]
The results of this study show that desiccation for up to eight hours does not predictably impact the symptoms of sticky shed syndrome as measured in the mass change of acetone-extracted tape samples. Further developments in sample preparation methods for the acetone extraction test are needed in order to minimize potential sample damage and maximize drying ability.
It is not known whether the unpredictable results seen in two, four, and eight hours of desiccation would persist at longer test intervals. Just as required baking times appear to be lengthening (Hess, 2008), desiccation times may be affected by similar trends. Or perhaps desiccation alone is not enough to reduce sticky shed symptoms; perhaps heat, too, is a required element. If so. audio technicians must weigh short-term tape stability against possible long-term effects of exposure to heat. Such long term effects of heat exposure might provide a useful focus for future research.
Until more generalizable information on tape's aging behaviors is available, audio collections managers should continue to focus time and resources on digital preservation efforts to ensure the continuing availability of audio content. As seen in this study, the physical degradation of magnetic audio tape continues to be difficult to predict and remedy.
Many thanks to Richard Hess and Dr. Richard Bradshaw for revisions guidance; to Richard Hess and David Lennick for tape donations; to Karen Pavelka, Dr. Gary Geisler, and Dr. Lee Norris for technical assistance; and to Joshua Russell for laboratory support.
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Sources of Materials
Microscope, camera, lens, light, balance, glassware, acetone, filter paper, and gloves:
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Rhapid Gel, Mylar
330 Morgan Ave.
Brooklyn, NY 11211
Sarah Norris is a conservator at the Texas State Library and Archives Commission. She received her MS1S and CAS from the University of Texas Kilgarlin Center, and has held conservation technician positions at the Newberry Library, Harry Ransom Center, and Benson Latin American Collection. Sarah serves on the board of the Electronic Media Group of the American Institute for Conservation. She is a lifelong musician who performs and composes in Austin, TX.…
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Publication information: Article title: Effects of Desiccation on Degraded Binder Extraction in Magnetic Audio Tape. Contributors: Norris, Sarah - Author. Journal title: ARSC Journal. Volume: 41. Issue: 2 Publication date: Fall 2010. Page number: 183+. © Not available. COPYRIGHT 2010 Gale Group.
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