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24 Assessing the Effects of Pesticidal Chemicals

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on Historic Textiles S. M. SPIVAK and J. WORTH

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Department of Textiles and Consumer Economics, University of Maryland, College Park, MD 20742 F. E. WOOD Department of Entomology, University of Maryland, College Park, MD 20742

In protecting textiles from insects, concern arises for the damage that the pesticidal chemical itself may cause to the textile object. A preliminary study was undertaken to assess this. Cotton and wool were each dyed with four natural dyestuffs. The dyed fabrics were exposed to pesticide-related chemicals for varying periods. Chemicals used were CCl (fumigant), dichlorvos (pest strip), petroleum distillate spray (carrier), and boric acid dusting. Instrumental colorimetry was used. There was no color change from CCl except for safflower-dyed wool after three years. Dichlorvos-treated samples varied, with some exhibiting a slight change. Petroleumd i s t i l l a t ewas hardly visible; most residue dissipated with no color change. Boric acid deposits were visible, but lessened after three years. Exceptions were strong color change on some wool samples. Breaking strength also was determined. Contact of the cotton by CCl resulted in degradation. 4

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TV/fan has associated himself with textiles in many forms for thousands -L*-"- of years. Articles of historic and artistic value commonly have been preserved in museums and homes, but not without complications. One of these complications in particular is the attack of insects. Fibrous and Current address: U . S. Small Business Administration, 1240 Cleveland, OH 44199. 1

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East 9th Street,

0065-2393/81/0193-0333$05.00/0 1981 American Chemical Society

Williams; Preservation of Paper and Textiles of Historic and Artistic Value II Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

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fabric materials can be attacked by a variety of insects, for example, the carpet beetle, clothes moth, silverfish, firebrat, and cockroach. Not all insects found in museum storage areas are necessarily damaging to textile materials, for instance, most flying moths are harmless to textiles. Alternately, insects such as termites inadvertently may damage textiles while normally feeding on other materials. Therefore, it is important for museum staff to have some familiarity with these types of insect species. In addition, pest control may be likened to the practice of medicine in that the prevention is easier than the cure. Efforts should be taken to avoid infestation of historic textiles rather than have to deal with an infestation after it has developed. An understanding of insect behavior is vital to instituting effective housekeeping and other preventative measures. If an infestation occurs, procedures must be selected that control the insect problem without damaging the textile. Protection of the historic textile is the ultimate goal. Therefore, one must select control procedures that are proved safe and effective, or know how to find knowledgeable experts who can recommend the most appropriate control procedures. One objective of this study is to highlight, for conservators and other museum professionals, an increasing need for attention to textile pests and their control. Rapidly changing local, state, and federal regulations, listing approved pesticides and their usage, make it imperative that museum personnel be cognizant of these dynamic changes and recent developments. This is especially important since the trend in regulation has been to restrict severely or control use of many of our proved and most effective pesticides. As a result of tightened restrictions and reduced use of pesticides, infestations are becoming more common and must be of concern to those with museum or historic textile collections. In addition, both new, exotic and older, forgotten measures of pest control have entered the available arsenal of pesticidal chemicals, and many of these are untried or unproved for safe use on historic textiles. The major objective of this chapter is to report on preliminary laboratory investigations that simulated pesticide treatments on historic type textiles and assessed the relative safety or potential damage commensurate with their use. This experimentation will demonstrate laboratory methodology and report on color or strength changes that may ensue with pesticide treatment. It also is hoped that others will recognize the need for further related work and expanded research efforts in this fruitful and neglected area will result. It is not the intent of this chapter to review the extensive information available on textile pests, specific insect identification, life cycle and habits, or detailed methods of control. However, reference will be made below to major works on textile pests and their control for use by the reader. Williams; Preservation of Paper and Textiles of Historic and Artistic Value II Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

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Pest Control of Museum Textiles There is an extensive literature on insects and insect control, although little is addressed directly to museums and conservation of historic objects, specifically textiles. A detailed review of "Textile Pests and their Control," including fungicidal and microbial problems, is that by Hueck (J) with extensive references contained therein. The subject also receives general treatment in Plenderlith and Werner (2). Identification and control of insect pests in general, including textile insects, can be found by SzentIvany and Beecher in the UNESCO conservation work (3,4). Fumigation of textiles is discussed by Rice (5) and a treatise on mothproofing textiles is by Moncrieff (6), the International Wool Secretariat (7), or McPhee (8). References in general entomology usually include insects specific to fabrics and paper, although the special concerns of museum or historic conservation, older materials and natural dyestuffs, usually are not considered. A comprehensive analysis of the complete insect-related problem, including fumigation and control of textile pests, is available in Ebeling (9), or in an earlier treatise by Mallis (10). Experimental Materials. In protecting textiles from the possibility of insect attack, a major concern arises for the potential damage that insecticidal chemicals may cause to the textiles. Two areas of damage that are of concern are color change and strength loss. Several chemicals that might be chosen for use in museums were tested to determine the extent of change in both color and strength from exposure to these chemicals. The chemicals chosen for experimentation were petroleum distillate, carbon tetrachloride (CC1 ), dichlorvos, and boric acid. Petroleum distillate is a light, refined oil that is a major component and carrier in many liquid or aerosol pesticide formulations. CC1 was tested because it represents a fumigant that can be used by museum staff in small, controlled exposures. D i chlorvos is becoming increasingly popular to museum staff and was used in the form of No-Pest Strip, in which the insecticide vaporizes at a controlled rate out of the solid strip. The active ingredient in these pest strips is 2,2-dichlorovinyl dimethyl phosphate, also known as D D V P or Vapona insecticide. Boric acid in dust form was selected because of its ready availability to the public, ease of application, and renewed interest in its long known effectiveness against roaches and beetles. Chemicals such as naphthalene and paradichlorobenzene, PDB, were not tested because of their prior widespread use by textile conservators, although long term effects are still questioned by some. Most textiles found in historic museums are natural fibers dyed with natural dyestuffs. Therefore, in this experiment two common textiles, cotton and wool, were dyed with safflower, madder root, logwood chips, and indigo. These dyes were chosen to represent a range of colors often found in historic textiles. The cotton and wool textiles were obtained 4

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from Testfabrics (11), which permits some control over the source and prior condition of the textile fabrics used in the investigation. The fabrics were dyed by the authors for uniformity of treatment and because naturally dyed cloth was not otherwise available. The processes used in this dyeing were those suggested by Kramer in Natural Dyestuffs (12). Alum was used as a mordant in all dyes except indigo where cream of tartar was used; other mordants might yield different results. Two tests were conducted to determine the influence of the pesticidal chemicals on the fabric. On the dyed fabric samples, color change due to chemical exposure was recorded both visually and with an instrumental colorimeter. On undyed cotton and wool fabrics, change in strength was determined using a tensile tester. Sample Preparation. CC1 was applied as a fumigant to fabric samples suspended near the bottom of a stainless steel dessicator. The CC1 liquid was placed in an open petri dish on a rack above the samples, since its vapor is heavier than air. Sufficient chemical was provided to maintain vapor equilibrium within the small, closed dessicator. Two days later, the CC1 was exhausted from the dessicator and it was resealed with the fabrics stored inside for four weeks, until the samples were required for testing. The fabric samples for exposure to dichlorvos were placed in a wooden, glass-topped museum case along with one No-Pest Strip in such a manner that the strip would not touch the samples. The time of duration to the dichlorvos vapor was four weeks, after which the fabric samples were removed from the museum case for testing. Petroleum distillate was applied to other fabric samples using a home or garden-type spray device, letting a light mist fall on the samples. Fabric samples were lightly covered with boric acid dust using a shaker device with small openings and brushing off the excess. The petroleum distillate and boric acid treated samples were then placed in separate but similar cases to the dichlorvos samples. These closed storage cases were of the type used in insect collections, and were kept covered with a dark cloth to avoid any fading from room light. After four weeks duration, the latter samples were removed from their storage cases for testing. All samples were returned to their respective cases and stored in the dark until removal for color and strength measurement after eight weeks duration. Thereafter, samples were kept in special envelopes until 160 weeks duration and again removed for color measurement. Measurement of Color Change. There were five replicates, each 3 in. X 3 in., of the individual treatments and control samples. These included both fabrics and the treatments comprising the four dyestuffs and four pesticide applications. The color of the dyed samples was evaluated using a Hunter Model D25M Laboratory Colorimeter. This color measurement device employs the L , a, b tristimulus value color order system. Each color is defined uniquely by its L, a, and b values. The L value represents whiteness-blackness; the a value represents red­ ness-greenness; and the b value represents blueness-yellowness. To evaluate the effect of each pesticide on the dyed fabrics, it is necessary to calculate the color change (Δ) from the specific L , a, and b values. The components of color change are determined by AL, change in white4

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ness-blackness; Δα, change in redness-greenness; and Ab, change in blueness-yellowness. From the individual components of color change, one obtains the total color difference, AE, in Judd-Hunter (13) terms given by: Δ# = (ΔΖ, + Δα + Δί) )

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Although the individual components can tell one how a color change differs from its control, it is the total color differences, AE, that is most often reported and will be the focus of the following results. There remains some question of interpretation regarding instrumentally measured color change values and how these compare with subjective perception of color change. As a recognized guide in evalua­ tion of the data reported below, AE values by this method would have to be significantly greater than 1.0 unit to be visually perceived by most observers as an actual color change. In this regard, however, a visual, subjective assessment of the color change also was obtained after 160 weeks, based on the opinion of several independent observers. This is reported by use of simple, descriptive adjectives that differ from terms otherwise used in industrial color matching. The reader is directed to Hunter (13) and Billmeyer and Saltzman (14) for further discussion of the principles of color order systems, tristimulus colorimetry, and its interpretation. Measurement of Strength Loss. The same test fabrics of 100% cotton and 100% wool were employed, although in this case undyed, to determine any potential loss in strength of the fabrics upon exposure to the four pesticides employed. Samples for the strength loss tests were prepared according to ASTM Standard Test Method D-1682-64, (15) raveled strip. Strips of the undyed fabrics were cut in the warp direction, lia in. χ 6 in., and ravelled to 1 in. X 6 in. Ten undyed samples of cotton and wool were treated in the same manner in chemical exposure as the dyed samples used in color measurement. After four weeks, these test samples were removed from their cases and their strength measured under ambient conditions using an Instron Model 1130 Tensile Tester. The change in strength due to exposure to the chemicals was determined by comparing the mean of each set of ten exposed samples with that of an unexposed control group and the findings reported. Results and Discussion Color Change. Tables I through IV summarize the color change data, obtained by comparison with an untreated/unexposed control sample, for the dyed cotton and wool fabrics exposed to CC1 , dichlorvos, petroleum distillate, and boric acid respectively. Each table reports the total color difference at 4, 8, and 160 weeks duration after initial treat­ ment. Also reported is a visual description of the perceived color change from the untreated control after 160 weeks. From Table I, CC1 samples, the cotton fabrics showed AE values about 1.0 or below, except for the logwood samples, which were slightly above 1.0. These changes were not readily apparent under visual inspec4

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Total Color

Cotton Fabric: Duration (Weeks)

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Dye Type Safflower Madder root Logwood Indigo

0.0 0.5 1.5 0.5

8

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0.8 0.7 1.3 1.2

0.5 1.1 1.2 0.7

none none none none

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Total Color Difference

Cotton Fabric: Duration (Weeks) Dye Type

4

8

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Visual

Safflower Madder root Logwood Indigo

0.7 1.0 1.8 0.4

1.1 1.3 4.2 1.4

0.8 0.6 2.0 0.4

none none trace none

Table III.

Total Color Difference

Cotton Fabric: Duration (Weeks) Dye Type

4

8

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Visual

Safflower Madder root Logwood Indigo

2.7 2.7 3.0 2.3

1.7 1.3 1.3 3.3

0.2 0.9 2.5 1.3

none none slight none

Table IV. Total Color Difference Cotton Fabric: Duration (Weeks) Dye Type

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Safflower Madder root Logwood Indigo

6.2 6.2 4.6 6.8

6.7 7.0 6.3 6.4

1.6 1.1 1.7 0.3

none none slight none

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Difference ( Δ Ε ) — C C l Samples 4

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Wool Fabric: Duration (Weeks) 4

8

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Visual

0.6 0.6 0.6 1.1

0.7 0.9 0.1 1.4

3.2 1.0 1.3 0.8

noticeable none none none

(ΔΕ)—Dichlorvos Samples Wool Fabric: Duration (Weeks) 4

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Visual

0.6 0.4 0.4 0.6

0.6 0.9 0.9 1.1

1.6 2.4 1.3 1.6

none slight none none

(ΔΕ)—Petroleum Distillate Samples Wool Fabric: Duration (Weeks) 4

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Visual

2.5 3.0 3.0 2.1

2.4 2.2 2.3 1.3

1.7 1.9 0.7 0.7

none none none none

(ΔΕ)—Boric Acid Samples Wool Fabric: Duration (Weeks) 4

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3.5 4.6 2.9 5.4

2.6 7.3 3.0 6.2

3.0 2.5 4.3 0.7

noticeable slight severe none

Williams; Preservation of Paper and Textiles of Historic and Artistic Value II Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

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tion. The woolen samples behaved similarly to the cotton over all time periods with one notable exception, the safflower at 160 weeks. In this case, a noticeable color change developed sometime between 8 and 160 weeks and this was equally recorded by the colorimeter as a sizeable AÉ of 3.2. The dichlorvos treated samples, Table II, show varying AE values, representing in most cases no significant color change. However, data for the logwood dyed cotton sample indicate color change at both 8 weeks and reconfirmed at 160 weeks. The madder root dyed wool exhibited some or slight color change at 160 weeks (ΔΕ of 2.4) although not at the earlier times. The data for wool suggests that the color difference values may be increasing with time, although this is not the case with the cotton fabric. Table III summarizes total color difference for the samples sprayed with petroleum distillate. The general trend for both cotton and wool fabrics with all dyestuffs is for a lessening in the apparent color change over time. At four weeks, all ΔΕ values are between 2.1 and 3.0 and the samples exhibited a noticeable darkening from the presence of the distil­ late oil. At 8 weeks, there is a tendency toward lower ΔΕ values, which continues thereafter. At 160 weeks, ΔΕ values are all below 2.0, with the exception of logwood dyed cotton, which still showed a slight color change. These findings can be explained by the nature of petroleum distillate, which is a lightweight, refined oil. After application, some of the lower molecular weight fractions may evaporate slowly while other portions of the oil will dissipate into any contiguous materials in contact with the fabrics, such as paper liners in the museum cases or paper storage envelopes. The net effect is that eventually the petroleum distil­ late becomes too dilute to be seen by most observers. The boric acid dust on the samples (Table IV) was very noticeable as a light deposit, both upon application and at 4 or 8 weeks. In an effort to remove some of this residue, a laboratory vacuum was used on the samples at 8 weeks, and color change immediately following is reported in Table IV as 8 vac. These results are as severe as those reported earlier. But at 160 weeks, there is a sizeable reduction in AE values for all cotton samples and only logwood indicates a slight change remaining. The wool fabrics dyed with indigo and madder also showed lower AE values at 160 weeks, but a noticeable color change remained on most samples. The logwood dyed wool exhibited the most obvious and severe color change to boric acid (and at 160 weeks, the highest AE, 4.3), showing a pronounced reddish color from the otherwise brownish samples. The reduction in some of the above AE values for boric acid is believed to be a hygroscopic absorption of moisture by the boric acid powder, reducing the granular size and causing a more uniform but less noticeable deposit on the fabrics. Williams; Preservation of Paper and Textiles of Historic and Artistic Value II Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

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Table V. Breaking Strength of Fabrics Exposed to Chemicals Breaking Strength (kg) Treatment Control (untreated) Petroleum distillate Dichlorvos CCl Boric acid 4

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Cotton

β

17.5 ± 20.8 ± 21.2 ± 16.7 ± 20.1 ±

a

Wool

1.6 2.3 1.7 6.0 2.0

14.0 ± 1.2 14.7 ± 1.1 14.4 ± 1.1 14.2 db 1.5 15.7 ± 0.8

Data do not include accidental sp llage samples. ;

Strength Loss. The breaking strength of undyed cotton and wool fabrics exposed to each of the four pesticides, and measured after 4 weeks, are summarized in Table V. A comparison of each test value with the untreated control determines if any strength loss has occurred under our test conditions. It appears from these data that strength changes attributable to the chemical exposure were not significant at 4 weeks, that is, no strength loss occurred under these given set of conditions. The breaking strength of the test samples appears inexplicably higher in some cases than in their respective controls. However, the approximate ± range values (also shown) are sufficiently large to suggest that there are not real differences between the strength of the test samples and that of the controls. An additional set of strength samples was not available for test at 160 weeks, so that any latent or long term degradation could not be determined. Several cotton samples, when treated with C C I 4 , were contaminated inadvertently by direct spillage of the chemical. These specific samples developed stains over time and showed a marked drop in strength, with the sample breaking during the stress test at the point of staining. Those cotton samples that were not stained did not show this strength loss. It can be concluded that the presence of the CC1 directly on the cloth caused a strength loss, which is assumed to be through the formation of hydrochloric acid by hydrolysis. However, the same chemical used as a fumigant did not exhibit this behavior and only uncontaminated samples were reported in Table V. 4

Conclusions These experiments to determine color change and strength loss through use of pesticidal chemicals were intended to illustrate that such treatments and conditions may or may not be harmful to historic textiles. No overall generalizations can be made since the findings indicate that specific effects are attributable to fiber type, dyestuff, and pesticide treat­ ment. In most cases, no long term color changes resulted, but in selected Williams; Preservation of Paper and Textiles of Historic and Artistic Value II Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

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cases, very noticeable changes remained after three years. Certain color and strength problems discussed earlier with the use of boric acid and CC1 were attributable to direct contact of the chemical with the fabric. If care is taken that contact does not occur, their possible use may be condoned for control of infestation. Petroleum distillate used alone appears safe, as determined by color and strength measurements. How­ ever, in normal use it would be combined with small quantities of other ingredients, in which case the safety is further dependent upon the ingredients added. The test samples treated with dichlorvos showed little or no change of color or strength. These results do not give unequivocal answers to the safe use of pesticidal chemicals, especially on antiquated and/or degraded materials, or for very lengthy periods. However, the experimentation illustrates how such chemicals can be tested under carefully controlled conditions and any changes in color or strength numerically assessed. Combined with prior experience, surveys and ongoing testing of pesticides by museum conservators in the field, the laboratory evaluations provide an important guide for specific recom­ mendations of pesticide use with museum textiles. The authors recognize several limitations of this preliminary study, along with suggestions for further work. The current research has focused only on cotton and wool textiles. Other materials such as leather, feathers, or plastic may be not necessarily amenable to similar conclusions. The general scope of the research should be expanded to include the manmade or aniline type dyes that were used increasingly in the nineteenth and early twentieth century. Likewise, there are numerous pesticides and fumigants, presently in use or suggested for use by conservators, which should be included in such controlled exposure type testing. There are unresolved questions that could not be answered in this work, but would benefit from further study. For example, how much color change occurred in the dyed, control sample itself, independent of any pesticide exposure? Was there any dye-fabric interaction that would have resulted in a change of color with time? Is there a rigorous, uncomplicating means of accelerated aging the dyed fabrics prior to pesticide exposure? In this latter regard, most museum materials will have already "aged" fifty or one hundred years before they might be subjected to a serious pesticide regimen, e.g., for control of an infestation. Lastly, there are external factors of operator safety, plus local, state, and federal regulations, which must be considered by all researchers, con­ servators, or other users of pesticidal chemicals. The best cure for insect attack is effective prevention. Careful, periodic inspection, housekeeping, and judicious use of pesticides can be valuable in preventing the need for heroic but potentially dangerous measures to the collection should a full infestation develop and strong treatment be prescribed. Awareness of the insect problem, attention to 4

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preventive maintenance, and a working relationship with a knowledgeable expert in textile/museum pest control are vital.

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Literature Cited 1. Hueck, H. J. In "Textile Conservation"; Leene, J. E . , Ed.; Smithsonian Institution: Washington, DC, 1972; Chap. 6, pp. 76-97. 2. Plenderleith, H. J.; Werner, A. E . A. "The Conservation of Antiquities and Works of Art," 2nd ed.; Oxford University Press: London, 1971. 3. Szent-Ivany, J. J. H. In "The Conservation of Cultural Property"; "Identification and Control of Insect Pests," UNESCO: Paris, 1968; pp. 53-70. 4. Beecher, E. R. In "The Conservation of Cultural Property"; UNESCO: Paris, 1968; pp. 251-264. 5. Rice, J. W. Textile Museum Journal 1969, 2(4), 31-33. 6. Moncrieff, R. W. "Mothproofing"; Leonard Hill: London, 1952. 7. International Wool Secretariat, "The Mothproofing of Wool," International Wool Secretariat, London. 8. McPhee, J. R. "The Mothproofing of Wool"; Merrow, Watford, Herts.: England, 1971. 9. Ebeling, W. "Urban Entomology"; University of California: Los Angeles, 1975. 10. Mallis, A. "Handbook of Pest Control," 3rd ed.; Mac Nair-Dorland: New York, 1960. 11. Testfabrics, P.O. Box 118, Middlesex, NJ 08846. 12. Kramer, J. "Natural Dyes: Plants and Processes"; Scribners: New York, 1972. 13. Hunter, Richard S. "The Measurement of Appearance"; Wiley-Interscience: New York, 1975, pp. 13, 140, 151. 14. Billmeyer, F. W., Jr.; Saltzman, M. "Principles of Color Technology"; Wiley-Interscience: New York, 1966. 15. "Annual Book of ASTM Standards: Part 32—Textiles"; American Society for Testing and Materials: Philadelphia, 1974 (or annually). RECEIVED November 5, 1979.

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