Chemical Investigations on Pre-Columbian Archaeological Textile

18 Chemical Investigations on Pre-Columbian Downloaded by UNIV ILLINOIS URBANA-CHAMPAIGN on November 21, 2016 | http://pubs.acs.org Publication Date: December 17, 1978 | doi: 10.1021/ba-1977-0164.ch018

Archaeological Textile Specimens N. S. BAER Conservation Center, Institute of Fine Arts, New York University, 1 East 78th St., New York, N.Y. 10021 M. DELACORTE The American Museum of Natural History, New York, N.Y. 10024 N. INDICTOR Chemistry Department, Brooklyn College, City University of New York, Brooklyn, N.Y. 11210

Nineteen archaeological pre-Columbian textile specimens from the collections of the American Museum of Natural History and the Metropolitan Museum of Art were examined. The textiles (Huari/Tiahuanaco, Ica, Paracas-Cavernas, and Paracas-Necropolis) are described. Elemental analyses for archaeological textile and modern wool samples (C, H, N, S, and ash) are reported. Elemental analyses for samples treated with distilled H O and CCl4 are compared with analyses of modern wool samples similarly treated. An unambiguous direct correlation between loss of sulfur and embrittlement could not be made. The possibilities of dating and provenance determination by technical means are discussed. 2

rchaeological excavations at pre-Columbian sites have yielded especially rich collections of textile artifacts. These materials often reveal information of considerable anthropological and art historical sig nificance. The difficulties of restoration, maintenance, and exhibition for archaeological textiles are well known to conservators and art historians ( 1 ). These materials are frequently recovered in a severe state of deterio ration ranging from dangerous embrittlement to extreme friability. The

1

261 Williams; Preservation of Paper and Textiles of Historic and Artistic Value Advances in Chemistry; American Chemical Society: Washington, DC, 1978.

262

PRESERVATION OF

Table I.

AND

TEXTILES

Locations of Archaeological Sites and Period Attributions of Specimens Examined

Culture or Site Huari/Tiahuanaco lea Paracas-Cavernas Downloaded by UNIV ILLINOIS URBANA-CHAMPAIGN on November 21, 2016 | http://pubs.acs.org Publication Date: December 17, 1978 | doi: 10.1021/ba-1977-0164.ch018

PAPER

Paracas-Necropolis

Period of Specimen 8 t h - l l t h century A.D. Somewhat before 2nd-3rd century B.C. 2nd-3rd century B . C

Description Bolivia Peru, south coast Peru Peru

many pathways to the deterioration of textiles make the condition of a textile an unreliable indicator of age. Deterioration can arise from ther mal, light, chemical, mechanical, or biological sources and may affect the proteinaceous substrate as well as the naturally associated oleagenous materials (2). Prolonged exposure to heat or light generally lowers the molecular weight, reduces sulfur content, and causes marked alteration in physical properties. Textiles are also constantly subject to hydrolytic and oxidative deterioration (3,4). Handling, storage, washing, cleaning, colorants, light, moisture, insects, fungi, and general environmental con ditions can all play a part in the breakdown of the artifact. Radiocarbon analysis is possible for dating ancient textiles only where sufficient sample is available. Unfortunately, the uncertainty in dating becomes unacceptably large with small sample size, contamina tion, and specimens of lesser antiquity (5). Chemical methods of dating are mainly limited to the observation that reducing the sulfur content of wool textiles appears to coincide, in some cases, with embrittlement and/or age (6). The presence of certain kinds of dyes and the manner in which they fade are sometimes used as the evidence of provenance (7). The moderate success achieved in describing some Ancient Near Eastern ivories by examining their elemental analyses and observing a characteristically diminishing proteinaceous content (8) has suggested the examination of archaeological wool textiles i n a similar manner. In the present study, elemental analyses and ash content are reported for 19 pre-Columbian textile specimens. The sites at which the textiles were excavated are given in Table I, and the individual specimens examined, including collection and accession number where available, are described in Table II. The results of the analyses for the archaeological specimens are compared with those of modern wool specimens. Experimental Specimen Selection. Specimens supplied by the American Museum of Natural History and the Metropolitan Museum of Art were chosen for well documented archaeological excavations. Most of the specimens

Williams; Preservation of Paper and Textiles of Historic and Artistic Value Advances in Chemistry; American Chemical Society: Washington, DC, 1978.

18.

BAER E T A L .

Table II.

Pre-Columbian Archaeological Textile Specimens 263

Descriptions and Designations of Textile Specimens

Downloaded by UNIV ILLINOIS URBANA-CHAMPAIGN on November 21, 2016 | http://pubs.acs.org Publication Date: December 17, 1978 | doi: 10.1021/ba-1977-0164.ch018

Specimen

Source

Description

T-1976-01

Vermont sheep wool. Sheared and hand spun in 1975 by Shelburne Spinners, Vermont. Supplied by M . Ballard (MB-1), Institute of Fine Arts.

T-1976-08

Mexican sheep wool. Spun 1973. Supplied by N. Kajitani, Metropolitan Museum of Art.

T-1975-01

Single twisted red-brown strand. Mummy bundle B. J. Tello find. Paracas.

AMNH°

T-1975-02

Single twisted black strand. Mummy bundle B.

AMNH

T-1975-03

Single twisted dark green strand. #41.0/1543. Paracas.

AMNH

T-1975-04

Single twisted red strand. Paracas.

AMNH

T-1975-05

Single twisted red strand. Mummy bundle B. Shirt Epaulet. J. Tello find (1929). Paracas Necropolis.

AMNH

T-1975-06

Single twisted red-brown strand. Mummy bundle B. J. Tello find. Paracas.

AMNH

T-1975-07

Single twisted ochre strand. #41.0/1543. Paracas.

AMNH

T-1975-08

Single twisted black strand. Mummy bundle B. Shirt Epaulet. J. Tello find. Paracas Necropolis.

AMNH

T-1975-09

Two twisted light yellow-ochre strands. Depart ment of lea. Myron I. Granger expedition, Roland L. Olsen, Collector (1930-1934). #41.0/5296-5699.

AMNH

T-1975-10

Two twisted ochre strands. Supplied by J. B. Bird (JB-1B). #41.2/954.

AMNH

T-1975-11

Single twisted ochre strand. Fringe from mantle. Paracas Necropolis, ca 300-200 B.C.

MM A

Single twisted red strand. Fringe from mantle. Paracas Necropolis, ca 300-200 B.C.

MMA

Padding from inside trophy head. Associated with pottery, gold, and textiles. Supplied by J. B. Bird (JB-8). #41.2/6039b. Paracas Cavernas.

AMNH

S-twisted strands of red, brown, and shades of gold. Interlocking tapestry weave. Supplied by J. B. Bird (JB-6). #41.0/5426. Tiahuanacan? Valley of Nasca.

AMNH

6

C

T-1975-12

C

T-1975-16

d

T-1975-17


264

PRESERVATION OF P A P E R A N D TEXTILES

Table II.


Specimen

Continued

Description

Source

T-1975-18

Strands (Z-twist) and cotton padding from false head from mummy. Supplied by J . B . B i r d (JB-7). #41.0/5525. Paracas.

AMNH

T-1975-19

Single S-twisted stand. Cloth from outside trophy head. Supplied by J . B . B i r d (JB-9). #41.2/6051/

AMNH

T-1975-20

Three light brown strands woven with black strands. Light brown appear to be S-twist warp, and black appear to be weft. Also black dyed border. Supplied by J . B . B i r d (JB-5). #41.0/5425. Tiahuanacan, Valley of Nasca.

AMNH

T-1975-21

Single S-twisted strand. Central seam area. Supplied by J . B . B i r d (JB-2). #41.2/780. Coast Tiahauanacan.

AMNH

T-1975-23

S-twisted white warp and slight Z-twisted gold weft. Cotton warp, wool weft. Supplied by J . B . B i r d (JB-1). #41.2/954. Tihuanacan.

AMNH

° A M N H denotes the American Museum of Natural History. * M M A denotes the Metropolitan Museum of Art. Single strands taken from the same mantle. Samples from same trophy head. 6

c

d

Figure 1.

Vermont sheep wool sheared and hand spun in 1975 by Shelburne Spinners, Vermont. Specimen No. T-1976-01.



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Figure 2. Cotton padding from inside trophy head. Paracas-Cavernas, Peru, ca. 2nd-3rd century B.C. Specimen No. T-1975-16. were colored wool though several of them were cotton or mixed warp and weft (see Table II). Figures 1-4 illustrate typical specimens. Analyses. Analyses of ash, carbon, and hydrogen by combustion; nitrogen by Dumas and micro-Kjeldahl methods; and sulfur by E D T A colorimetry were obtained from Schwarzkopf Microanalytical Labora tory, Woodside, N.Y. 11377. Analytical Errors. Errors associated with these data arise from uncertainties in the analytical methods and from impurities introduced into or present in the textile. These added materials include inorganic salts from groundwaters, dye materials, and organic materials introduced in the conservation laboratory to soften friable artifacts (9). The uncertainties for the analytical methods are as follows: ash by combustion residue, ± 0 . 3 % absolute; C, ± 0 . 0 5 mg C; H , ± 0 . 3 % abso lute; and N, by Dumas, ±ju,L or by micro-Kjeldahl, ±/xg (10). In general, sample sizes were: C, H , and ash, 4r-8mg; N, 5-9 mg; and S, 7-14 mg. The large uncertainties in the measurements of carbon and hydrogen limit the usefulness of data for these elements for very small samples. Methods for lubricating brittle textiles artifacts (9) lead to high carbon and high hydrogen values generally. The treatment history of the speci mens examined suggests that they were stored without further conser vation. Washing. Weighed samples of textile were immersed in 25-50 mL of distilled water or reagent grade CC1 in a stoppered iodine flask at ambient temperature without agitation. After 24 hr, the samples were removed from the wash liquid and dried to constant weight in a constant temperature humidity room (23°C; 50% r.h.). Dyed samples washed in 4



266

PRESERVATION OF P A P E R A N D T E X T I L E S

Figure 3.

Twisted red-brown wool strand from mummy bundle, Paracas, Peru, ca. 2nd-3rd century B.C. Specimen No. T-1975-01.

Figure 4. Three light brown strands woven with black strands. Huari/ Tiahuanaco, Valley of Nasca, Bolivia. 8thr-llth century A.D. Specimen No. T-1975-20. water lost approximately 10% of their original dry weight, and the wash water developed color. Identical samples washed i n CC1 lost negligible weight, and colors appeared to be fast. 4

Results Modern Wool. Table III gives the animal sources and Latin names of types of wool commonly encountered. Table I V presents literature values of the elemental analyses reported for wool together with several



18.

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analyses of modern samples from various sources. In general, the C analyses are just under 50%, N is « 1 4 - 1 6 % , S is 3-3.7%, and ash was 0-2.3% for modern samples, depending on source and processing. Archaeological Specimens. Table V presents data for the elemental analyses of untreated textile samples together with elemental analysis of modern samples for comparison. The archaeological samples all have lower C and H values than the modern samples. Nitrogen analysis is generally lower although one sample actually gave a significantly higher value than the modern samples. Sulfur content was about as frequently higher in archaeological samples as lower. An earlier study (Table VI) linked the embrittlement of ancient textiles with a depletion of sulfur and/or nitrogen (6). The extensive data of Table V clearly suggest the inadequacy of this generalization. The ash content of archaeological samples, though quite variable, is appreciable (2.4-9.4%) in all samples thus far examined. The sources of ash may be accretion from the burial or residue from the dying processes. Table III.

Animal Sources of Common Wool and Related Materials

Material

Source

Alpaca" Camel's hair Cashmere wool Llama Mohair Vicuna Wool (common)

Alpaca Bactrian camel Cashmere goat Llama Angora goat Llama vicuna Sheep

Latin Name Lama pacos pacos Camelus bactrianus Capra hircus laniger Lama glama glama Capra hircus aegagrus Lama vicugna genus Ovis

° Guanaco, vicuna, llama, and alpaca are four species of the camel family found in South America.

Table IV.

Analyses of Modern Wool Specimens

No.

C(%)

H(%)

N(%)

S(%)

0*

1 2 3 4 5 6 7 8

49.2 — — — — 49.97 46.05 —

6.6 — — — — 7.23 7.21 —

15.8 16.69 16.5 — 14.7 13.69 14.68 15.4

3.7 3.5 3.34 2.8-5.8 3.0 3.02 3.06 3.7

24.7 — — — — 26.09 26.7 —

b

C

d

Ash(%)

Ref.

0 2.3 —

11 2 12 13 6 this work this work 6

° Oxygen by difference in percentage from 100. * Sample T-1976-01. Sample T-1976-08. Alpaca wool. e

d


268

PRESERVATION O F P A P E R A N D TEXTILES

Table V . Analyses of Untreated Archaeological Textile Samples Sample


a

T-1976-01 T-1976-08 T-1975-01 T-1975-02 T-1975-03 T-1975-04 T-1975-05 T-1975-06 T-1975-07 T-1975-08 T-1975-09 T-1975-10 T-1975-11 T-1975-12 T-1975-16 T-1975-19 T-1975-17 T-1975-18 T-1975-20 T-1975-21 T-1975-23

C(%) 47.97 46.05 42.21 42.98 40.73 39.67 42.56 43.37 40.07 41.02 44.52 43.60 42.40 42.20 41.55 39.62 42.77 41.37 39.19 38.89 39.74

H(%) 7.23 7.21 6.36 6.20 5.92 6.05 6.17 6.75 5.90 5.70 6.32 6.35 6.03 6.52 6.57 6.79 6.66 6.20 6.14 5.91 6.40

N(%) 13.69 14.68 12.38 13.81 11.35 11.87 13.15 13.28 12.56 13.05 14.18 17.22 12:46 12.08 0.57 0.46 13.18 0.43 7.96 5.32 9.45

S(%) 3.02 3.06 3.78 3.99 3.14 3.41 3.48 3.79 3.41 3.80 4.08 3.91 2.94 3.46

Chemical Investigations on Pre-Columbian Archaeological Textile

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