Analysis and Provenience of Minoan and Mycenaean Amber, II. Tiryns Beck, Curt W;Southard, Gretchen C;Adams, Audrey B Greek, Roman and Byzantine Studies; Spring 1968; 9, 1; ProQuest pg. 5 Analysis and Provenience of Minoan and Mycenaean Amber, II. Tiryns Curt W. Beck, Gretchen C. Southard, Audrey B. Adams THE GRAVE ROBBERS' HOARD known as the Tiryns Treasure in­ cludes two well-preserved and two (?) fragmentary gold-and­ amber objects which have been fully described but as yet not satisfactorily explained. The hoard was found in December, 1915, in the area of the Mycenaean lower town southeast of the citadel of Tiryns. Karol first thought that it had been buried in Geometric times but later2 changed his view in favor of burial "before the fall of the Mycenaean culture (vor dem Untergang der mykenischen Kultur)." It is now generally accepted that the objects in the hoard range widely within the Late Helladic period.s We are here concerned only with the gold-and-amber objects. Kar04 described them as "a pair of curious, wheel-shaped ornaments of goldwire, the spokes of which are set with amber beads." He added that the hoard yielded sufficient additional gold wire and amber beads to account for a second pair, and suggested that they may have served as "Schlafenschmuck" like the wheels covering the ears of the lady of Elche.5 In his first note, Karo6 supplied a photograph giving an axial view of one "wheel" containing seven amber beads (now Athens National Museum no. 6217b) and a side view of the other (now Athens National Museum no. 6217a) in which the amber cannot be seen clearly. In a somewhat later note, Philadelpheus7 described these objects as "three crowns (SuxS1}fLct'Tct) of woven gold wire ... containing crossed bronze rods in which large, rounded amber pieces are mounted"; he gave the number as three: two virtually intact and one of which only 1 G. Karo, AA 1916, 143-147. 2 G. Karo, AthMitt 55 (1930) 119-140. 3 H. W. Catling, ProcPS 22 (1956) 111. « Karo, supra n.l. 5 P. Paris, MonPiot 4 (1897) plate 13/14. 6 Karo, supra n.l. 7 A. Philadelpheus, De/tion 2 (1917) Suppl., 17. 5 6 ANALYSIS AND PROVENIENCE OF AMBER, II the amber pieces were found, although he listed two balls of gold wire (now Athens National Museum no. 6218). His illustrations show no. 6217a (with five amber beads) and no. 6217b (with seven amber beads); the third "crown" is represented by seven amber beads mounted on two modem metal rods, but without any gold wire. This is now Athens National Museum no. 6219. In his full publication of the Tiryns Treasure, Karos included photographs of the intact "crowns" in side views (Beilage xxx A, re­ produced as our PLATE 1) and in axial views (Beilage XXXI). He gave No. 6217A No. 6217B Figure 1. THE Two INTACT GOLD-AND-AMBER ORNAMENTS OF THE TIRYNS HOARD measurements of the amber beads but no designations for them. We have numbered the beads with Roman numerals (in the order in which Karo listed them) as shown in Figure 1 and in Table 1.9 Karo also illustrated the loose amber pieces mounted on their modern rods (Beilage XXXII); Figure 2 has been traced from his photograph. It shows, as did Philadelpheus' illustration,Io seven pieces of amber: four mounted on one rod and three on the other. Again we have numbered these with Roman numerals in Figure 2 and in Table 1 in the order in which Karo listed them. 8 Karo, supra n.2. I Karo's and our measurements do not agree exactly in all cases (cf. Table 1), but they agree closely enough for identification. We will not claim that our measurements are more accurate than Karo's, although they were taken with slide calipers; many of the amber beads, closely mounted on their bronze rods, are not easily accessible. There may also have been a reduction of size by breakage, or an increase by the application of protective coatings. 10 Philadelpheus, supra n.7. c. W. BECK, G. C. SOUTHARD, A. B. ADAMS 7 TABLE 1. DIMENSIONS AND SPECTROSCOPIC CLASSIFICATION OF AMBER BEADS IN TmYNs HOARD Athens Maximum Dimensions (mm) National Desig- Karo Authors Spectrum Extraneous Computer Museum nation L D L D Number Absorption Classifica- Number tion 6217 a-I 26 23 28 20.5 782 7.81-' Baltic a-II 25 18 28 20 785 7.8 P. (weak) Baltic a-m 24 15 25.5 15 a-IV 19 14 18.5 15 809 none Baltic a-v 39 22 42 15 786 7.8 P. Baltic and 790 b-I 26 33 25 33 b-II 19 29 19.5 22.5 783 7.8 p. Baltic b-m 24 24 25 23.5 b-IV 24 20 24.5 19.5 784 7.8 P. Baltic 791 7.25 and 7.8 p. Baltic b-v 12 26 14 28.5 b-VI 27 17 29 16 808 none Baltic b-VII 11 9 11.5 10 781 7.25 and 7.8 p. Baltic 6219 I 31 34 31 34 787 7.81-' Baltic 803 none Baltic II 27 36 29 36.5 799 7.25 and 7.8 p. Baltic 804 none Baltic m 20 37 19.5 36.5 806 7.25 and 7.81-' Baltic IV 20 31 18 32 807 7.8 P. (weak) Baltic v 17 15 22 15 VI 21 11 22.5 11 788 7.8 P. (weak) Baltic VII 13 20 no longer in collection not listed 13.5 11.5 unnumbered fragment 805 none Baltic unnumbered fragment 801 7.25 and 7.81-' Baltic unnumbered fragment 800 none Baltic However, we find only six amber beads mounted on the two modem rods in the National Museum, three on each. The seventh bead listed by Karo with a length of 13 mm and a diameter of 20 mm no longer exists. There is an unmounted bead, length 13.5 mm, dia- meter 11.5 mm, which cannot be Karo's No. 6219-vn and which is so badly weathered that it has been impossible to take a usable sample. 8 ANALYSIS AND PROVENIENCE OF AMBER, II In addition, there were eight fragments which may well be what remains of Karo's No. 6219-vn and of which we have sampled three as shown in Table 1. No. 6219 Figure 2. AMBER BEADS FROM THE TIRYNS HOARD MOUNTED ON MODERN RODS Sample Contanlination We have taken samples of thirteen of the eighteen whole mounted beads and of three of the fragments, for a total of sixteen samples. The sampling, never an easy matter with archaeological amber arti­ facts, was very much complicated by thick coatings of foreign mater­ ials. Doubtless because of their uniqueness, the amber of the Tiryns wheels has received rather more conservation treatment than has been good for it for analytical purposes. One heavy coating, which completely fills many of the cracks and drill holes of some pieces, has a waxy consistency. A sample of it gave the unmistakable infrared spectrum of beeswax.ll Inquiries at the National Museum yielded no information on this or other treatments; they were evidently made before records of conservation work were kept. A second treatment with a synthetic resin seems to have been made; again there is no record, and the resin now used at the National Museum, a com­ mercial fingernail polish, is not the same as that contaminating the Tiryns amber, as the infrared spectra clearly show. As had to be expected, these treatments produced extraneous bands in the infrared spectra of the amber. One of these, a band at about 11 W. Kuhn, Studies in Conservation 5 (1960) 74. " C. VV. BECK, G. C. SOUTHARD,A. B. ADAMS 9 7.8fL (1280 em -1), due to beeswax, is perilously close to the 8 to 9fL (1250 to 1110 em -1) region which we have found to be most useful for the identification of Baltic amber.12 Where enough sample was avail­ able for duplicate tests (samples 6217b-IV, 6219-1, and 6219-n), the inner surface of the sample chip which ought to be free (or freer) of contamination gave the better spectrum; indeed, in the two latter cases, it gave a perfect one. The second impurity is less prevalent. Five of the nineteen spectra run show a curious sharpening of the A B C D Figure 3. EFFECT OF IMPURfTIES ON THE 7.25 fL (1380 em-I) METHYL BAND OF AMBER A. Methyl band of amber. B. Methyl band of hypothetical synthetic resin. c. Super­ position of A and B. D. Methyl absorption band of contaminated Tiryns amber symmetrical methyl absorption at 7.25 fL (1380 em -1) as shown in Figure 3d. We have found a similar absorption pattern in the spectra of the surface, but not of the interior, of a Near Eastern amber object and we believe that the following considerations offer an explanation for it. Although the complete chemical composition of amber (and of all other fossil resins) is not yet known, all these resins give infrared spectra which leave no doubt that they contain several methyl groups in different molecular environments. Because of these slight differ­ ences in environment, the methyl groups absorb infrared radiation 11 C. W. Beck, GRBS 7 (1966) 191-211 and earlier work cited there. 10 ANALYSIS AND PROVENIENCE OF AMBER, II over a range of wavelengths near 7.25 p. (1380 cm -1) leading to a typically broad and rounded absorption peak as shown for Baltic amber in Figure 3a. Pure compounds, on the other hand, if they con­ tain only one methyl group per molecule, or if they contain more than one methyl group but in essentially identical environments, show very sharp absorption bands in this region, as in Figure 3b. This is precisely what would be expected from the theory of infrared spectroscopy, since only identically bonded methyl groups will require identical amounts of energy to support the vibrations which cause absorption of infrared light. Now if a sample contained a fossil resin with a broad methyl absorption band and, at the same time, a pure compound with a sharp absorption peak at the same wavelength, but of greater relative intensity, the absorption pattern would be a super­ position of Figures 3a and 3b as shown in Figure 3c. This is precisely the shape of the 7.25 p. (1380 cm -1) absorption in five of the spectra of the Tiryns amber samples, and we conclude that these samples have been treated with a compound containing a large number of identical methyl groups. This criterion is met by synthetic resins. While it is not possible to identify the contaminant from the sparse spectral evi­ dence, a synthetic lacquer of the vinyl acetate type is a very reasonable possibility.13 We have tried to remove these impurities with organic solvents in order to gain a H clean" amber sample which would give an infrared spectrum free of all extraneous bands. Amber itself is not completely soluble in any known material.14 To our disappointment, the contaminants proved to be exceedingly tenacious. Extraction with carbon tetrachloride, petroleum ether and ethyl acetate, in the cold or after boiling for as long as 30 minutes, failed to remove them, although it did reduce the intensity of the absorption bands which we ascribe to them. This in itself is good evidence that these bands are not caused by the amber, and we have therefore interpreted the spectra by ignoring them. As shown in Table 1, eight spectra have the band at 7.8p. (1280cm-1) which we assign to beeswax; five have both the sharp band at 7.25 p. (1380 cm -1), probably due to a synthetic varnish and the 7.8p. (1380 em-I) band of beeswax; only six spectra are en­ tirely free from extraneous bands. Because of the problems arising from such impurities we would 13 Chicago Society for Paint Technology, "Infrared Spectroscopy" (Chicago 1961) Spec­ trum no. 23. 14 L. Schmid, "Bernstein," in C. Doelter and H. Leitmeier, Handbuch der Mineralchemie IV.3 (Dresden and Leipzig 1931) 892. c. W. BECK, G. C. SOUTHARD, A. B. ADAMS 11 like to exhort archaeologists to avoid treating amber artifacts in any manner unless a piece cannot be taken from the site without consoli­ dation. In the very few instances where that is the case, we would recommend purified paraffin wax in preference to beeswax. Paraffin is quite as difficult to remove15 as beeswax, but it has fewer absorp­ tion bands in the infrared because it contains only carbon-carbon and carbon-hydrogen bonds, and these do not absorb infrared radiation in the range of 8 to 9 J.L (1250 to 1110 em -1) which we have found most useful for the identification of fossil resins. Synthetic varnishes should be avoided because they are notoriously difficult to remove and be­ cause they give complex infrared spectra. Provenience of the Tiryns Amber The infrared spectra of the 16 samples listed in Table 1 are shown in Figure 4 over the range of 8 to 9 J.L (1250 to 1110 em -1). Where two spectra were made of a given sample, the better one is shown. The slope of the absorption in this range is the most useful criterion for the recognition of Baltic amber. In a well-preserved specimen it has a value of zero between 8.0 and 8.5 J.L (1250 and 1175 em -1), i.e. there is a horizontal line or