Brill, Robert H. “Chemical Analyses of Amelung Glasses: III. Chemical Analyses and Other Laboratory Studies...” The Journal of Glass Studies vol. 18 (1976): 224-237. III. CHEMICAL ANALYSES AND OTHER LABORATORY STUDIES OF GLASS FRAGMENTS EXCAVATED AT THE SITE OF THE NEW BREMEN GLASSMANUFACTORY R.H.BRILL THE OBJECTIVE OF THIS STUDY was to deter- confident that the colorless specimens and cul- mine what chemical compositions or peculiari- let analyzed here really were made at this fac- ties might characterize the glass excavated at tory. Moreover, the indications are that the the site of John Frederick Amelung's New specimens of more ordinary glasses also were, Bremen Glassmanufactory.l From among the because, as will be demonstrated below, their thousands of fragments excavated, thirty were compositions closely match those of knock-offs selected for chemical analysis. The sampling and drippings. Only two specimens are really was not intended to be representative, in a pro- suspect of having outside origins. The dates of portional sense, of the entire body of glass un- the specimens analyzed are assumed to fall covered. Instead, there was a strong bias in the somewhere within the factory's operating pe- sampling towards colorless glasses, which evi- riod, that is, 1785 through 1795, although they dently were used for fine quality production. are associated with the building which is be- About half of the specimens analyzed (fourteen lieved to have burned in 1790 and not been fragments) are of this colorless glass. These rebuilt afterwards. were chosen in the hope of establishing com- Quantitative analyses by atomic absorption positional connections with museum objects at- were carried out for the follOWing elements, ex- tributed to Amelung. The remainder consists of pressed throughout as weight percentages of a small assortment of colored glasses (purples the oxides: 2 potassium (K20), calcium (CaO), and blues) and several specimens thought to sodium (Na20), magnesium (MgO), aluminum represent production of more ordinary wares (AbO:; ), iron (Fe20 3), and manganese (MnO). or window glass. A list of sample descriptions Phosphorus (P20 5) was determined colorimet- is appended at the end of this text. rically. All of the other elements at minor and The sampling contains specimens recogniz- able as vessel fragments, some cullet, and waste 2. For readers unfamiliar with chemical symbols, the formulas below represent the oxides of the corre- glass, such as drippings and knock-offs. One sponding chemical elements. can rarely be absolutely certain that particular SiO, silicon PbO lead glass vessel fragments or even pieces of cullet K20 potassium BaO barium CaO calcium SrO strontium must necessarily have been made at a factory Na,O sodium As,O, arsenic site because they were excavated there. Some MgO magnesium LbO lithium scrap glass and cullet could always have been Al,O, aluminum Rb,O rubidium Fe,0 3 iron B,0 3 boron brought into a factory. However, we feel quite Ti02 titanium V20 3 vanadium Sb,O, antimony NiO nickel 1. The factory will be referred to here simply as " the MnO manganese ZrO, zirconium Amelung factory" without intending to imply either CuO copper Bi,0 3 bismuth that it was the only "Amelung factory" or that it was CoO cobalt P,O. phosphorus always under the control of John Frederick Amelung. Sn02 tin 224 Rakow Research Library, The Corning Museum of Glass - http://www.cmog.org Brill, Robert H. “Chemical Analyses of Amelung Glasses: III. Chemical Analyses and Other Laboratory Studies...” The Journal of Glass Studies vol. 18 (1976): 224-237. trace levels were analyzed by semi-quantitative factory or if it is an intrusion or glass brought emission spectroscopy. Duplicate determina- in for cullet. It appears that the majority of tions starting with new samples were run for glass made at this factory, if not all of it, was any questionable values. Silica (Si02) was esti- of non-lead formulations. mated by difference from 100 percent. The second important observation is that al- Several special reference glasses were pre- though all the glasses are potash :lime formu- pared for these analyses and for the object lations (excluding the one lead glass), two analyses carried out at Winterthur. These distinctly different categories emerge from the included "synthetic Amelung glasses" which data. One is a low-lime formulation, and the contained major, minor, and trace elements at other a high-lime formulation. The low-lime levels corresponding to those obtained in pre- group has an average CaO content of 9.05 per- liminary studies. Analyses of the synthetic cent. It contains eighteen glasses ranging from Amelung glasses yielded excellent agreement 7 .08 to 10.8 percent CaO. The high-lime group with the theoretical compositions calculated has an average CaO content of 19.6 percent. It from the known batch compositions.3 There- contains five glasses ranging from 18.6 to 20.6 fore, the analytical procedures used are closely percent CaO. The separation between the calibrated for the analyses of both the Ame- groups is well-defined, and there is no over- lung fragments and the objects.4 lapping. The data are summarized in Table 1 and The data for the other chemical elements re- compiled in Tables 2-5. The specimens are enforce the separation. The same specimens grouped according to two main categories which cluster together in the low-lime group which emerged from the results and are ar- also cluster together in their percentages of ranged within those categories according to other chemical elements. Similarly, the speci- color. mens in the high-lime group remain clustered The first important observation made was in the other chemical elements. In all, ten dif- that all but one of the specimens are potash: ferent chemical elements serve to discriminate lime :silica glasses (K20 :CaO :Si02). Whereas between the two chemical types. The discrimi- lead (PbO) was frequently found at trace or nating oxides are: CaO, K20, Na20, MgO, low minor levels, a fact of some significance, it AbO ~ , Fe20~, SrO, BaO, PbO, and ShOG. was a major component in only one specimen, There are two partially-discriminating ele- no. 4283. This fragment, a stem base with fac- ments, P205 and Ti02, while MnO and B20 ~ eted cutting, is a true lead glass, containing are nondiscriminating. Repeat analyses will be 34.5 percent PbO. The question arises as to required to establish whether or not LbO and whether it was actually manufactured at the Rb~O are discriminating. The sharp separation into two groups proves 3 . The reference glasses used for all analyses re- to have a rational basis in that all the glasses in ported here are listed below. All the glasses were pre- the low-lime group are either colorless, purple, pared by Dr. August A. Erickson of Corning Glass Works and his co-workers. or blue. Clearly, this composition reflects the a) Nos. 611 , 612, 614, and 616 distributed by the basic formulation used for manufacturing the National Bureau of Standards. "fine glass" production of the factory. All of b) Reference glasses A, B, and D of a series pre- pared for The Corning Museum of Glass for the specimens in the high-lime group are green, interlaboratory comparison analyses. aqua, or amber-the colors characteristic of c) Three glasses prepared for The Corning Museum more ordinary production. The chemical groups of Glass, which contain only the major ingre- dients in the reference glasses A, B, and D and are tight and the separation is complete, there not the trace elements. being no crossovers between the two groups. d) Glasses SPE, TVX, and TVY prepared for The There are six glasses which have been desig- Corning Museum of Glass simulating the com- positions anticipated for the Amelung glasses. nated intermediate or uncertain as shown in Table 5. There are various ways of interpreting 4. The only discrepancy was in one glass, where the Y,0 3 by conventional x-ray fluorescence yielded a value their analyses. Two of them (nos. 346 and 573) of 0.06 percent instead of the theoretical 0.10 percent. could possibly be glasses made by melting to- 225 Rakow Research Library, The Corning Museum of Glass - http://www.cmog.org Brill, Robert H. “Chemical Analyses of Amelung Glasses: III. Chemical Analyses and Other Laboratory Studies...” The Journal of Glass Studies vol. 18 (1976): 224-237. gether a mixture of glasses of the low-lime and colored by tne addition of cobalt imported in high-lime groups. The others could be badly the form of zaffre or smalt. off-composition examples of the low-lime and The purple glasses (nos. 347, 348, 362, and high-lime groups. Alternatively, some of these 568) are all colored, as is to be expected, with six might be intrusions on the site-especially manganese (MnO) at a level of approximately the bottle fragments-or could be scrap glass 2-3 percent. The ingredient used to introduce brought in for remelting as batch cullet. Among the manganese also brought in barium (BaO), these, only no. 350, an irregularly-shaped piece lead (PbO), nickel (NiO), copper (CuO), vana- of waste glass, was certainly melted at the site. dium (V205), some aluminum (Ab03), and Its unusual color, probably the result of devitri- possibly bismuth (Bi203), zinc (ZnO), and tin fication, is consistent with its identification as (Sn02). an off-composition waste glass. The others ap- The presence of manganese in all of the frag- pear to be fragments of vessel or window glass. ments from the site, the low-lime, the high- It is probably wiser not to press too far in lime, and even the uncertain group, ties the interpreting these analyses now, but to await glasses together somewhat.