Chemical Composition: ICP-MS/AAA data from sample, Leaded Bronze:
Cu, 84.31; Sn, 9.69; Pb, 5.92; Zn, 0.002; Fe, 0.01; Ni, 0.03; Ag, 0.02; Sb, less than 0.02; As, less than 0.10; Bi, less than 0.025; Co, 0.021; Au, less than 0.01; Cd, less than 0.001
J. Riederer
Chemical Composition: XRF data from Artax 1
Alloy: Leaded Bronze
Alloying Elements: copper, tin, lead
Other Elements: iron
Comments: All of these beads have high surface zinc, but no zinc was found by Riederer and analysis of the burr next to the drill hole on bead 1960.645.5 reveals no zinc.
K. Eremin, January 2014
Technical Observations: The patina on all of these beads is a dark brownish black, although on some a coppery metallic sheen is visible.
Each bead was cast, probably by the lost-wax method, in one piece over a clay core that was possibly formed over a rod to create the central opening. Although the internal surface is difficult to examine, the visible remains of the clay core inside the thicker areas in the shorter beads suggests that the bulging belly of the beads was also formed over a clay core and is thus not solid metal. Although the regular shapes appear to suggest that they were shaped on a lathe or with a template, this does not seem to have been the case: the beads all have relatively irregular profiles. It is also not clear that they were all originally from the same workshop. Indeed, close examination reveals differences in the way shapes are formed. Some have crisper transitions between sections (e.g., 1960.645.1, 1960.645.2, and 1960.645.6), a few seem to have mold lines, and a number of them are faceted from filing (e.g., 1960.645.2, 1960.645.4, 1960.645.5, and 1960.645.6). Whether some of the filing was done post-excavation is open to question, but certainly some of it is original. None of the beads bears visible signs of cuprite or deep corrosion, but this could be misleading. In fact, most if not all of them were electrochemically stripped. The tell-tale rough surface with pitting is clearly visible on a few of the beads—most notably 1960.645.1 and 1960.645.6. Comparison of the results of chemical and surface analyses of the alloy composition of bead 1960.645.6 (the only one that was sampled) also shows that the surface was enriched with zinc, no doubt in the course of the electrochemical treatment.
Francesca G. Bewer (submitted 2012)
