Chemical Composition: XRF data from Tracer
Alloy: Leaded Bronze
Alloying Elements: copper, tin, lead
Other Elements: iron, nickel, arsenic
K. Eremin, January 2014
Technical Observations: The fibula was originally made from one piece of metal that was cast by the lost-wax process and then cold worked in different ways to produce the final product. The bow, with the two knobs at the ends, was modeled and formed with the ridges on the back in the wax. Extra masses of metal were cast on the ends. One end was hammered out into the lozenge-shaped catchplate. The original surface of the piece is very well preserved, albeit with some pitting from corrosion. The finish is very smooth and grayish green.
Much of the border of the flat catchplate component is cracked, distorted, or missing as a result of heavy mineralization. The spiral and pin are broken off from the other end of the crescent-shaped component. There is also a deep crack at the base of the bead that serves as a transition between the catchplate and bow. A few areas of the catchplate have suffered some serious corrosion and are deeply pitted. Around the corrosion pits, the patina is slightly lighter and greener. A tan, perhaps waxy, material is in the pitted corrosion areas. Parallel, linear abrasive marks cut through some of the corrosion pits around one of the edges of the catchplate, confirming post-excavation mechanical cleaning.
The hammered sheet is remarkably thin (with an average thickness of 0.6 mm) and tapers slightly from the side closest to the bow. A variety of tooling was used to decorate both sides of the catchplate, and the tool marks are remarkably crisp. The fine lines along the preserved edges of the bow are so smooth and continuous that they appear drawn in the wax. Closer examination reveals small, repetitive stepped marks in some of the recesses that represent the short strokes with which the graver or chisel was pushed along by hammer blows, perhaps enhancing lines that had been cast. The waxy appearance of the lines suggests that the catchplate was annealed during cold working, and certainly before the metal incisions were made, in order to soften the metal, which was made hard and brittle by hammering. The band of overlapping semicircles along the edges was fashioned by a tool with a slightly wider tip attached to a compass. The center point of the compass is set into the end of each semicircle. In a few areas where the center was repositioned one can see how the semicircular tracings are misaligned and discontinuous.
The outlines of the figures and patterns on the catchplate are also incised with slightly halting lines. Tremolo patterns (a fine zigzag pattern made by rocking a curved chisel point back and forth over the surface) are present in the bodies of the animals and in the background. The blade must have had a slight nick in it, as the inscribed line is interrupted at each recurrence in the same location, creating the impression of a line. The same tremolo tool was clearly used on both sides, as the fine arched lines have identical interruptions.
The two beads at the ends of the bow and the fine ridges that separate them from the larger part were also refined in the metal. The concave part of the bow has a slightly uneven surface with some chatter marks and two uneven incisions, which may have been test incisions. The surface was scraped, which might be the result of the original chasing, post-excavation restoration, or both. There are remains of dark brown surface accretion on the concave surface, either from burial or from the original coating. On the convex side of the bow, the ridges and lines already modeled in the wax were further refined in the metal. There are no chatter marks in the lines, suggesting either that a tip was drawn along the recesses, or that the recesses were scored repeatedly until smooth. Several fine dents across the ridges were probably formed in antiquity, whereas the nearby chips that exposed the mineralized metal are later damage.
Francesca G. Bewer (submitted 2012)
