Chemical Composition: XRF data from Tracer
Alloy: Bronze
Alloying Elements: copper, tin
Other Elements: lead, iron, silver, antimony, arsenic
K. Eremin, January 2014
Technical Observations: The patina is mottled light green, with olive brown and dark gray spots in the more preserved areas of the surface and reddish yellow in the corrosion pits.
The mitra was made from a sheet of bronze that was formed by hammering. An x-radiograph of the object shows a broad, mottled pattern of hammer marks that runs parallel to the top edge. X-radiography shows that the metal is of relatively even thickness overall but is much thinner at the lines that correspond to the decorative ribs. The ribs appear to have been created by pressing or drawing a smooth-pointed tool along the back surface of the mitra. Numerous finer lines are visible in several of the grooves on the reverse of the ribs, evidence that these were created through repeated pressure with the tool. There is no evidence of hammering or punch marks that can be connected with this tooling. Discontinuities and areas where the tool slipped are very clear in the x-radiographs. The ribs are enhanced on the front surface with finer incised lines.
The rounded top edge of the mitra was formed by bending it outward, probably over a wire, and the edges of the rounded section were rolled inward over a finer wire, much like the other mitrai in Harvard’s collection (1). The wire is probably made of rolled copper alloy sheet. In this case, the wire is not visible in the x-radiographs, but the dark brown terminus of a wire, perhaps made of iron, emerges from the worn or broken end of the lower, curving edge.
The holes along the top of the mitra were cut through the decorative lines after they were formed. The rings in these holes were too dense to be penetrated by the x-rays, but they are probably hollow and formed from rolled metal wire. There is no weld at the join where the ends meet.
Most of the metal surface on the front of the mitra was originally highly polished, although restoration may account for some additional smoothing. Closer examination under the microscope shows a fine dendritic structure in many areas, which is evidence that the sheet was cast. The back surface is almost entirely obscured by corrosion and burial accretions. The green corrosion material comes off in powdering flakes, revealing a smooth black metal surface.
NOTES:
1. For additional mitrai that are thought to be related to Harvard’s group, see H. D. Hoffmann and A. E. Raubitschek, Early Cretan Armorers (Mainz, 1972) esp. 10, 20, and 54-56.
Francesca G. Bewer (submitted 2000)