Chemical Composition: XRF data from Tracer
Alloy: Bronze
Alloying Elements: copper, tin
Other Elements: lead, iron, nickel, silver
K. Eremin, January 2014
Chemical Composition: SEM-WDS data from sample, Bronze:
Cu, 89.2; Sn, 10.7; Pb, nd; Zn, nd; Fe, nd; Ni, nd; Ag, 0.08; Sb, nd; As, nd; Co, nd
Comments: Copper sulfide inclusions.
R. Newman, June 2015
Technical Observations: All of the Geometric fibulae and fibula fragments have a green patina. 1985.35, 1985.36, and 1985.158 also show large areas of black, brown, and some red corrosion products. 1986.655 has been cleaned more than the others have. It is mostly black and brown, with small areas of green, exposed red, and bright metal. The fragmentary catchplates (1986.579, 1986.580, 1986.581, 1986.582, 1986.583, 1986.584, 1986.585, 1986.587, 1986.588, and 1986.589) are significantly mineralized and very fragile. The more complete fibulae are generally less mineralized and even retain flexibility in their pin elements.
Examining the Geometric fibulae and fragments as a group, it appears that the method of manufacture was to cast the more three-dimensional bow section with appendages that could subsequently be hammered into the flat catchplates and elongated pin sections. With designs such as 1978.62 and 1985.158, cast sections lie at two opposite sides of the flat catchplate, indicating that the hammering of the plate occurred in the middle of the casting. Some incised decoration may have been added to the cast sections (see the detail of arm of 1978.62), but most decoration is limited to the flat catchplates.
Joins between the cast element and the pins of 1985.158 and 1952.110 are visible in x-radiographs and under magnification. None of the other more complete examples, which were x-radiographed and examined with a stereomicroscope, were found to have joins at these or any other locations. The joins in these two examples may be repairs made after the pins were broken during fabrication. Presumably, the work hardening of the plates and the pins during forming would have been desirable, since it would help them to hold their shape better and would provide elasticity to the pin section. The method of production might have made the spring coil prone to breakage, hence the need for a repair join.
The main portion of the catchplate section is in most cases relatively even, usually varying by no more than 0.2 mm. The average thickness ranges from 0.5 to 0.7 mm in the group. The back of 1986.579 is not decorated and shows hammer marks related to its fabrication. It and 1977.216.3416 were the only examples not decorated on both sides.
Incised lines are mostly confined to the catchplates, but are also present on some of the arms and cast sections. They were made with a variety of pointed and flat tool shapes. All but two of the catchplates, 1986.579 and 1977.216.3416, are decorated on both the front and back sides. Incised shapes include dots, lines, circles, semicircles, arcs, and tremolo decoration. The more prominent incised lines measure about 0.3 mm in width. Many of these are curves, but even the straight lines show irregularities indicating they were drawn freehand, without the use of a straight edge. Under magnification (see the detail of 1978.62), one can see a trough that was made by drawing flat and rounded tool points across the surface, with borders of raised metal pushed up at both sides. The height of the raised borders probably varies with the hardness of the metal and the pressure applied with the tool. None of the lines appears to have been engraved or made using any other process that involved cutting and removing a line of metal from the surface.
Circular shapes were made with a double-pointed tool, with one point used to mark and hold the circle’s center and the other to inscribe the circular shape. Border designs are frequently a combination of large and small concentric semicircles. Each semicircle of the pair appears to have been made as a separate step. The inner circle of the borders on 1986.583 is faceted from drawing the line in steps, while the outer circle is smoothly drawn. Many of the circular lines vary in width through their arcs, and this effect in shorter arcs can be used to form a row of comma shapes (see the detail of 1978.62). In spite of the facets visible in some circles, their small radii, which range from 1.2 to 2.0 mm in length, make it unlikely that the tool was forced across the surface with the aid of a hammer.
Tremolo decoration (a fine zigzag pattern made by rocking a curved chisel point back and forth over the surface) was used as a border pattern (see the detail of 1986.384 belt), as a fill pattern (see the detail of 1986.655), and as a general drawing element. In 1986.655, animals were drawn with the tool used to make the tremolo pattern, giving them a soft, fuzzy appearance. The tremolo pattern appears to have been created by the rocking from side to side of a flat-tipped tool while it is simultaneously pushed forward across the surface. It may be that if the tip was slightly concave at the center, the marks appeared as two distinct rows with a gap in the middle, as in the border of 1986.384. The pattern width, and therefore the tool width, varies from 1 to 2 mm. Raised lines, longitudinal to the patterns, appear to have been caused by imperfections in the front edge of the tool. As it is pushed forward during side-to-side rocking, small, raised lines are formed, perpendicular to the zigzag incisions (see the detail of 1986.582).
The fingerprint-like pattern of the fine, longitudinal lines in some tremoli and in some of the other incised line decorations is distinct enough to match objects to a single workshop. Unfortunately, no matches were found for the objects in this group. However, the consistency in the way various tools were used to make decorations on many of the catchplates indicates that they could have originated in the same workshop or in workshops that were very familiar with each other’s working methods.
Henry Lie (submitted 2001)
