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Commentary to Lierke/ Birkhill/ Molnar 1995, Experimental reproduction of spiral beads.

The background of this paper: Julian Henderson had explained the manufacture of a special kind of spiral beads in J. M. Coles,ed., Meare Village East. Somerset Levels Papers 13, 1987. His explanations included the possibility of moulding, ‘sharpen-up’ extremely tight spirals by cutting, subsequent filling the spirals with glass, final grinding and polishing. His theories did not convince the authors - all of them with many years experience in glass working. In their paper ‘Experimental reproduction of spiral beads’, they proposed and experimentally verified two different methods, both avoiding intermediate reheating, cutting, and polishing. In the Lejre book, their paper appeared with a 5 point response by J. Henderson, who defended his theories.

Here are 5 points, defending the proposal of the three authors.

1. It is true that any manufacturing theory must remain hypothetical unless evidence of the process is found. However, many years of practical experience, supplemented with private studies of ancient glass objects, are a sound foundation to recognize the stumbling-blocks of a theory. The statement that some enigmatic objects must be bead moulds is no uncontested evidence.

2. An experienced bead maker is able to fabricate wound beads in ‘closely similar or exactly the same dimensions’ without a mould. Half moulds are required today for the speedy production of precise shapes. Closed two-part or three-partite moulds for the making of grooved beads - theoretically(!) prepared for the inlaying of chevrons or spirals - would only be required for exactly identical shapes and patterns. But, mould seams have not been found. The beads show varying shapes. The spirals show different numbers of turns, distances, or interruptions. Unequivocal evidence for the use of patterned moulds therefore is missing.

3. The assumed ‘pouring’ of glass into a small bead mould would not be possible, and not produce a bead with prefabricated grooves. Glass needs pressure or vacuum to comply to a patterned surface. It would still be difficult with modern precision instruments to engrave (or ‘sharpen up’) exact spiral grooves with some ridges only 0.015 cm (!) broad. A fused powder fill would show numerous bubble holes after cutting and polishing. - But, the winding of a glass filament around protrusions, as proposed in the paper of the three authors, is well supported by many examples. Protrusions disappear through prolonged heating. No marvering is necessary. One example of the Meare beads (G 45, p. 83) shows protrusions which were only partly melted down. The cross section of the grooves after trailing the decor and rounding the bead depends on the relationship of the viscosity of the two differently colored glasses. This cross section naturally is always u-or v-shaped.

4. Flat facets around the bead holes are found also on Venetian beads where they result from wear. Other explanations are possible. For instance, a flat spot may be generated by an instrument during the removal of the wound bead from the rod, or by hitting a flat surface while the bead is still soft.

5. Henderson mentions experiments, but he failed to show the results for comparison.