Roman Glassmakers Newsletter 4: July 2002

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Rods, Canes and Florets (1)

The processes described here are those we use for making the more developed canes found in early Imperial composite mosaic glass as discussed by Grose*. Earlier forms of canes require additional techniques, and will be covered separately (see Newsletter 5). (We are aware of the danger of categorising rods and canes too rigidly: there is a certain amount of overlap. For instance, several 'patellae' we have seen include the much earlier spiral-pattern cane cross-sections and a hemispherical bowl illustrated by Grose* (No. 186) includes cane cross-sections of a concentric pattern.)

*(D. F. Grose (1989) 'Early Ancient Glass' New York: Hudson Hills Press (ISBN 0-933920-92-X))

Definitions:


Cane Types:

Floret with concentric ring pattern Floret with concentric ring pattern Floret with multiple spot pattern Floret with spoked wheel pattern Floret with spoked wheel pattern

There are three basic types (examples above): those with concentric rings, those with many tiny rods dispersed in the matrix and those with a pattern resembling a spoked wheel, elements of each of which can be combined to form hybrids. Concentric patterns are the simplest to make and involve repeated gatherings of coloured glasses to build up the pattern. The other two types, and any hybrids (examples below) have to be assembled using component rods.

Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern Floret with hybrid pattern

Rod and Cane-making:

All of the processes described below can be performed by one person working alone.


Annealing rods and canes:

After being made all canes and some rods require a basic annealing. We find that placing them in a hot kiln (570°C) which is turned off at the end of the working period is sufficient, since they do not need a full annealing cycle. Thin single colour and bi-colour rods do not need to be annealed at all, but thicker bi-colour rods, particularly those with a thin outer coating of opaque glass, do. The annealing cycle allows the fabric of the glass to relax without distorting the shape of the glass. This removes the possibility of the glass cracking due to stresses. Complex canes prove difficult to break into florets if not properly annealed.


Florets:

Once the canes have annealed and cooled they are ready to be cut into florets. There are several ways to do this: Lengths of notched canes The notches act as 'crack-starters', and guides for the next procedure:

The angle at which the cane floret sections are cut is important. There is evidence on original vessels which shows that canes were deliberately cut at an angle. The flat areas of composite mosaic plates show florets sloping at angles which cannot be explained by movement of the glass during a slumping process. Cutting florets at an angle of approximately 60° will allow the sections to overlap during assembly of a disc, cutting down on the size of gaps between the canes. This helps to speed the fusing operation.


Speculations on assembling canes the Roman way:

Nowadays it is a simple matter to wire bundles of rods together for heating and fusing. Wire may not have been so readily available to ancient glassmakers, so it is worth considering other methods of cane assembly.


Mark Taylor and David Hill


vitrearii @ romanglassmakers . co . uk 0044 (0)1264 889688

Unit 11, Project Workshops, Lains Farm, Quarley, Andover, Hampshire SP11 8PX, UK

This Newsletter is now being archived on the website for the British section of the AIHV: www.historyofglass.org.uk

You can also visit us at: www.project-workshop.co.uk

Our website is revised regularly. A recent addition covers the subject of our reproductions of mould-blown beakers from the 1st century AD. www.romanglassmakers.co.uk

Mark and David