Theophilus: On Divers Arts otherwise known as a List of various arts(Schedula diversarum artium) or On various arts(De diversis artibus) is a Medieval Treatise detailing various recipes and techniques used in Glass Making, metalwork and painting.
Whilst the Glass Making section primarily covers furnace glass blowing and Stained glass some of the techniques can be used to inform Lampwork.
Theopphilus describes a glass ring making technique that involves using a lance like tool with a hollow metal spike sheathing a wooden handle and a disk guard. This was dunked into a pot containing molten glass removing a small amount. The tool would then be driven hard into a wooden post thus creating a ring hole. The ring would then be struck to loosen it and heated in a flame to make it more circular and by rotating it, it would decent to the disc guard.
Whilst such a tool could be used in Lampwork as I did not have any medieval examples lying around, for my first attempt I opted to use tools I already had. I used a short brass reamer I made, a solid steel ring mandrel and a stainless steel chop stick as a punty. In place of the wooden post I experimented with both a piece of scrap wood and a graphite Block.
I first formed a gather of glass around the end of the punty, then placing it against the wood or graphite block drove the brass reamer through it. It took a couple of reheats to get the hole large enough to fit over the ring mandrel. Once it was wide enough and reheated, still attached to the punty I slowly worked it down the ring mandrel to the desired size.
The rings were then placed in a pot of ceramic cooling bubbles for later batch annealing.
The Graphite block gave a cleaner result then the wood but it did scratch the graphite, leaving a rough surface. I think a steel block would work better.
This hole making technique works well on larger sculptural pieces as well as rings.
The Next step will be to try and find a better substitute for the lance like ring shaping tool tool or to make one…