We spent last week in the far west in a land where they speak with a lilt in their voice and I discovered several new things concerning gas and glass. I had heard that you could tell whether an LPG bottle was full or empty by weighing it, but I had never quite believed it. After all gasses must be pretty light mustn’t they? Surely it’s a bit like checking the weight of a feather. Well I had the chance to check which of two bottles was full and which was empty and found that while it was easy enough to lift one, I could hardly lift the other one. So it is true, gas can be seriously heavy. But more fascinating was what I learned watching a glass flame-worker.
Flame-work or lamp-work is an ancient method of working glass in a flame. Originally oil lamps were used but now a gas flame is used. Propane is preferred to acetylene because it is cleaner and not so unpredictable. We had a fascinating demonstration and learnt about this technique with Rob of Rogan Glass.
When heated glass will flow and try to form a sphere in the same way as a drop of water. Two pieces touched together will form a weld. If one piece is hotter than the other the weld can be snapped but if they are the same temperature they will merge and flow into each other. So a glass rod, called a punty rod, can be attached to the item being worked in order to hold it and can then be easily detached with a knock.
Rob started with a glass rod which he heated at the end which gradually formed a ball. When it was large enough he then flattened the end by pressing it onto a graphite block.
The next step was to introduce some colour by pressing a coloured rod into the flattened end. This was done half a dozen times in a circle as these were to be the petals of a flower, and then again with a different colour. Next a punty rod was dabbed onto the end so that it could be pulled into a trumpet shape dragging the coloured dabs into petals.
While working the glass Rob was wearing glasses similar to those worn by welders so that he could see what was happening in the flame. All the time he was turning the glass by twisting the rod he was holding, sometimes with both hands one holding the rod he was working and the other the punty rod which was pulling the sphere into shape.
Having watched him work on one piece we then asked him to make two for us which he did. They were then put in the kiln at a higher temperature until the colour was right and then it was left in the kiln at a slightly lower temperature so as to relieve the stresses in the glass. We went back and collected our pieces the next day.