Glass Beadmaking - The Raw Materials
I promised you some insight into lampwork bead making so here is where it all starts, with the glass. As you can see from the picture the glass comes in rods of different colours, transparent and opaque. It is generally about the same thickness as a pencil. You can hold one end of the glass while melting the other end as glass is an insulator and the heat doesn't travel up the rod.
There are two main types of glass that can be used for bead making, borosilicate (pyrex) and soda lime.
Borosilicate is a very stable glass which does not expand or contract much when heated. However it needs to be worked at a very high temperature. Many of the colours are not as seen in the rod but continue to develop once they are out of the flame in the kiln for annealing (I'll talk about that another day). I have had a few goes with boro but for Christmas decorations rather than beads.
Soda lime or soft glass is my glass of choice. There is a huge range of colours available. Most of the colours will end up looking just as they do in the rod although there are an increasing number of reactive or silver glasses which can change appearance depending on the mix of oxygen and propane in your flame.
There are different types of soda lime glass. The important thing is that you select glasses which expand and contract at the same rate. If you don't and you combine them, then when your bead cools the different glasses will cool at different rates and your bead will crack. I generally use glass with a coefficient of expansion (COE) of 104. That includes Effetre the well known Italian glass used on Murano, as well as Reichenbach and Lauscha from Germany, CIM and the reactive glass from Double Helix in the USA.
I have used other makes of glass which can't be combined with the 104 family. Bullseye is another make from USA which has some lovely colours. It is a little stiffer to work than the 104 family having a COE of 90, and that can be useful at times but it's main attraction is some of its lovely pinks and opal colours that you can't find elsewhere.
There are other types of soft glass with COE of 96. I have occasionally used Gaffer or Uroboros but I have generally only used the clear rods when I want to use a lot of frit. Frit is small fragments of glass used to decorate the surface of the glass or encased within clear glass. It is generally made from intensely coloured furnace glass which has a COE of 96. You can use it with the Effetre (104) glass and the Bullseye (90) as long as you don't use too much. If you want to use lots of frit, especially if you want to encase lots of it in clear then you may need to change to a glass in the 96 COE family. Some colours are trickier than other, reds in particular, but it can be a bit trial and error.
Next time I'll talk about some of the other materials that can be introduced into the glass as part of the design.