Glass used by artists to fuse in a kiln, or work in a flame, is made all over the world by many different manufacturers. For example, Germany produces, among others, Reichenbach glass rods for beadmaking. China produces CIM, America, Bullseye, and Italy Effetre.
I use all of these when making glass beads.
For my fused projects; bowls, hearts, framed pictures, I use Bullseye glass. It is made by hand in Oregon, USA, but is available in the UK. Even before arriving in my studio, where it is cut, shaped, melted and re-formed into objects of art, the glass has undergone a rigorous process of being formed.
Bullseye glass is made from a combination of sand, soda and lime. Glass can be made with sand alone, however, adding the soda and lime, means that it can be melted at a much lower temperature and is more durable, making it accessible to people like me to fire in a small kiln in my studio. The glass is coloured with metallic oxides, such as, cobalt to make blue and chrome for green. Some of the more exotic colours, such as pink and rose have gold or even rare herbs added.
The ingredients are carefully weighed and then mixed in barrels for two hours before being transferred to a furnace, where it is stirred, by hand. After sixteen hours in the furnace, the glass is removed, by hand, with a steel shovel. The molten glass is quickly placed onto a water cooled table where it is rolled into a sheet. The sheet is hand carried on a lightweight metal plate and put into a 100ft annealing oven. Here it moves slowly through the oven, and gradually cooled until it reaches room temperature.
Each sheet is carefully inspected for colour and quality. A second inspection is carried out to ensure compatibility. Every sheet made by the manufacturer must be compatible with each other, to ensure it will expand and contract at the same rate when heated in a kiln or flame. If it is not compatible, stress occurs in the glass and it can crack or shatter.
At the end of this process, the glass sheets are ready to be distributed and sold to glass artists all over the world.