Only Gilsson created opals are able to be used in glass. Any other opal will burn out or just fail.
There are many ways a blower will make tubing.
Crushed opal tubing with frit
- Heats up a slug of glass
- Drop in the crushed opal and let it stick to the glass.
- Drop-in some frit to have the opal end up layering in between the glass slug and the frit.
- Melt it down and you have some crushed opal tubing
Crushed opal sleeve
- The blower prepares an open-ended slug, usually 45mm or 50mm and leaves it in the kiln till later
- The blower makes a colored tube.
- The blower lays down some crushed opal in a frit tray and rolls the hot colored tubing in it, having the crushed opal stick to the colored tubing.
- The blowers insert this colored tube with opals into the pre-opened slug
- The blower then sleeves the colored/opal tube with the open slug
- When done the blower has a tube of colored/opal tubing with clear glass on the outside.