I’m about to try some jewelry cabochons in some casting molds using my glass blowing frit and based on the texture of the bottoms of my fused and slumped projects, I’m guessing the finish on the top of the cabs won’t be totally smooth and shiny. Do you generally fire polish the cabs after fusing?
Firing polishing cast glass can be tricky, depending on size and shape. The trick is to get to fire polish temp as quickly as possible (once past the risk of thermal shock) to allow the heat to “wet” the surface without penetrating the glass sufficiently to cause it to deform.
Cabochons, because they have rounded surfaces (not a lot of surface texture detail) should fire polish easily. Temperature will vary depending on glass and speed at which kiln heats. Try 1375 F to start and adjust accordingly.
If you have some polishing bits on your grinder or some diamond hand polishing sponges you could pre-polish them a little bit and than they will fire polish at an even lower temperature. Around 1300 F.