WarmGlass.com

hi,
have made a set of coasters as a gift (float glass, 2 x 1/8) but the inclusion has created a bubble, so the surface of the coasters is not flat.

do not have time to do them again so thought to fuse them upside down ( bubble towards kiln shelf) to about 1400f/760c to flatten the bubble.

then fuse again same temperature, this time with the right side up, to fire polish and remove any kiln shelf marking from the previous "upside down" firing.

do you think this could work?

many thanks, seachange

Firing upside down will flatten the bubble and often changes the shape. It won't, of course, make it go away. You may or may not like the result, but it does at least get rid of the bulge and it won't reappear on the third firing.

Alternatively, you could drill through the piece from the top to open up the bubble, then refire face up. That sometimes helps also.

Brad Walker wrote:Firing upside down will flatten the bubble and often changes the shape. It won't, of course, make it go away. You may or may not like the result, but it does at least get rid of the bulge and it won't reappear on the third firing.

Alternatively, you could drill through the piece from the top to open up the bubble, then re-fire face up. That sometimes helps also.

Thanks Brad, I'll try it upside down. If it does not work it will be a trip into town to buy another gift

Considering it is float, do you think I need to get to 1400f/760c, or can I get away with flattening the bubbles with a lower temperature? Thinking about reducing the possible shape change you mentioned. Kiln is a large evenheat, coffin shape.

Many thanks for your advice, seachange

I'd suggest drilling a hole into the bubble add a little chip of clear or frit then refire same side up.