Large Air Bubbles
Probably the most common question asked on the Warm Glass
bulletin board deals with the problem of large air bubbles trapped
beneath layers of fused glass. These bubbles, which tend to be
around two to three inches across, occur in larger pieces of fused
glass (not in small jewelry or coaster items), and they first emerge
at fusing temperatures (above 1400F/760C).
Large air bubbles sometimes expand so far that they pop through
the top surface of the glass. When this happens, the popping
creates a large hole in the glass being fused, effectively ruining
Because large bubbles are most likely to form in pieces fired on
kiln-washed surfaces, firing on fiber paper will almost always
prevent the problem. However, this solution has limitations of
its own -- the back of the piece isn't as smooth, and it's more
costly than simply kiln washing the shelf. Moreover, it only
works for traditional fiber paper; it is still possible for bubbles
to form when firing over Bullseye's thinfire paper.
The next portion of this tip will discuss other
solutions for eliminating the large bubble problem.
Copyright 2007 Brad Walker.
All rights reserved.