Inclusions and Bubbles
The inclusion of material between two or more sheets of
glass has the risk of creating bubbles.
The size of these often relate to the size of the inclusion. The inclusion can be glass (powders, frits,
cut pieces), mica, metals, foils, etc.
The important element in eliminating bubbles is to have a
long slow bubble squeeze from the bottom of the forming temperature to the top
slumping temperature. If this is
combined with supports at the edges or a fine film of clear powder, it will
help reduce the interior bubbles to a minimum.
The supports at the edges may be as small as fine frit (and some use
powder over the whole surface).
But, once you have bubbles in the piece, what can you do?
You can drill a hole in the bubbles, or break the bubbles and
fuse again, but there will be distortions visible in the resulting piece.
Another method to reduce the effect of bubbles, is to flip
the piece and fire upside down to drive the bubbles to the bottom of the
piece. Be careful to use low fusing
temperatures to avoid enlarging the bubble.
At the finish, the bubble will still be in the glass but will not be
protruding above the top surface.
It may also be possible to combine the two processes. Drill a small hole in the bubbles and fire
upside down. If you do this you need to
place the glass on porous fibre paper, not just Thinfire or Papyrus, to allow
the air to be compressed out of the bubbles.
You also need to allow a significant amount of time around the slumping
temperature for this to happen.
Once you have fired upside down, you will need to fire polish the surface again. Do not despair at multiple firings. A lot of people fire their pieces many times to achieve the effects desired.
Once you have fired upside down, you will need to fire polish the surface again. Do not despair at multiple firings. A lot of people fire their pieces many times to achieve the effects desired.
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