Firing cremains to avoid bubbles

Firing with cremation remains is very similar to firing with any organic material encapsulated into glass.

Design

There are several possible design approaches.

Drilling holes is one method to avoid bubbles.  You can drill the base, put the remains on top and then cap.  Place the whole assembly on 1mm fibre paper to allow the air to migrate out through the hole and fibre paper under the glass.

Alternatively, you fire upside down and then fire polish the top.  Place the eventual top down onto the kiln washed shelf or Thinfire. Place the remains on the glass and cap with the glass that has the hole drilled.  Fire, then clean, turn over and fire polish the final top surface.

Design the piece and placing so there is a gap at the edge. 

This gives a route for air to escape.  If there is any gap left after fusing, it can be filled with a bit of super glue or other clear glue. 

Another method is to place pieces of frit or stringer at the very edge of the base glass to allow air out from under the centre of the piece.

If you do not need to concentrate the cremains in one area, you can disperse the material evenly across the piece to reduce the possibility of large bubbles.  The air and gasses can migrate to the edge through the particles, just as happens with powder sprinkled between layers of glass.

You can combine some of these methods as they are not mutually exclusive.

Firing

Fusing these pieces is, in principle, the same as encapsulating any organic material within the glass.  Slow advances are required with a 3 to 4-hour soak at around 600°C to burn out any residual organic material just as you might for thick vegetable matter.  You can add another bubble squeeze soak of an hour or so at around 650°C to gradually push any remaining air out from between the particles.  Then advance to the fusing temperature and anneal as usual.