Rigidizing Fiber Board
This is part three of a
three part tip on rigidizing fiber board. Click here to go to
part one, which tells you about colloidal silica and colloidal
Once you have applied the rigidizer to the board, the next step
is to allow it to dry. It's possible to air dry the board, but
this will take several days, and it can take a week or more in humid
Drying can be accelerated by placing the board in your kiln, then
firing. Take about an hour to ramp the temperature up to
500F/260C and then soak for two hours. Make sure the kiln is
vented an inch or so; good ventilation is also essential during this
During this initial drying phase the fiber board will steam
significantly as the moisture is driven off the rigidizer.
Once this phase is complete (around two to three hours at most), you
can increase the kiln temperature to 1600F/870C. This burning
out process, which is required for all fiber products (not just
rigidized board), will yield smoke and odor, so keep the kiln vented
until the temperature reaches 1000F/540C. It's normal for the
fiber board to turn black as it heats and the binder burns off; just
continue heating and soaking at 1600F until the white returns to the
fiber board. Then turn the kiln off and allow it to cool
The fiber board will emerge from the kiln with a hard outer
shell. Once rigidized, it is absolutely essential
that the board be kiln washed before using. If you don't kiln
wash, glass will stick to the rigidized surface. You should
also take care to reapply kiln wash frequently; it won't last as
long as on a mullite shelf.
Copyright 2005 Brad Walker.
All rights reserved.
Thanks to various posters on the
Warm Glass bulletin board for information included in this post,
with special thanks to Bert Weiss, Phil Hoppes, and Graham Stone.