Rigidizing Fiber Board
Rigidizing (or rigidising) is the process of treating fiber board
so that it becomes more rigid. This helps the board last
longer and helps keep the surface from deteriorating or becoming
pock-marked. Rigidizing also helps keep dust down so that
there are fewer airborne fiber particles. Whether or not
rigidizing is appropriate depends on how you want to use the board,
but in general the more the board will be handled (such as using it
for dam material) the more likely you will want to rigidize the
The major ingredient required to rigidize board is a liquid
hardening product such as colloidal silica or colloidal alumina.
These can be purchased directly from refractory suppliers, either by
their chemical name or by the name of "rigidizer." They may
also be purchased from some stained glass wholesalers under the name
of "Fiber Mold Hardener." These products separate and are
ruined if frozen, so it is sometimes difficult to obtain them in
Although colloidal silica or colloidal alumina can be used to
rigidize fiber board, there are some differences between the two
products. While a respirator is advised when using either
product, colloidal alumina has the advantage of not containing
silica, so it is a bit safer to work with. Colloidal alumina
also tends to make the board a bit more rigid and less likely to
stick to glass. And finally, colloidal alumina is more
expensive than colloidal silica (about double the price!); for this
reason most generic "rigidizer" or "fiber mold hardener" products
are composed of colloidal silica.
Click here for part two of this tip, which details
the process for using these products to rigidize fiber board!
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.