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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 surface.


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 winter.


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.

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