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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 alumina.


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 areas.


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 entire process. 


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 naturally.


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.

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Copyright 2005-2006 by M. Bradley Walker.  All rights reserved.

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