ironantlerforge Posted April 12, 2009 Share Posted April 12, 2009 While building my current forge I called the manufacture of the fiberboard and blanket that I'm using to ask about expansion when heated and the guy on the phone assured me that it does expand. He added that I would have to allow for that in my designing. Later I called a company that is using the same fiberboard/blanket on a regular basis to build furnaces and industrial kilns and they assured me that it shrinks when heated. Both people gave me numbers that they where reading off of some product information chart but obviously they where not reading from the same chart. :confused: so, does it expand or contract? what's your experience? Quote Link to comment Share on other sites More sharing options...
Frosty Posted April 12, 2009 Share Posted April 12, 2009 Everything expands and contracts when it's temp changes so you need to leave a little slack so it can do so. Blanket is compressible so forget about it but board is another thing entirely. However, when you fire it it shrinks. This is not the same thing as thermal expansion, it's due to vitrification. All ceramics shrink when fired because the particles partially melt, stick together and thus take up less space. If you measure ceramics after firing you'll find they've shrunk slightly. So, yes, both blanket and board will shrink when fired but it's only evident after it's cooled back down. It will stop shrinking after it's been fired a couple times and no further vitrification is taking place. When you heat it up it will expand, every single time you heat it and it'll shrink back down when it cools. So, the answer to your questions are: Yes and yes. Frosty Quote Link to comment Share on other sites More sharing options...
Brian D Posted April 12, 2009 Share Posted April 12, 2009 Yes, the board will shrink a bit from new size after it is fired a couple times. On the forge that I just finished, I pressed the duraboard in as tight as I could get it in an effort to close all gaps. I then fired it and got it good and hot for 3 or 4 cycles BEFORE I coated the inside with ITC-100. It did shrink and expose some gaps that I pushed ITC-100 into when coating the inside. I think the blanket shrinks as well, but it is not as noticable because it is more flexible / compressible. Quote Link to comment Share on other sites More sharing options...
ironantlerforge Posted April 13, 2009 Author Share Posted April 13, 2009 very good! Thanks guys. Quote Link to comment Share on other sites More sharing options...
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