Steven Bronstein Posted September 3, 2021 Share Posted September 3, 2021 I usually use 2-3 inches of kaowool for the tops of my gas forges. I am now making a top using insboard. Since Insboard is denser can I use just 1". I am not concerned so much about saving materials, really just curious about the relative insulating ability. Thanks. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 3, 2021 Share Posted September 3, 2021 The best insulator is a hard vacuum, guess what the density of that is? Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted September 3, 2021 Share Posted September 3, 2021 Not sure that helps with his situation. I've only used fiber board on a very limited basis. However, it did seem to me that the insulating properties are impressive. I had a piece glowing on one side with my hand comfortably on the other side from where it was glowing. That was an inch thick piece, so you are probably ok with a single 1 inch piece. If you want extra peace of mind you could add a second layer, but I doubt it's necessary. Quote Link to comment Share on other sites More sharing options...
Steven Bronstein Posted September 3, 2021 Author Share Posted September 3, 2021 thanks Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 3, 2021 Share Posted September 3, 2021 Well the assumption that denser is better may not hold true. Quote Link to comment Share on other sites More sharing options...
Frazer Posted September 3, 2021 Share Posted September 3, 2021 Compare the R-values of the two materials. I'm sure they are listed somewhere. Insulating fire bricks are less dense than their hard counterparts. I guess the point is density isn't really relevant here. In many cases, less dense materials are better insulators since the thermal conductivity of air is low. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted September 3, 2021 Share Posted September 3, 2021 TP - Granted, but the question was really whether a single 1 inch layer of insboard would suffice. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 3, 2021 Share Posted September 3, 2021 Like he says---compare the R values. Quote Link to comment Share on other sites More sharing options...
Latticino Posted September 3, 2021 Share Posted September 3, 2021 Or the K values, for that matter. The real issue you will run into is that the board has a tendency to sag quite a bit over time, it is friable, and will still give off the same small fibers after being heated up to forging temperatures as the blanket. If I recall the board it quite similar to 8# density ceramic wool. You can certainly build a forge with 1" of either, it just depends on how efficient you want it to be. In either case I would strongly recommend sealing and protecting the surface. Quote Link to comment Share on other sites More sharing options...
pnut Posted September 4, 2021 Share Posted September 4, 2021 My forge uses one inch vacuum formed ceramic board coated in plistix and it works fine. It could be more fuel efficient I suppose but I have no complaints. The question you should ask is what trade offs are you willing to make. Pnut Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 4, 2021 Share Posted September 4, 2021 Sounds like I'd use 1" insboard and a thick application of kiln wash for the flame face and back it with another inch of Kaowool to boost the insulation. Orrrr, apply 3/8" of Kastolite over the board and kiln wash it for extra stiffening. The board would make constructing rectangular and square forges easier for sure. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
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