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#1
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MAP Gas Forge
Hi All
Yet another question...how hot does the outside of the forge get? I am working on my forge and I have 2" of Fibrefax blanket and about 1/8" layer of high temp mortar (like Satanite). I will add another layer of mortar of the same thickness. I fired my torch for a minute in it to dry it up a little after letting it dry for a day. The outside of the forge was fairly warm to the touch. Do i need another layer of blanket? I don't expect it to stay cool to the touch but I don't want a melt down either. I should also mention that I'm using a small refrigeration cylinder for the forge body (about 1/8" thick). Thanks |
#2
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(oops, accidentally responded to wrong thread, sorry)
__________________ Stay away from fast women and slow horses Last edited by rockhound; 09-16-2012 at 05:30 PM. |
#3
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The outside of a well insulated forge can get to 700 F, possibly even 1000 F depending on the burners and insulation. The amount of insulation only determines how long it will take for the forge body to get hot, it's the burners that decide how hot it will get. With a MAPP gas torch it isn't likely that your forge body will get excessively hot with the insulation you already have. Adding more insulation will only prevent the forge from reaching a usable temperature in a reasonable amount of time. For a MAPP forge, 1" of wool is plenty if the interior volume of the forge is small enough. Sometimes we add more wool to make the inside smaller, not really because we need more insulation. But, as I said, that just adds more mass which then requires more time and fuel to get the forge hot.
BTW, don't add more Satanite - you already have too much. The refractory should be painted on - literally, painted on water thin. It's purpose is to bind the loose ceramic threads so they don't become airborne and also add a bit of stiffness to the wool..... |
#4
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Thanks Ray
I appreciate the info as always. I'll stop where I'm at now and let the refractory fully dry. I might give it a shot of high heat paint tomorrow and then fire it up. |
#5
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A lot of us have found that an additional light coating or wash of ITC100 or bubble alumina increases the re-radiated heat back into the forge chamber (catalytic converter sort of) for a more efficient fuel burn at a lower feed rate. This also reduces a little of the heat transfer to the exterior of the forge body.
Some exterior heat is to be expected, but mostly is relative to how tightly compressed the wool insulation is on installation. A "looser" more air filled blanket will conduct a little less heat initially but over time will still give the same results. As Ray said, enough mortar/refractory. I do recommend a "hard" floor from some kiln ceramic shelving or the like. A thin 1/4" piece laid in the bottom is enough. The floor takes the brunt of the metal abuse from continual use. Mapp is pretty pricey fuel. A simple well built venturi burner will run off regular propane and get more than hot enough. My welding forge works off just one venturi burner and works very well. Have maybe $12 in plumbing parts (if that much). The needle valve and regulator are the more expensive additional parts. __________________ Carl Rechsteiner, Bladesmith Georgia Custom Knifemakers Guild, Charter Member Knifemakers Guild, voting member Registered Master Artist - GA Council for the Arts C Rex Custom Knives Blade Show Table 6-H |
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anvil, back, choose, fire, forge, hot, looser, make, paint, simple |
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