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Old 09-11-2015, 04:33 PM
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Ray Rogers Ray Rogers is offline
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Join Date: Jun 2002
Location: Wauconda, WA
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If the refractory bubbled up like that I would imagine that means you turned the forge on before the refractory had a chance to dry. Don't do that, give it a day or two to dry (depending on how thick you make it).

The hardware store stuff will work but isn't as good as what you get from hi-temp. You don't need refractory on your bricks...refractory is nothing but the same type of stuff fire bricks are made from anyway. Doesn't hurt to do that but probably doesn't help much either.

The green glassy stuff might be the refractory but it is probably the flux. My bricks don't have refractory but they do have that super hard glassy coating. Kinda makes you think twice about breathing that hot air, don't it?

Bubble Alumina is the appropriate coating for wool to make it resist flux. Note I said 'resist' and not 'flux proof'. Nothing is flux proof. If you really, really want the maximum flux resistant interior you could do as I did. I put as many fire bricks in the bottom of my forge as it took to cover the floor (3 I think - big forge). Then, I poured 30 pounds of Missou castable over the bricks - the bricks were just to take up space so I could use less castable. Smoothed that out and let it set for a week. Then I put an arch of wool over the rest of the interior. Most of the flux was on the floor so not much damage to the wool after that. But, eventually, my forge got so hot that the wool was melting and sagging so I made a 1" thick arch of castable and slipped that into the forge over the wool because the castable can take much more heat than the wool. Now, the flux puddles on the bottom where I am happy to leave it, my forge gets hotter than Hades although it takes 45 minutes to thoroughly heat that mass of castable but nothing melts except what I want to melt.

As for your forge not getting hot enough or hot fast enough, that depends on your burner and also how much mass you have to heat and the insulation. Two layers of wool take longer to heat than one layer and brick and coatings take even longer (although the ITC-100 helps hold heat for the short time it survives).

Basically, get used to the idea that welding forges need to be rebuilt periodically ...


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