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furnace run, wootz (maybe) - Doug Ayen's Blacksmithing Blog [entries|archive|friends|userinfo]
Doug Ayen

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furnace run, wootz (maybe) [Oct. 12th, 2011|12:03 am]
Doug Ayen
I've been wanting to make up a highercarbon wootz cake, just to play with, and made up a crucible with 1kg each of wrought iron (virtually no carbon) and cast iron (iron and carbon, probably around 4%), layered with flux (glass and borax mostly), some carbon sources in the form of bone charcoal and graphite, and topped off with a ceramic wool cap. I knew the wool, which is only rated for about 2300F, would have to be sacrificed, but by then the various fluxes (glass, fluorite, borax, boric acid) should have liquified to help keep oxidation down until the metals started melting.

Before lighting off the furnace, I made a few adjustments to my burner setup -- sealed some airleaks in the blower, cleaned out some accumulated gunk from the burner port, knocked the stinkbugs out of the hoses, that sort of thing. Sealing the airleaks, I think, made the biggest difference. Last time, running full blast -- as much air as the blower could give, and enough gas that flames were only just coming out the top of the furnace -- it had taken several hours to melt a similar load, so I spent some time puttering around the shop. When I next checked in on the crucible, it was about 50 minutes later.

I could tell once I got a good look that this was running much hotter than usual. Rays-of-light emitting from the gaps in the furnace cover hot. Painful to look at hot. I shut down the burner, gas first, then air, and cracked the lid up. Before I could pivot it over, the indirect light was painfully bright. I let it back down and got some eye protection -- gold coated and didymium doped to keep out IR, UV, and .sodium-glare.

With the lid off and eye protection in place, it was a beautiful sight -- the flux was bubbling, big bright yellow spots in a mustard syrup (the cheap sutff, not the stuff made of actual mustard seed and verjuice) inside a saffron crucible, surrounded by the incandescence of the funace walls and floor.

It was clearly melted. I closed up the furnace and shut the shop down. Back's hurting a bit, I've been pretty sedentary lately, so I called it a night. I'll check on it in the morning, see if I can get the "puck" out without breaking the crucible, assuming it's cooled off enough to handle. I want to see dendrites and webbing.