Some people add filing *to* consume excess O2 so what scales up is the goop that gets splashed out during a weld instead of the surface of the metal.
I once lined my gas forge with chunks of industrial coke I found along the RR, it worked great as an O2 consumer and I was able to heat treat a blade with almost no surface change.
Ground Glass is mentioned as a flux in the old smithing books.
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Thomas
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