gatewood

No, but I assume, almost any sufficiently fibrous biomass would suffice. I guess the japanese used the rice straw since agricultural practices would have left tons of it as waste material.

Yes this is exactly what I was looking for. Sand seems better, since it a lot easier to get it than clay (they're both made of silicates and aluminates), my point of mixing it with wood ash, is to add potassium carbonate, which the heat will dissociate into potassium oxide, which will then reach with the silicates in sand and make potassium silicate, which will readily melt at such temperatures. Most appreciated input as well, thank you , didn't know about that function of non-oxidizing torches. You know what kind of flames are reducing? The only ones I suppose I know about, are

I was wondering, if you people know of any cheaply made ferrous alloys with a reasonable resistance to oxidation (since commercial stainless steel is way beyond the scope of homemade products). P.D: my homebrew kilns can easily melt iron and titanium.

I've seen many videos of people using borax, to protect forge welding processes from the air. Since such technique has been around since ancient times, borax wasn't there and I guess, ancient people's found a way to do it with something else. Wood ash seems like a good candidate to me, since at such temperatures, potassium and calcium oxides would form that would react with the silicates in clay, forming a thin layer of glass around the metal. You guys know of other methods of protecting metals from oxidation?