What thing is that red dust?

I am seeing this video about forge welding, and it lacks of captions. Then, I can't understand a word of the speech. At minute 2:20 the smith takes a can containing a dark red dust. ¿what is it?

THANKS, anglophones!

iceng6 years ago
in Addition to Sodium tetraborate Na2B4O7 melts at 741°C (1,366°F)

Sodium tetraborate, decahydrate, Borax Na2B4O7·10H2O melts at 75°C (167°F), -8H2O, 60°C

Sodium tetraborate, pentahydrate Na2B4O7·5H2O melts at -H2O, 120°C (248°F)

Used for forge welding flux, brazing flux and a constituent of arc welding flux

Burf6 years ago
Its flux. What flux precisely is not said but I suspect that it is what most blacksmiths use for mild steel and iron; plain old borax. I think the reddish color is due to the lighting on the crystalline borax.
iceng6 years ago
It could be Sodium tetraborate Na2B4O7    melts at 741°C (1,366°F)
Used to prevent iron oxides from weakening the weld of the iron ends
into a single metal joint.