"In damascus won't it add a lot of silica? seems like a potential issue."
Silica is what makes wrought iron have its pattern. Unless it is used to excess, a very fine powder should be OK.
The Japanese smiths use rice straw ash as flux when doing the folding to create hada. It is alkaline with about 70% silica.
An old Western forge welding flux used by blacksmiths is basically charcoal powder, lye, saltpeter (or a mix of borates/nitrates), and finely ground feldspar. I think some blacksmith supplies sell a similar mix as magic weld or miracle weld.
A similar mix without the feldspar is used for casting flux.