Reinventing Laffitte welding plate

Looking to reinvent Laffitte welding plate that was sold over a
century ago and it apparently made forge welding a cinch. It was a
sheet of low-carbon iron mesh impregnated with anhydrous borax and
iron filings. It was slipped between two hot pieces of iron and the
joint was simply hammer welded closed. I’m trying to figure out what
binder might have been used that didn’t hydrate the borax or oxidize
the iron, so I was interested in the term “paste” that you used re
the Centaur forge welding flux. Do you know what the paste is. Do
any readers have more info or suggestions?

Looking to reinvent Laffitte welding plate that was sold over a
century ago 

Interesting quest. Laffitte sounded french to me, so I googled a bit
in that direction.

Here’s a link to old french publicity of the Laffitte company:
http://bit.ly/cy1gLO

Googling further using the formal name of the company, “Societe des
plaques et poudres E0 souder”, brings quite some
especially Google Books has some in different languages, among the
french and US patents.

They obviously also had a welding powder that was spread over the
already red-hot metal which were then, again, hammer welded to join
the pieces.