Boric Acid / Boaracic acid is made into a paste and used alone as a flux because it melts and spreads over the metal at a low temperature protecting it from oxidizing. 7oz
A lot of metal smiths mix their own fluxes using water or alcohol and boric acid. The boric acid paste flux is generally used for vertical surfaces to hold the solder in place. For jewellery/art metal work the paste fluxes, start out either as a petroleum jelly base with borax acid added, it also can be a mixture of boric acid and gum tragacanth with a little water to form a paste.