Flux and Firescale

I preheat my pieces and spray with Stop-Ox from Rio Grande. I almost
never get firescale on thicker gauge metal and only rarely on the
thin stuff. Also, I get less firescale than I did when I started
because I don’t have to try resoldering so much-I get it right the
first time and therefore less chance of firescale.

J. S. Ellington