Flux Solid Block
Tallow is a natural flux for use on lead came in leaded window work. Stained Glass artists have been using tallow for centuries to flux their solder. Simply rub a little tallow onto your lead joints prior to soldering to help it flow and stick. You can also use a small wire brush on your stained glass panel to help clean the lead before application which lets the tallow help your solder flow and adhere.