This Ronda Coryell masking mud is an anti-fusing agent that helps ensure a crisp, clean fusion of metal parts when soldering or fusing them together. The mud protects the metal adjacent to the area to be joined so that the joint is precisely—and only—where you want it. The mud also serves to prevent the adjacent metal form or structures from distorting under the heat of the soldering/fusing flame. Masking Mud is ideal for use with Argentium™ Silver. Apply flux first to the area to be joined to help pull the mud into detailed areas, then apply a thin coat of the mud to areas that you do not want to fuse or solder. After your workpiece cools, easily remove the masking mud with water and a soft brush, then pickle. This masking mud works well for gold, silver and non-ferrous metals. Made in the USA.