This is a suspension of 188 solder powder in an active flux compound. In industry, it is used for tinning steel. To use, clean both surfaces and apply a thin smear of paint to one side or else they can be dipped. The joint is then assembled, held and heated until the solder melts to show a silvery line through the black flux residues. Hottape and Solder Mask are particularly useful with solder paints and creams. When you open the jar, there will be a clear liquid on top of the solder. This is the flux. Be assured, we have not watered it down! Solder powder is obviously much heavier than the liquid flux, so before using, be sure to give it a good stir. It is also a good tip cleaner.