Brazing “Stop-off”, which is very commonly used for brazing process. Typically it’s a mixture of metallic-oxide powders, liquid carrier solution, active agents, adhesives to form a slurry or suspension.

The function of brazing “stop-off” is supposed to “stops” molten brazing filler metal from flowing into areas where it is not supposed to be, thus keeping it “off” surfaces that are supposed to remain clean, also could avoid the brazing of area which is not designed to be brazed. For example, it’s very common that the component is holding by a fixture when brazing, then the fixture should not be welded onto the components.