Stay-Silv® black paste brazing flux is an all-purpose, high-temperature, homogenous flux for use in silver brazing. It is formulated to provide smooth flux application, even coverage, and excellent protection during brazing. The addition of boron extends the active life of the flux enabling it to withstand longer heating cycles. This makes it an ideal choice for induction brazing where intense localized heating is a factor, or heavy parts that often require longer heating time. Stay-Silv black flux is recommended for brazing copper and copper alloys, (except aluminum bronze), steel, and other ferrous base metals. Stay It is often used in brazing stainless steel, nickel alloys, and tungsten carbide. Stay-Silv black flux is used with many high silver brazing filler metals of the AWS A5.8 BAg classifications and ISO 17672 class Ag alloys. It is also suitable for use with many phosphorus-copper-silver alloys, (AWS BCuP and ISO CuP), for brazing copper to brass. Black flux turns clear, (transparent), close to brazing application temperature. This is a useful indicator in timing braze wire application.