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Stay-Silv® Black Paste Brazing Flux


Stay-Silv® black paste brazing flux 1/2 lb. jar


Stay-Silv® black 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. 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.


  • High-temperature, all-purpose black flux for silver brazing
  • Formulated for applications where the work is subjected to rapid, localized heating.
  • Ideal for applications where large amounts of refractory oxides may form
  • Used with stainless steel, carbide, heavy parts, prolonged heating cycles
  • The flux turns clear (transparent) close to brazing application temperature, indicating the best time for braze wire application
  • Used for silver brazing, including stainless steel and brazing heavy parts and carbides


Warning -

Cancer and Reproductive Harm -

Warranty Information

  • 1 Year

What's Included

  • Stay-Silv® black paste brazing flux 1/2 lb. jar



Active Temperature Range 1050F° - 1700° F (566°C - 927°C)
Alloy Type Flux
Chemical Composition Water 15-25%
Potassium Borates 50-75%
Potassium Fluorides 10-20%
Boric Acid 1-3%
Boron 1-3%
Classification AWS A5.31 Class FB3 C
AMS 3411
Federal Spec O-F-499, Type B
EN 1045 Type FH12
Color Black
NSF Compliant No
RoHS Compliant No
Shelf Life 2 years from date of manufacture
Typical Application Induction brazing
Brazing copper and copper alloys (except aluminum bronze), steel and other ferrous base metals.


Warranty 1 Year