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Black Flux

Hi all,

I have had black flux recommended to me as a great solution to
difficult soldering problems. To tell you the truth I’ve never heard
of the product. Before I search for a container of it I would like to
hear if you know of any significant safety concerns. If anyone knows
where to order it that would also be great.

Thank you,

Black flux is made by Handy & Harman and Harris Co.
( it is part number 40051- high temperature
700-1800F, and is recommended for stainless or for all metals where
extended heating times are needed. Lee

Black flux has boron compounds in it it also has fluorides in it so
you should treat it the same as most white paste fluxes i.e. have
good ventilation when using it and don’t ingest it or get it on your


Hello, Pauline:

If the black flux you are referring to is what I think it is, it is
like one sold by Handy Flux as “Type B-1”, a black paste flux designed
for soldering stainless steel and nickel silver (and I would assume,
nickel also). It probably wouldn’t be my first choice for gold or
silver work. I prefer that radioactive green colored liquid stuff
called “battern’s flux”. Both these fluxes contain fluorides, which
have been associated with health risks and require adequate
ventilation. Before I’d rush out and get the black flux, I’d call the
tech reps at Rio Grande. If you don’t have an account with them, go
to their web site and get their phone number and set one up. They
have an extensive selection of tools, findings, packaging, etc. And.
they have a broad selection of fluxes for many different applications.
Handy Flux (white) is great for silver (but contains fluorides).
Grifflux #1 flux is a past flux without fluorides, as is Solder Fast
liquid flux (for high temperature gold and silver work).

David L. Huffman

The black flux is intended for silver brazing stainless steel. It
is a little more agressive than the white Handiflux. Even for clean
stainless steel the white flux usualy is enough. Stainless steel has
a very low thermal conductivity so it is easy to overheat and oxidize
the surface. If you blacken a stainless steel surface on heating -quit

  • clean and start over. The brazing fluxes will almost always contain
    a boron compound ( borax and or boric acid) and some flouride
    compound. Sometimes they will have both type compounds. Battens flux
    is a flouride flux. The white paste fluxes are boron based. The fluxes
    are intended to keep the metal surfaces from oxidizing. The more
    active fluxes may reduce some surface oxides and float them off the
    surface but do not depend on this. Start with a clean metal surface-
    if you try to depend on the flux for cleaning you will have poor


I get my black fulx at the local welding supply.check your local
yellow pages. It is designed to solder stainless steel. Frank Goss

Dear David,

Thank you for the I use fluoride free flux for all of
my silver work and Batterns for gold. I have problems when I make
large pieces out of less than precious metals. I won’t be using it
on jewelry; unless it is on a huge piece.

Thanks again,
Pauline Weldon