My old boss was pretty "old school". We used straight up Borax and
water at work for Bronze pellet and silver alloy filler brazing. For
small stuff maybe not the best flux. Still, it worked. He built quite
a few trombone bells using Borax as flux.

One trick I was taught, was to warm up the borax/water solution on the
work with the torch til it starting "foaming" to a white bubbly
finish, let it rest, hit it again with torch til it settled down a
bit, then add the filler. Or in the case of a seam, do that process,
then heat work up to point of brazing. (pellet was mixed into the
Borax and laid as a bead prior to applying heat)

Neil.

On 6/15/12, David Beierl <dbeierl@attglobal.net> wrote:
> At 03:55 PM 6/15/2012, neil n wrote:
>>And speaking of DIY flux, one can use Borax for silver brazing flux!
>
> Ordinary powdered flux for "bronze" brazing is
> largely borax, but silver-brazing flux is a lot more complex (and nasty):
>
>>Silver-brazing fluxes contain boric acid and
>>potassium borates, combined with complex
>>potassium fluoborate and fluoride compounds.
>>Fluorides, up to 40 percent in flux content,
>>give these fluxes their characteristically low
>>melting points, 1,050� F. and high activity for
>>dissolving metal oxides. Silver-brazing fluxes
>>that contain elemental boron offer improved
>>protection on carbides and on materials that
>>form refractory oxides such as chromium, nickel, and cobalt.
>
> ;-)
> d
>
>

-- 
Neil n

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