Question About Borax Flux

Is there any difference between borax flux and plain old borax from
the supermarket ? Can I just resurrect The Old Ranger and buy some 20
Mule Team Borax for casting ?

Brian Corll
Vassar Gems

Is there any difference between borax flux and plain old borax from
the supermarket ? Can I just resurrect The Old Ranger and buy some
20 Mule Team Borax for casting ? 

Yes borax from the grocery store is the same compound and it is
useful as a flux. However many commercial fluxes use other compounds
in addition to the borax to lower the melting point and extend the
working time but it works fine for most jewelry type metal casting
operations. Not really useful as a soldering flux due to its high
temperature melting point.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts

Brian,

The 20 Mule Team Borax works great mixed with water as a flux when
soldering and can be used for casting as well but the Borax you buy
at the tool supply houses is a much finer grain and is a better
choice for casting.

Greg DeMark
greg@demarkjewelry
www.demarkjewelry.com

I cant say if its chemically the same, so if the scientists in the
crowd want to chirp in no offence will be taken. We used 20 Mule Team
as casting flux for years, and don’t remember any problems. Other
than you couldn’t always find it at the store. Its not bad for
cleaning up the shop and dirty polishing aprons either.

Christopher Arnett
www.christopherarnettjewelers.com

Jim,

I have been using 20 Mule Team Borax mixed with water as my only
soldering flux for over 25 years and have never had a problem with
it.

I do use the finer grade commercial Borax as my flux for casting.

Greg DeMark
greg@demarkjewelry
www.demarkjewelry.com

Ben using for years in the shop also when brazing the kids toys,
wagons treks etc. learned it from an old welder back in the 50’s

Don in Idaho

Well, my wife came home with a big (and I mean BIG) box of 20 Mule
Team Borax when she did her shopping. So I guess I now have lifetime
supply of borax flux. :slight_smile:

Brian Corll
Vassar Gems

Hi Greg,

I have been using 20 Mule Team Borax mixed with water as my only
soldering flux for over 25 years and have never had a problem with
it. I do use the finer gra.de commercial Borax as my flux for
casting. 

It is not that borax alone will not work, it was used for ages as the
only soldering flux and is of course still used today as you point
out. It is just that it has a fairly high melting point at 1367F.
Most commercial soldering fluxes melt at lower temperatures (about
1100F) and they offer a greater range of protection by having more
fluxing ability, being more fluid and having a reduced surface
tension.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts

I have been using 20 Mule Team Borax as a high tempature flux for
some time now. I use it for brazing work. Works well with steel. Also
works well when fusing or brazing copper items. I started doing this
after watching the blacksmiths use it as a flux for forge welding.

I have also used it as a flux when casting bronze. No problems so
far.

Bill Churlik
@Bill_Churlik
www.earthspeakarts.com