20 Mule Team Borax

Hi everyone. I was wondering if the borax in the box of “20 Mule Team
Borax” in my pantry is the same as the borax that is used as an
antioxidant and flux for melting precious metals. I was going to buy
some borax, but want to know if I already have some I can use. I
wonder if what I have might contain additives that would make it a
bad idea to use for jewelry making. Anybody know for sure?

Gail Middleton

Dear Gail, I have been using the 20 Mule Team borax for a casting flux
since 1971. I’m on my third box purchased right from the grocery
store. I would never change to any processed box of casting flux. I
use it for spin casting as well as electro melt vacuum casting. Never
had any problems.

Best Regards,
TR the Teacher & Student

Gail: maybe others have more detailed but yes you can use
it, I use it to coat my crucibles for casting. There are casting
fluxes that probably work slightly better but go ahead and use it, it
IS borax! Dave

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The “20 Mule Team” you buy in the store is (as I understand it)
pretty much just scraped up in the desert borax mines, sticks and
stones removed, and sold. So it does doubtless contain some
impurities, but just what they are and how much will probably vary
from box to box, and certainly from manufacturer to manufacturer. And
there’s probably no way of finding out. I would imagine the borax used
in flux may be a bit more pure, but don’t really know for sure.


Hi Gail,

I’ve never seen a chemical analysis to 20 Mule Team, but I’ve been
using it for years with no bad effects. The only caution on the box
says " Contains sodium tetraborate decahydrate. Avoid contact with
eyes. Do not take internally."

The only other info on the box says, “Borax is a naturally occurring
mineral composed solely of sodium, boron, oxygen and water.”


Laundry Borax, including 20 mule team, works just fine for all these
uses. Some brands include some little blue bleaching agent crystals,
but these are a very small proportion of the total chemical, and don’t
seem to affect the products effectiveness as a melting flux or
component in fluxes (prips, etc.).

Peter Rowe

Dave, do you have an address on the box of 20 Mule Team? I’d like to
contact them inasmuch as I can’t locate a store here that sells it.

Hi Gail, Yes, 20 Mule team, Ronald Reagan, Death Valley Days Boraxo
is THE stuff! (I’m aging myself of course) you don’t need a lot, just
a pinch will do. J.A.

Margaret has it right. Same stuff, but 20 Mule Team isn’t as refined
as lab grade, but works plenty well for casting flux. If you’re making
a spray-on type of flux, you may want to use the more refined grade,
because it’ll dissolve better with less impurities. Unlike casting
temperatures, soldering won’t get as hot to bring impurities floating
to the surface where you can pick it up with a rod.

When I was interested in making Pripp’s solution, I posed the same
question to the company that makes 20 Mule Team (I’m traveling and
don’t have the box to refer to!) who informed me that it is exactly
that, pure Borax with just an insignificant amount of impurities. So
feel free to use it for the purpose you stated. By the way, my
Pripp’s turned out just fine when I used 20 Mule Team, and I’m sure
it is great for killing roaches, too! Susan.

Concerning 20 mule team borax: Borax minerals are either mined (US
Borax at Boron ,California) or solution mined (Searls Lake ,Ca.) The
borax minerals are : sodium borate ore =Na2o. 2B2o3 .10 h20 these are
dissolved in water and impurities such as salt (NaCl) and sulfates are
crystallized out. The borate solution can be dehydrated at red heat
to yield anhydrous borax (Na2B2o3) which is essentially sodium
metaborate. Reference the Rio Tinto.com website. They are the present
owners of the California Borax operations. Other materials comes from
Death Valley (Furnace Creek and Panamints). Happy to supply a
Geochemically correct response.

Hi, The name on the box of 20 MT I have is: The Dial Corp., Phoenix AZ
85077. No other address info is present.