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jmdlcar

Well-known member
Joined
Jul 19, 2011
Messages
849
Location
Ohio
Is this Anhydrous Borax Deoxidizing Casting Coarse Powder Flux the same as if I go to the store and buy Borax?
 
No - the borax (20 mule team) you buy in the store has a lot of water in it (even though it is a "dry" powder) so when heat is applied to it - it expands a great deal (foams up - as in an expanding dry foam) that is due to the water evaporating out of it as heat is applied - it works fine for glazing a melting dish &/or things like a flux for soldering or brazing solid pieces of metal

when using the store bought borax for melting/smelting the precipitated metal powders from your refining as the borax expands it will pick up some of fine metal particles & when it foams up "over the top" of your melting dish or crucible it causes those fine metal particles to fall out on to the top of your melting bench (or floor) along with the borax that foams over the top of your dish or crucible --- if you "mix" the borax "in" with your metal powders - when the borax foams up (but doesn't come over the top of your dish or crucible) some of the fine metal powder particles will melt IN the flux causing VERY small metal bead to get tied up in the flux (once the foaming has died down)

In other words - using store bought borax can/will cause "some" metal loss using it to melt/smelt fine precipitated metal powders

Anhydrous borax is borax that has had the water removed from it & therefore does not expand/foam up & is therefore preferred for melting/smelting

If you are doing a good job with your refining - & your precipitated metal powders (gold/silver) are dropped nice & clean you should not need any borax (or other flux) to melt you metal powders (other then the borax used to glaze your melting dish)

If you are needing to use flux to melt your metal powders - then you are getting a "dirty drop" of your metals & you need to figure out why your metals are dropping dirty & fix that problem so that you get your metals to drop clean

Kurt
 
I'm going to use graphite crucibles and graphite mold when I going to make my small bar of silver and maybe a round to.
 
https://www.dollargeneral.com/products/product-page.borax-all-natural-detergent-booster-multi-purpose-household-cleaner-65-oz.html
 
Borax from the market can be baked to remove the water. Baking at low heat is better because the borax will melt and stick to what ever container it's in. Borax is water soluble. Borax glass will dissolve slowly in water at ambient temps while heating speeds up the dissolution. Some people recommend adding acid when cleaning borax but I have found that you only need to add acid if the borax is heavily contaminated and pretty much black. If borax is on a button or bar, gently tap it with a flat object and the borax should chip off easily. I use the bottom of a table spoon.
 
Geo said:
Borax from the market can be baked to remove the water. Baking at low heat is better because the borax will melt and stick to what ever container it's in. Borax is water soluble. Borax glass will dissolve slowly in water at ambient temps while heating speeds up the dissolution. Some people recommend adding acid when cleaning borax but I have found that you only need to add acid if the borax is heavily contaminated and pretty much black. If borax is on a button or bar, gently tap it with a flat object and the borax should chip off easily. I use the bottom of a table spoon.

What temp should I set the oven on? How long should I bake it?
 
On the lowest setting. You can see the reduction of volume as the water is driven off. There wouldn't be a set time. It depends on thickness of the layer. A thinner layer may only need a half hour after the oven is warmed and a thicker layer may need an hour or more.
 
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