How much borax?

[Everything Mac]

Hi guys - quick question

How much borax should I order to play around with welding? I'm looking at the stuff sold on amazon. Surely there is a better way to buy it?

Cheers

[timgunn1962]

Ebay?

If you search ebay, you'll get loads of hits.

There are at least 3 types of Borax. Most common is the Decahydrate, which has ten water molecules associated with each borax molecule. Then there's the Pentahydrate, with five water molecules per Borax molecule. Lastly, there's anhydrous Borax, which has no water at all.

Ideally you'd get anhydrous, but that's hard to come by. Next best is the Pentahydrate.

The first thing that will happen when you flux, is that the water of crystallisation in your Borax will boil off, making a frothy mess that dribbles everywhere and eats forge linings. The Pentahydrate has only half the water of crystallisation, so froths less than the decahydrate. A kilo of Pentahydrate also contains more of the actual "borax" bit than does a kilo of decahydrate.

[Everything Mac]

Cheers for the info mate, much appreciated.
Andy

[tenderfoot]

Im a fan of anhydrous boric acid, but YMMV. I got about 5 lbs as it was give or take $15 and i won't ever run out (though it probably isn't anhydrous anymore, but you can pre heat it in a ladle and pour it on).