[TheForge] Drying Borax (was: Welding flux?)

[Bruce .]

Well, I'm not set up to do it right now.  Only heating device I have
in my shop is a gas forge.  I bought a $2 toaster oven for the shop,
but it cleaned up so nice (!) that it's now in my kitchen.  Maybe I'll
look for another.

I stand corrected on the MP of borax decahydrate -- but that wasn't a
typo, it was a misreading of a table.  Anhydrous borax melts at about
1365 F - no mistake.  But the decahydrate "melts" at 144 F -- WAY
lower.

This changes nothing except the recommended drying temperature, which
should be less than the melting temperature.

I would be tempted to determine the minimum temperature at which the
borax would foam, then stop it while it's still foamy and friable --
easy to grind up.

On Mon, Jul 22, 2013 at 11:58 AM, Jerry Frost <akfrosty at mtaonline.net> wrote:
> Give it a try Bruce and you won't tell us again. I'd love to give you a bit
> about the 1100f typo but you have Andy for that. <grin>
>
> I worked in a soils lab for a while where drying samples is a science. Not
> the same science but it has to be done right. Hygrocopic moisture can be
> driven off at 230f. however at around 200f borax is fused into a block, it
> isn't the glassy slag of melted borax but it's mortar and pestel and elbow
> grease time. Drying in a gas oven means a minimum 230f and it turns into a
> white rock at 230f. I've tried an electric toaster oven for a prolonged
> time, 200f wasn't enough, 212f is pretty much the minimum to drive off
> moisture and 2 hours did it but meant hard grinding. I only tried a mortar
> and pestel for a really short time before getting the yard sale blender and
> even then it was time consuming, loud and beat hell out of that poor old
> blender. Were I to do it again I'd use the yard sale rock tumbler and steel
> bearings.
>
> After a couple experiments trying to dry and grind borax I started just
> melting it in the forge and using it molten. It's so much easier.
>
> Thinking about the plastic bottle I could just put a couple inches of 1/4"
> copper tubing on the end and not worry about melting it.
>
> Jer
>
>
>
> On 7/22/2013 5:06 AM, Bruce . wrote:
>>
>> I've told you guys this already, now LISTEN UP!
>>
>> Chemists dry chemicals at relatively low temperature.  I can't give
>> you an exact minimum temperature for drying borax, but I would bet
>> money it's WELL under the melting temperature of the stuff (something
>> like 1100 F!).
>>
>> Put the borax in a thin layer in an appropriate container into an oven
>> and bake it for maybe an hour at something under 1100 F.  8^)   I
>> would start with 250 F, but possibly a higher temperature would be
>> needed.  A chemist would dry to constant weight, but a blacksmith need
>> only dry till the stuff doesn't foam when placed on red-hot steel.
>>
>> Store the dry borax in a tight-fitting jar or can, as it will
>> certainly pick up moisture from the air if you don't.
>>
>> No, I haven't tried to dry borax, as I've never see the need.  I just
>> get the steel hot enough to melt the borax.
>>
>> The advantage of drying this way is that it avoids the grinding operation.
>>
>> BTW, I've got a friend who puts borax into old plastic grated-cheese
>> containers for dispensing.  Same problem with those as with squeeze
>> bottles.  But maybe somebody could fabricate a simple metal squeeze
>> container -- think of the old oil cans with the bottoms that "oil can"
>> (that's a verb, boy, that's a verb).  Or maybe get a very large old
>> oil can, clean out the oil residue, and shorten and widen the spout to
>> maybe 1" long and 1/4" in dia.  Alternatively, get a one-quart metal
>> solvent can and drill a hole in the cap.  Fill it maybe half full of
>> flux powder and use it as a dispenser -- the broad sides will "oil
>> can" to help dispense the borax.
>
>
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-- 
Bruce
NJ