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Smelting Dwayne's Gold

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tomcat:
PlacerPal.....you are using a graphite crucible is there a difference between porcelain or ceramic bowls in comparison.
Have you put the insulation between the tongs and the crucible...it's hard to tell what I'm looking at in the cherry red picture.
Is there a risk of the torch blowing the gold out of the bowl...I assume you are heating the gold directly with the torch and not the outside of the bowl.
thanks for the pictures I've never seen it done.... <-good_>

GollyMrScience:
Not sure how Pal does it but I use a baby stackwall smelting furnace fired with propane for melts up to 50 oz. Larger melts need a bucket furnace and much larger crucibles -especially if dirty gold being smelted as you need room for flux. There is a difference between a smelt and a melt in that smelting is dealing with dirty gold and flux is mixed to deal with the contamination. If clean gold just needs to be melted then things are way easier.
I like the graphite crucibles if I plan on reusing them as they last way longer than silca or clay. They are also excellent for holding heat. Some fusions -depending on what is being smelted - are very corrosive on crucibles.
Many a crucible has been cut right through during a smelt if the smelt gets to corrosive. You go to pick it up and the top comes off - cut through right at the line of the melted material. A real pain.
I also pour into a cone mold and then just as the stuff gets cool drop it into water and the thermal shock will shatter the flux from the gold button.
If melting clean gold you can get away with just a borax flux and a torch if careful. Takes a fine hand to melt flux and gold at a rate that gets the gold under cover and safe from blow out if using just a torch in the crucible but I figure Pal is an experienced old hand at that type of stuff and would make that system sing.
Nice to see that clean gold Pal!!

PlacerPal:
Quote from: tomcat on September 09, 2010, 04:39:38 PM

PlacerPal.....you are using a graphite crucible is there a difference between porcelain or ceramic bowls in comparison.
Have you put the insulation between the tongs and the crucible...it's hard to tell what I'm looking at in the cherry red picture.
Is there a risk of the torch blowing the gold out of the bowl...I assume you are heating the gold directly with the torch and not the outside of the bowl.
thanks for the pictures I've never seen it done.... <-good_>


i don't have a lot of experience with torch smelting. I am more experienced and comfortable
with a Muffle Furnace and crucibles of various types.

Porcelain or Ceramic crucibles are usually used to melt precious metals, not to do smelting.
Any flux used in those crucibles sticks to them, makes a mess and is difficult to remove.

The fluxes usually do not stick to the graphite and other types of smelting crucibles. I have
large graphite crucibles but needed smaller crucibles to work with Dwayne's small amount
of gold which was a mixture of very fine gold, some flakes and a couple of pickers. With the
variety of gold in the mix, I was impressed by the portable Boilerbox Dwayne used to collect
the gold (and the Mercury). I needed the Anhydrous Borax flux to gather all the bits of gold
otherwise the small bits may have beaded up and not gathered into a bead. So it was a bit
of a hybrid operation and not ore smelting as in black sand and gold concentrates. Also
Dwayne's gold had some junk it I was unsure of and wanted to collect the junk in the flux.

Dwayne's gold

[attach=#]

There is no insulation between the tongs and the crucible. The iron tongs hold the crucible.
There is a risk of blowing the fine gold out of the crucible so we want to bring the crucible
up to melting temperature by heating from the lower sides and the bottom. As the heat
builds in the crucible, the fine borax above the gold will rise with the hot air currents as
small particles but the gold will stay below the borax. Once the borax has melted we can
direct the flame onto the borax and gold puddle. I have ceramic thermal insulation used
in building low temperature furnaces and put a sheet below the crucible in case the crucible
shatters and I lose the gold. Don't want the hot melt on the bench or into my work boot!

Oh ya, it is not a good idea to use the plain hydrated Mule Team Borax for the flux. That
borax with the attached water will usually foam up and boil the flux and metal out of the crucible.

Fine gold that has be precipitated from a leach solution would be a good example of the
type of gold we want to cover with the anhydrous borax to keep it from blowing out of
the crucible or forming multiple beads.

Fine Precipitated Pure Gold

[attach=#]

For small amounts of placer gold and even scrap gold, torch melting and smelting is a low
cost viable alternative to using a large furnace. Managing the flame of an oxy-acetylene
outfit is a bit challenging. Common propane or butane torches usually do not produce a
flame hot enough for melting or smelting although finding a torch burner with an adjustable
air and propane mix may work okay. Also apparently MAPP gas with a MAPP gas torch burner
may work okay.  

Working with the oxy-acetylene torch, flame management is the key. We don't want the flame
metal cutting hot with an oxidizing hot flame. Just want to be somewhere just above a reducing
flame (yellow) and the blue flame. The torch flame should not be "hissing" but a bit more of
a "rushing" sound. A too hot flame can erode and destroy the crucible. <-d'oh->

We are off to the goldfields to get some samples. I will do some more demos of both melting
in the porcelain crucibles and smelling black sand cons later on this fall and winter.

 :)

honeyman76:
Have fun Placerpal! And good luck! Thanks again for posting this!

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