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Dreamer said:
So after a few days of research and gathering materials. This is what I've got:

- 6kg high temp gas furnace kit
- Silicon Carbide Graphite crucible
- 10# Soda Ash
- 1# Cryolite
- Borax (Store bought)

My understanding is the pyrometallurgic process is basically conducting the redox reaction encouraged under heat while controlling the presence of O2. The use of cryolite appears to create HF insitu converting Si to SiF4 which is gasified taking care of the ceramic problem. The Soda Ash is the reducing agent allowing the desired metals to coagulate and stratify in the pour. The Borax prevents the oxidation of the collected metals and its weight provides a fragile transition layer( this I am deducting from what I've read).

The resulting gases are highly toxic- so proper PPE and precautions obviously cannot be overstated.

It's been 30 years since I worked with a furnace melting metals (aluminum in highschool) so I have a couple of questions if you'd be kind enough to help me with.

1) what should my first experiment be to gain some level of understanding of the process?
2) Is my basic understanding of the flux reaction and use correct?
3) Is there anything I should watch for?
4) How do you calculate the flux to material ratios?

Thank you for any guidance you can share.
Click to expand...
The cryolite is to thin the flux to ensure the metallic beads coalesce and do not freeze in the slag.
Nothing about imitating HF

Edit for spelling
 
Last edited:
Yggdrasil said:
The cryolite is to thin the flux to ensure the metallic beads coalesce and do not freeze in the slag.
Nothing about imitating HF

Edit for spelling
Click to expand...
Thanks Ygg, but wouldn't the reaction proceed including Na3AlF6(cryolite) + H+SxOx( from starting materials) -> HF + NaxOx+AlxOx +SO ? I know the stoichiometry isn't balanced but this was my understanding of the HF in situ.

Or am I just being to academic about it and I should just think of it as a thinner? Is that enough to get me started and keep me safe ?

Thanks.
 
Sorry but I don't have a lot of time to post today as I have to make a 3 1/2 hour trip (one way) to pick a friend up at the airport in Boise

So will "try" to post answers to your question tomorrow

Kurt
 
Dreamer said:
- 6kg high temp gas furnace kit
- Silicon Carbide Graphite crucible
- 10# Soda Ash
- 1# Cryolite
- Borax (Store bought)
Click to expand...

Not store bought borax. The store bought borax is hydrated, usually decahydrate or sometimes pentahydrate. Either way the hydrated borax swells up like popcorn as the water gasses off and can overflow your crucible.

Anhydrous borax is hydrated borax that has been heated to drive off the water and crushed to make it a powder again. I suppose you could make your own anhydrous borax but it would be a project for sure in smaller quantities.
 
4metals said:
Not store bought borax. The store bought borax is hydrated, usually decahydrate or sometimes pentahydrate. Either way the hydrated borax swells up like popcorn as the water gasses off and can overflow your crucible.

Anhydrous borax is hydrated borax that has been heated to drive off the water and crushed to make it a powder again. I suppose you could make your own anhydrous borax but it would be a project for sure in smaller quantities.
Click to expand...
Will get some for use in the furnace, thanks!👍👍

Is the store bought stuff still okay for little melt dish projects or just throw it in the laundry room?
 
I use it to glaze melt dish’s but it is still a bit of a pain. Use very tiny amounts and an indirect flame to spread it around.
 
4metals said:
In a small melt dish you will really see it swell up. And if you use too much it will swell over the top.

I suppose it is useable for glazing a melt dish.
Click to expand...
Yes, it’s a pain. I just hated to waste it since I already had it on hand. Thought about trying to dry it on low heat in an old toaster oven. But haven’t got to it yet.
 
Lots of people use store bought borax until they learn the difference. If you want to use it realize it will swell considerably so never fill a crucible more than half and when it swells lower the heat so it remains constant until it settles down, then heat it normally because all of the water is gone.

I don’t think a toaster oven will do it for you, for one, if I remember correctly you need 700° to drive off the water, and two, toast will never taste the same!
 

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