Smelting

[ChopperGreg]

Cryolite is not a flux for aluminum - it is a flux for alumina - alumina is an oxide of aluminum - it is VERY hard (just under the hardness of diamonds) & VERY chemical & heat resistant

What I intended to say before my brain ran past my typing fingers was:
...normally considered as a flux for making aluminum

not
...normally considered as a flux for aluminum

Though it (ceramic/alumina) is VERY chemically resistant - both hydrofluoric (not hydrochloric) acid & sodium hydroxide will react with it so will etch large pieces of ceramic &/or dissolve it if it is ceramic powder --- in other words hydrofluoric acid & sodium hydroxide are both solvents for alumina/ceramic

...snip

I use it for smelting ceramic capacitors (after milling to fine powder) - BUT - because cryolite is a flux/solvent for ceramics in smelting it is also hard on (shortens life) of crucibles - so you want to use "good" quality crucibles & not cheap "budget" crucibles

I have been considering using lye and cryolite to deal with MLCCs, to try and avoid the roasting and crushing steps, as I have some neighbors that will complain if they think even a lawnmower has been running to long

to clarify - cryolite is a flux ingredient added to other fluxes - starting with the basic fluxes of borax & soda ash - plus other fluxes - based on what else is needed for the smelt (such as fluorspar, silica, carbon etc. etc.)

No issue with borax, for the final melt and pour of individual metals.
My issue with borax is that it binds with metal oxides a bit too well for the initial melt and pour, where I want to retain several of the base metals if I can.
Copper is my collector metal of choice, and I want to keep recycling it, but I have uses for even zinc, and a few others, if I can retain them.

Like it doesn't take much fluorspar in you flux to thin slag - it doesn't take much cryolite in your flux to dissolve/slag off the ceramic --- as with all things smelting - it's a bit of a learning curve to figuring out how much &/or what flux ingredients are needed in the particular material you are smelting

Cryolite is also used as a glaze for making pottery so that is a source for where it get it

I have not tried this yet - but because cryolite works as a flux for ceramics I have thought about trying to use it as a flux for smelting black sands as it may (or not) also work for slagging off the iron oxides that make up black sands ???

Kurt

I believe Cryolite and Flourspar are more or less interchangable.
Flourspar are easier to find I think.

Fluorspar is an easier to obtain version of cryolite.

More than anything else, I noticed that fluorspar in the form of calcium fluoride, was twice ( or more ) the cost of cryolite in the of sodium hexafluoroaluminate, on eBay

If push comes to shove, I know a natural source of fluorspar, in the form of low grade fluorite, about 45 minutes from the house, that I can collect if I need to.

 

[goldshark]

See, when I've used that much carbonate, it just bubbles. I'm pretty sure it's eating the wall of the crucible.

Are you using Sodium Bicarbonate, or Sodium Carbonate? Sodium Carbonate can be made by roasting Sodium Bicarbonate in an oven at 400 F for a couple hours. Let cool, with an Aluminum foil cover wrapped fairly tight so as not to re absorb the driven off CO2. Store in an air tight container. The roasting/conversion of SB to SC is performed by driving of CO2, which shows up in the crucible as boiling (driving off more CO2). Some people use Sodium Hydroxide flakes to almost entirely eliminate boiling. If you think the Carbonate is eroding your crucible by boiling, check your crucible after your first pour. If it is eroding, add some fine Silica sand. Start with100 grams per pound of concentrates, check crucible for erosion. If erosion continues, add more, until crucible erosion stops.

 

[Nountaineer]

Ouch, buddy always change eBay first. Education costs Time and Money, but I bet you are a lot smarter now.

It arrived Friday and is 2.5 kg, not pounds and is 98.5 percent. I will save it for a rainy day and will use the 95 that I also ordered. The crucible was eroded

 

[snoman701]

Are you using Sodium Bicarbonate, or Sodium Carbonate?

Soda Ash, Sodium Carbonate

 

[Nountaineer]

Fluorspar is one of those ingredients that depends on what you are smelting. Some
Mixes use a small percentage amongst other ingredients and for thick viscous slags you add more. The end result is a thin slag that does not hold up beads.
But be wary of overuse. It eats crucibles so notice the ring it erodes and when the crucible wears too thin (which you check every time you put a smelt into a crucible) use a new crucible.

Can you also tell me what to do besides heating the crucible to 2000 degrees for curing. I did not have any whiting to treat it with. It is cooling off now.

 

[goldshark]

Soda Ash, Sodium Carbonate

Sodium Carbonate can absorb CO2 from the atmosphere, if not stored in an air tight container, after opening the bag. This changes it back to Sodium Bicarbonate. I put mine into a 5 gallon pail(s), with good sealing lids, once the bag has been compromised. Smaller Mason canning glass jars, properly labeled, for daily use. If it has been exposed to atmosphere, baking in the oven will remove much of the CO2 again.