# Flux Recipe needed



## oldgeek (Dec 8, 2010)

I would like to recover values from a small collection of broken melting dishes and micro furnace parts. 

I have found a link to a flux recipe Harold posted that i believe would work, but the link is broken. 

Does anyone have a recommendation as to what i should use?

I plan to pulverize the scrap, mix well with the flux, melt it in a furnace i am building, then pour it into either a cast iron cone mold, or a home made cone type mold.

I also have some magnesite cupels i would like to recover values from. The cupels were NOT used with lead, but a mix of bismuth for the purpose of refining. Could i use the same method to process, or should i try to grind the top surface only to cut down on the amount of material i have to deal with?

Thanks
Scotty


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## lazersteve (Dec 8, 2010)

Where is the post with the broken link at?

Steve


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## oldgeek (Dec 8, 2010)

here is the link:
Fixed Link to Flux Recipe

Posted in this thread:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=242


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## lazersteve (Dec 8, 2010)

Does it work now?

Steve


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## oldgeek (Dec 8, 2010)

Yes it does! you are the man.

The entire thread is a good read. There is so much free information on this forum. You guys are the best!

Thanks
Scotty


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## 4metals (Dec 8, 2010)

Fluxing values out of furnace brick and old melting dishes is difficult because these materials are refractory in nature. It is difficult to liquefy a mixture of this material with any flux. Flourospar will liquefy a thick slag but I doubt its effectiveness on a refractory material mixed into the flux, for this I would use Kryolite, also a flouride but it can dissolve ceramics. It's not fast, it takes a long hot melt to liquefy this type of charge. 

A more effective way to recover your values is to crush the material to a -60 mesh powder in a ball mill and screen out the metallic oversize, which will be made up of your values. Since the values are clinging to the furnace parts and melting dishes as fine beads, they will not crush up and will be in the oversized material. This will not get all of the values, some will undoubtedly be in the fine powder, but a fire assay will tell you how much is in the powder, and if melting is required, the small mesh size of the crushed material will make and flouride based fluxing more effective.


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## Harold_V (Dec 9, 2010)

I'm afraid I have to agree with 4metals. The waste material I processed with the flux in question was high in silica, so it responded very well. My waste contained virtually no material that wouldn't dissolve in soda ash. Your circumstances are very different. 
What may yield results, however, is to process your material with a goodly amount of a collector, along with a generous fluid slag. Expect considerable degradation to the crucible, but with a prolonged soak at a high temperature and a thinned flux, it's possible the prills will accumulate in the collector you choose. Silver would be my choice. It might be worth a test run to determine if it would work, or not. 

In this case, you would not dissolve the refractory material, but the fluid slag should allow the prills to flow freely away from the solid bits. They are likely trapped in slag that will dissolve. 

Harold


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## oldgeek (Dec 9, 2010)

Thanks guys. I sincerely appreciate the knowledge that flows freely here. I have learned the hard way to gather all information you can about a process BEFORE you go forward, it will save you many headaches, time, and dollars. If i had only found this forum about two years ago, i would have turned a small profit in this hobby by now!

I think i will try to incorporate the suggestions from both of you when i get around to doing this.

Should i still use the following flux recipe, or is there a better flux mix for my application?

(3) parts waste material 
(1 ½) parts silica sand
(3 ½) parts soda ash
(1/2) part fluorspar
(2) parts borax

*(1/2) part "collector" of choice

I know i need a low viscosity flux, but i do not really know HOW to mix one. I have all of the ingredients listed above, so i would like to stick with them if possible.

Also, should the flux "parts" be weighed or measured out? I suspect i should weigh them out.


Thanks again,
Scotty


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## Anonymous (Dec 9, 2010)

I'd like to see a response to this mixture as well.This is close to the recipe I saw for ore,but I'd like to know what any smelting pro thinks about it for escrap.


oldgeek said:


> Also, should the flux "parts" be weighed or measured out?


Since everything is anhydrous(dry) it needs to be weighed.


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## Harold_V (Dec 10, 2010)

oldgeek said:


> Should i still use the following flux recipe, or is there a better flux mix for my application?
> 
> (3) parts waste material
> (1 ½) parts silica sand
> ...


Sure. Stick with them, and if you find it's not working exactly as you'd hope, start making alterations. Remember, none of this is carved in stone---and my circumstances were very different from yours. 



> Also, should the flux "parts" be weighed or measured out? I suspect i should weigh them out.


In my case, it was all done by volume. I chose a small container that represented a reasonable amount, then used it for everything. The very pleasant surprise I received was when I added water. I knew I'd have a terrible problem with blowing soda ash and borax away, along with some of my values. In my case, I melted directly in the furnace, with no crucible, so the entire charge was subject to the violence of the blower and ensuing flame. 

Back to the pleasant surprise----I added water, in my case it was about 600 ml, and stirred to mix things well. To my surprise, in short order, the mixture started setting. I discovered that I could mix everything, stir well, then pour to a form and allow the material to set hard. I had a number of plastic ice cream bucket lids handy, so I chose them as my form. The mixture was stiff enough to create a thick section in the center, so I'd pour until the edge of the lid was filled, then allow them to firm up. They could be removed after a couple hours, then I'd allow them to dry fully. Once dry, a smack in the center with a hammer reduced them to four or five small pie shaped sections that would be easily charged to my furnace. The good part was that the process eliminated dusting completely. The hard pieces would transform from solid to molten with perfect tranquility. 

I encourage you to do a few test lots, playing with ratios. No harm done if they don't turn out perfect, for you'll just send it to the furnace anyway.

The formula I used yielded exceptional results, but keep in mind, my material was laden with silver chloride (to act as a collector) and was primarily silica in nature. Much of my waste material was fiber glass (filters from my fume hood that had been incinerated). Silica is very easy to process. I added yet more silica in the way of (silica) sand to help reduce the attack on the furnace lining. In spite of using a 94% alumina, the interface between the top of the slag and the combustion chamber was rapidly eroded. The furnace required repair after three days of operation. That's the nature of using an aggressive flux. 

Fluorspar serves to thin your slag---you may wish to use more or less. Using less will reduce the amount of destruction, but soda ash alone serves to dissolve things, so it can't be avoided totally. 

I had my slag assayed to determine if I was achieving the hoped for results. While I don't recall the numbers now, the slag contained so little value that it was not accepted by a company that specialized in recovering small amounts of values from slag. It was their opinion that it should be discarded. That was all the evidence I needed to know that I was on the right track. 




> Thanks again,



Sure enough! I hope some of this will be useful to you. 

Harold


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## Anonymous (Dec 10, 2010)

Thanks harold.I am golng to try to make a few lids with that MgO,for my crucibles to stop the aggression monster from escaping.
Or another Idea I had was to take an old kiln lid that I have ,drill a ahole in the top large enough to "hold" the crucible like a tilt furnace,and heat it that way.Then I wouldn't have flux fumes inside the kiln.


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