# Cupellation - Now this is fun! Help?



## NoIdea (Sep 24, 2011)

Evening All – Cupellation? I have read what Hoke has to offer, spent hours reading all the forum posts I could find on this topic, assume stuff by the way, performed a real cool experiment and now it’s time to ask a few question, if I may. Bit of a description first.

I am having loads of fun, and wish for it to remain fun, in saying that you must keep in mind that I am using rudimentary/crude equipment, charcoal, coal, homemade incinerator/furnace/burning thingy, stainless steel bowls, lead from nail-heads and wheel weights, a spoon, safety wear, and a nice fresh breeze.  

Ok, my starting material was pyrolized low and high grade boards, of which most of the components were removed, leaving some chips, surface mounted items, and fingers intact.

After pyrolysis, the material was ground, sieved (the larger bits, greater than 0.5mm are metal beads/ceramics/glass, saved for later), incinerated, boiled in caustic soda x2, washed with hot water x2, and again incinerated producing a fine powder.

The lead consisted of wheel balance weights and lead head nails; I had a small tin can filled with slag left over from melting lead for sale, with all of the iron removed from the lead.

I placed a quantity (?) of the material into a stainless steel bowl, this was placed on the incinerator and brought up to a dull red, at which point I added the lead/lead slag, which weighed (?), waited for it to melt and smoke, added old activated charcoal (from the homebrew Gin days), at this point I started to stir and swirl the mix. 

The mixing and swirling caused puffs of brown dust (which stayed inside the bowl), I covered the bowl for a couple of minutes, removed lid, stirred and swirled, periodically adding more carbon when it stared to smoke, repeating this process until the melt started to stiffen, requiring more heat to regain a melt. At this point I stopped, took the bowl off the heat, gave it a few giggles, like you were gently panning for gold fines, and set the bowl on its edge to cool. The nugget so produced looked similar to the nugget to the right in the picture, which weighted 187g. I should note that at no stage after the lead had melted into the sample mix, was the lead visible but I could feel it moving along the bottom.


The nugget produced was reheated till completely melted, and then I skimmed off the oxide slag, which was a rainbow of colours, I stopped before the nugget got too small and cast, resulting in the nugget to the left of the picture.

The slag produced from the skimming was put back into the material left over from the formation of the first nugget, ground in my grinder along with more charcoal, producing the nugget to the right of the picture.

Ahh, now its question time:

1. How do you know when all the lead has been removed? No more oxide produced and is this temperature dependent?
2. Any idea as to the pretty colours produced during the skimming?
3. I read a post where an iron ladle was contaminated with gold, silver, and lead was advised as a mean to pull them out of the iron, at what stage will the silver content/concentration within the lead, prevent this pulling power?
4. Remembering my financial situation, I can not afford the more suitable equipment, so please advice, and comment away, please.


Thanks

Deano


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## butcher (Sep 24, 2011)

I would take a portion and oxidize it in bone ash cupel weighing before and after should tell you how much lead you lost to bone ash, since your such a fire bug you could make your own pyrolyzed(bones) bone ash cupels, but believe me it stinks, almost as bad as incinerating dental gold.

Rainbow colors could be oxidized lead and other metals, there may also be values in the skimmed of dross, that did not amalgam with lead.

not sure but if a lot of lead adding an oxidizer like NaNO3 may help in oxidizing the lead, perhaps making litharge, which bone ash could soak up easier.

garden center sell bone meal if you do not have a pile of animal bones (I have a large pile, I know the hill the highway dept dumps road kill, and coyotes drag around can collect a truck full in just few hours).

Why are you using lead for this it seems to complicate matters in my mind.

bone ash cupels are fairly cheap, but you said low budget project.


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## NoIdea (Sep 24, 2011)

Thanks Butcher - Yep gotta love the flame :mrgreen: 

I was hoping to build up the PM's in the lead which is skimmed, reusing the slag again and again. The aim is to produce a nugget that can be used in a silver cell.

I know lead can be a problem in the silver cell so performing cupellation with bone ash at the end may be an option. 

Im more concerned with draw-backs of this process, seems way too easy for processing e-waste.

Cheers

Deano


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## qst42know (Sep 25, 2011)

> 1. How do you know when all the lead has been removed? No more oxide produced and is this temperature dependent?
> 2. Any idea as to the pretty colours produced during the skimming?
> 3. I read a post where an iron ladle was contaminated with gold, silver, and lead was advised as a mean to pull them out of the iron, at what stage will the silver content/concentration within the lead, prevent this pulling power?
> 4. Remembering my financial situation, I can not afford the more suitable equipment, so please advice, and comment away, please.



1.The production of oxides will be limited by the concentration of PM's. You likely achieved an alloy that resists oxidation. That doesn't mean all the lead has been removed, you may need much higher temperatures than your stainless vessel can tolerate to remove the last of the lead. In a cupel at the right temperature and oxygen supply the last of the lead sweats off the bead as bright red very fluid droplets that are absorbed by the cupel.
2.The colors indicate metals other than lead.
3.Lead and (and I believe) silver won't wet bond to iron, increasing the content of either should free the button from the iron ladle.
4. Servicable cupels can be made from straight portland cement, or roasted bone meal from the garden center with a fairly simple mold and a lever operated press.

[spelling edit]


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## Geo (Sep 25, 2011)

can you purchase cupelling dishes or do you have to make your own? is it more economical to make your own as apposed to time saved in buying them?


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## qst42know (Sep 25, 2011)

Geo said:


> can you purchase cupelling dishes or do you have to make your own? is it more economical to make your own as apposed to time saved in buying them?



You can buy them and they don't cost much if you can find them nearby to save on shipping, but the last time I bought an 80# bag of Portland cement I think I paid about $8, enough for hundreds of cupels.


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## NoIdea (Sep 25, 2011)

Hi Boys and Girls – here is my latest nugget, I would love some feed back, when cast there was no coloured oxide, just what you see.




How does the colour look?

I need to make a cupel to finish it off.

Deano


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## qst42know (Sep 25, 2011)

It's plenty white, perhaps tin white?

Was there much solder in the mix?

Have you acid tested this metal?


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## butcher (Sep 25, 2011)

looks clean, how hard is it, how does it react to things like iron nails copper, finger nails, will a pocket knife cut it easily? what is its density, how easy did it melt, it is white was there much silver in the scrap? I do not see a copper look to it. is the melt of it uniform?, maybe cupel a sample of it and part the bead to get more of an idea?


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## Harold_V (Sep 26, 2011)

My opinion? Very white---silver type white. Lead has a gray cast----and tin has a hint of yellow. That the button lacks oxides speak volumes about its potential purity. 

I did very little in the way of cupelling, but I did do a little, all by torch, and without a cupel. I'd do it in a melting dish, pouring off the created litharge. What I learned was that towards the end, the button no longer supports combustion, so you must use fuel. Once heated, only oxygen was required to support conversion. The smoke was something to behold, by the way. I did all mine in a fume hood, and would likely have died from lead poisoning had I not. I do not recommend the process, in spite of the fact that it does work. 

In the end, the button will superheat (from heat from the torch), but no fumes well be liberated. Time to call it good. Of course, this would have been best done in a cupel, so traces of lead would have been absorbed. I had none at my disposal at the time. 

Harold


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## Geo (Sep 26, 2011)

can you use that in a silver cell as is or do you recast in an anode?


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## NoIdea (Sep 26, 2011)

Thanks for the replies, I saw the earlier replies and hurriedly raced outside and did some more skimming. 



qst42know said:


> It's plenty white, perhaps tin white?
> 
> Was there much solder in the mix?
> 
> Have you acid tested this metal?



This particular nugget, came from a processed powder which had AR run through it, origin, unknown, though I do believe it was high-ish in silver plus some ashed anode mud. No copper, made sure of that. Tin should be as the oxide.



butcher said:


> looks clean, how hard is it, how does it react to things like iron nails copper, finger nails, will a pocket knife cut it easily? what is its density, how easy did it melt, it is white was there much silver in the scrap? I do not see a copper look to it. is the melt of it uniform?, maybe cupel a sample of it and part the bead to get more of an idea?



Knife – slices with effort, not as easy as lead
Fingernail – not that easily, but some did come off, not enough to collect under the nail.
Melting – became harder the more I skimmed, way higher than lead, melt was uniform.
Density – balance does not go higher than 149g, though the newest nugget feels way heavier than it looks.
Dilute nitric – pretty cool, produced or allowed a yellow tint within the nugget to show itself, I then wiped it with a cloth which went grey. Yellow tint slowly vanished; it can still be seen in the right light. No greens or blues
HCl – went grey.

It has a nice metallic ring to it. Has other PM's in it as well

I have definitely learnt a few things today; heat plays a big role, though I have no means of measuring it, just by eye.

I accidently did an experiment by not adding enough lead, not a good idea, way too much smoke.

Cupellation will come after I have processed a little bit more, though I would also like to know the limitation of the silver cell in terms of contamination.

Thanks heaps for the help.

Deano


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## nickvc (Sep 26, 2011)

Deano all cells work best with the least hassle with high purity materials, at least 95%+, but knowing you I'm sure you will find a method to cheat this, but the silver produced will be of questionable purity and fouling of the electrolyte will be fairly quick. If you are short of money to invest in quantities of silver I'd run small cells to get started and when more fine silver becomes available grow bigger.
Keep up the research and posting it's always enlightening.


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## NoIdea (Sep 26, 2011)

nickvc said:


> Deano all cells work best with the least hassle with high purity materials, at least 95%+, but knowing you I'm sure you will find a method to cheat this, but the silver produced will be of questionable purity and fouling of the electrolyte will be fairly quick.
> 
> Keep up the research and posting it's always enlightening.



Thanks nickvc, I am having fun and learning lots at the moment with the hope of a reward at the end. May ask later at sometime to see if anyone would like to refine the final nugget, should have a bit of other values other than silver in it.

In terms of silver and silver cells, well, that’s been taken care of by Lazersteve and members from this forum, that’s one Wheel ill leave alone.

Anyone cupeled using Plaster Of Paris, or used it as a binder with bone ash? Lots of rivers around here, lots of animal bones, sheep mainly, might payee the kids to go grab a bunch for me. :lol: 

Again, Thanks.

Deano


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## seawolf (Sep 26, 2011)

I found this posting on Google it has a section on cuples. It was written befor we were able to pick up the phone and call a supplier for items we need.

1.	De Re Metallica-Assaying Ore | Testing page 266
small mortar, and then mould the cupels. In the works in which silver is separated from copper, they make cupels from two parts of the ashes of ...
www.farlang.com/gemstones/agricola-metallica/page_266 - Cached - Similar

Hope this might help, Mark


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## Dr. Poe (Oct 26, 2011)

I suggest that you buy your cuppels. They don't cost much if you buy a case at a time. Then keep them in the case box completely submerged in baby powder (Talc, not corn starch). This keeps them from cracking when you put them in your oxidizing furnace. The talc also helps seal the pores so that only liquid molten litharge is absorbed into the cuppel.
Use talc (which is ground soapstone) to fill the cracks in your furnace after each smelt. Unless your furnace is high temperature carbon arc or electric induction, you will never melt the talc. Dr. Poe
P.S. Bismuth can be substituted for lead, works great and is less toxic.


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## 4metals (Oct 26, 2011)

I was told that lead used for balancing tires is high in selenium.


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## NoIdea (Oct 26, 2011)

4metals said:


> I was told that lead used for balancing tires is high in selenium.


 :shock: 

Gee thanks 4metals, just throw another stick in my brew why don't you :lol: 

Took my family out to the river to look for bones, about an hour later we found a cows hip bone. We all grabbed some firewood, headed home to ash the hip bone in my small fire pit. Sorry, no pictures.

When I make a little cupel for testing i will take some pictures.

Thanks for the replys.

Deano


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## butcher (Oct 26, 2011)

In the back of my mind seems like portland cement will also work like a cupel, you may try to find if its true, if so maybe you could mix your bone ash with it to make it go further.


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## Harold_V (Oct 28, 2011)

4metals said:


> I was told that lead used for balancing tires is high in selenium.


Antimony, not selenium. 

Harold


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## 4metals (Oct 28, 2011)

> Antimony, not selenium.



I stand corrected. 

Do you know how much antimony?


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## qst42know (Oct 28, 2011)

Around 5% I would expect, at least that fits the definition of hard lead.

But Rotometals carries it up to 30% antimony, more for blending custom bullet alloys.

http://www.rotometals.com/Antimony-s/1.htm

The link from Rotometals has a more complex ratio for clip on wheel weights.

http://www.lasc.us/SuperHard.htm



> 2% Sb and 0.5% Sn plus a trace of arsenic (As).


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