Refining a huge chunk of lead and gold

[Hbartamian]

So this is going to sound ridiculous but here goes. I had about 1000 grams of lead I purchased (a bunch of lead weights from a fishing shop) and 60 grams of scrap gold. I put it all into an iron skillet and laid a bed of Portland cement thinking I could cuppel it’s all in one go. After about an hour of blowtorching and melting it all together, ended up with slag and a melted metal that looks like a meteorite with particles spread out. I’m just starting out with refining and by this time, I think I made a mistake by mixing about 1000 grams of lead into about 60 grams of scrap gold.

I immediately starting reading some books on proper scarification and Cuppel long but they all talk about smaller quantities of lead and gold, meaning then charge to do this right would be huge. What size crucible would I need? Do I just melt it all up inTo one solid and chop it down. Could I still successfully Cuppel this in one go? what would you recommend to be the next course of action? What equipment and flux would I need to get rid of any ferrous metals for this compound I ended up making?

 

[goldshark]

I am assuming you melted the Iron skillet, at least partially. Scrape all you can free, wash the Portland off well, place in a crucible, place crucible in a furnace which will attain a heat of 2000 F. When Lead and Gold alloy are liquid, pour into a cone mold, decanting the Pb/Au alloy, leaving what still solid Iron is left in the crucible. Chip off any remaining slag. 1000 grams is a lot to cupel all at once. I would think you could also pour into other molds around 100 grams in size. My bigger store bought cupels, only absorb 165 grams of Lead ,maximum, and they are the biggest I could find. So dividing into 100 gram lots would be much easier. If you go the compressed Portland hack, you will need a cupel roughly 2 1/2"x 3" high, with enough depression to hold 100 Grams when melted flat, with perimeter space to allow for PbO to start absorbing into the cupel. Mind you, the entire cupel needs to attain 1850 F to work properly. Surface heating with a propane torch does not work. An electric cupeling furnace is probably the best for a beginner. Remember to crack the door very slightly to allow for a little Oxygen. That size slug may take 45 minutes to an hour to cupel at a constant 1850F heat, cupel pre heated to temperature of 1850. Make sure slug is completely dry, before placing in hot cupel. Remember all safety protocols, especially for the Lead fumes. Hacks shown on Youtube, do not work very well. For professional results, use professional equipment and supplies. I would find a professional assayer, and see if they will do what you want. The proper equipment and supplies will cost you 1000's. Invest in it if you continue to find interest in this. Otherwise, cut your losses while you are even. An assayer will probably charge you a couple hundred dollars for his service, just a heads up.

 

[Yggdrasil]

So this is going to sound ridiculous but here goes. I had about 1000 grams of lead I purchased (a bunch of lead weights from a fishing shop) and 60 grams of scrap gold. I put it all into an iron skillet and laid a bed of Portland cement thinking I could cuppel it’s all in one go. After about an hour of blowtorching and melting it all together, ended up with slag and a melted metal that looks like a meteorite with particles spread out. I’m just starting out with refining and by this time, I think I made a mistake by mixing about 1000 grams of lead into about 60 grams of scrap gold.

I immediately starting reading some books on proper scarification and Cuppel long but they all talk about smaller quantities of lead and gold, meaning then charge to do this right would be huge. What size crucible would I need? Do I just melt it all up inTo one solid and chop it down. Could I still successfully Cuppel this in one go? what would you recommend to be the next course of action? What equipment and flux would I need to get rid of any ferrous metals for this compound I ended up making?

Welcome to us.
Listen to Goldshark his advice is good in your situation.
Why did you melt your scrap Gold with lead? It would have been much cheaper and easier to refine it directly by inquarting or direct dissolving.

 

[orvi]

Yup. If by scrap gold is meant scrap jewellery, there is absolutely no benefit of cupelling it with lead. Maybe some copper from the karat will be removed, but overall silver and gold remain together.

Some photos will certainly help us to determine what happened. Did the molten lead/gold touched the iron ? Or drained to the bottom of the pan through cement ?

If you still have metallic chunk, it will be wise to re-melt it in some crucible and weigh it. That way you will know how much lead you have in it and if it is not overwhelming excess, maybe you can dissolve the metal in nitric acid, removing lead and silver, leaving gold powder. Waste treatment would be relatively easy, as you can cement silver with copper and get rid of the lead by pouring in sulfuric acid or any soluble sulfate solution (pH - pool chemical is NaHSO4 for example).

But I never dissolved "lead" inquarted metal in nitric acid, so I will wait for somebody more experienced in this procedure to give his opinion. Lead can sometimes act strange in acids... Cupelling it to the end is also the option, but assuming this first run did not gone well...

 

[Hbartamian]

I am assuming you melted the Iron skillet, at least partially. Scrape all you can free, wash the Portland off well, place in a crucible, place crucible in a furnace which will attain a heat of 2000 F. When Lead and Gold alloy are liquid, pour into a cone mold, decanting the Pb/Au alloy, leaving what still solid Iron is left in the crucible. Chip off any remaining slag. 1000 grams is a lot to cupel all at once. I would think you could also pour into other molds around 100 grams in size. My bigger store bought cupels, only absorb 165 grams of Lead ,maximum, and they are the biggest I could find. So dividing into 100 gram lots would be much easier. If you go the compressed Portland hack, you will need a cupel roughly 2 1/2"x 3" high, with enough depression to hold 100 Grams when melted flat, with perimeter space to allow for PbO to start absorbing into the cupel. Mind you, the entire cupel needs to attain 1850 F to work properly. Surface heating with a propane torch does not work. An electric cupeling furnace is probably the best for a beginner. Remember to crack the door very slightly to allow for a little Oxygen. That size slug may take 45 minutes to an hour to cupel at a constant 1850F heat, cupel pre heated to temperature of 1850. Make sure slug is completely dry, before placing in hot cupel. Remember all safety protocols, especially for the Lead fumes. Hacks shown on Youtube, do not work very well. For professional results, use professional equipment and supplies. I would find a professional assayer, and see if they will do what you want. The proper equipment and supplies will cost you 1000's. Invest in it if you continue to find interest in this. Otherwise, cut your losses while you are even. An assayer will probably charge you a couple hundred dollars for his service, just a heads up.

Thanks goldshark, I luckily didn’t get the iron mixed with the lead and gold, there was enough of cement bed to keep the molten metal separate. I think I will go the remelt option and check out the as I do enjoy this regardless of the mistake. does it warrant adding any sort of flux to the melt before pouring bars?

 

[Hbartamian]

Here’s what it currently looks like

Yup. If by scrap gold is meant scrap jewellery, there is absolutely no benefit of cupelling it with lead. Maybe some copper from the karat will be removed, but overall silver and gold remain together.

Some photos will certainly help us to determine what happened. Did the molten lead/gold touched the iron ? Or drained to the bottom of the pan through cement ?

If you still have metallic chunk, it will be wise to re-melt it in some crucible and weigh it. That way you will know how much lead you have in it and if it is not overwhelming excess, maybe you can dissolve the metal in nitric acid, removing lead and silver, leaving gold powder. Waste treatment would be relatively easy, as you can cement silver with copper and get rid of the lead by pouring in sulfuric acid or any soluble sulfate solution (pH - pool chemical is NaHSO4 for example).

But I never dissolved "lead" inquarted metal in nitric acid, so I will wait for somebody more experienced in this procedure to give his opinion. Lead can sometimes act strange in acids... Cupelling it to the end is also the option, but assuming this first run did not gone well...

here’s what it currently looks like

 

[Hbartamian]

Welcome to us.
Listen to Goldshark his advice is good in your situation.
Why did you melt your scrap Gold with lead? It would have been much cheaper and easier to refine it directly by inquarting or direct dissolving.

Noob mistake reading about cupelation. The gold definitely had some impurities so I was trying to get rid of them.

 

[Hbartamian]

would this be a good start Electric Furnace

 

[Hbartamian]

Another question i had, was if I have delft clay or sand, could I use it to make small molds to have 100 gram pieces? Has any one ever used the clay or sand to pour a scorcified melt Into a pyramid?

 

[goldshark]

would this be a good start Electric Furnace

This is a good furnace for heating and pouring metals only. However, a front door with a flat bottom, heating coils on the side, is a much better choice for cupeling. Check out the small furnace Jason from Mount Baker Mining and Metals uses for cupeling. That model would be more suitable for your needs. Also notice how he keeps the door slightly cracked. Sorry, don't have a link for that model.

 

[goldshark]

Thanks goldshark, I luckily didn’t get the iron mixed with the lead and gold, there was enough of cement bed to keep the molten metal separate. I think I will go the remelt option and check out the as I do enjoy this regardless of the mistake. does it warrant adding any sort of flux to the melt before pouring bars?

I can't tell what the crumbly stuff is on the upper right of metals is. If you have a large enough crucible to re melt the mass, enough Borax to cover the melt would aid in collecting the non metallic portion. 1/8" layer is plenty to collect it all. If you don't have access to Borax, careful skimming with a spoon may clean most of it up. This is where a cone mold really helps. Lets the metal sink, slag float. Hammer/ wire brush all slag from metal upon cooling. Steel or cast iron molds are preferred for construction of cone molds. Graphite is preferred for ingot molds. Most other ceramics will crack due to thermal shock. There are some specialty ceramics out there which can be used, but for simplicity, use the recommended in the industry.

 

[Martijn]

So this is going to sound ridiculous but here goes. I had about 1000 grams of lead I purchased (a bunch of lead weights from a fishing shop) and 60 grams of scrap gold. I put it all into an iron skillet and laid a bed of Portland cement thinking I could cuppel it’s all in one go. After about an hour of blowtorching and melting it all together, ended up with slag and a melted metal that looks like a meteorite with particles spread out. I’m just starting out with refining and by this time, I think I made a mistake by mixing about 1000 grams of lead into about 60 grams of scrap gold.

I immediately starting reading some books on proper scarification and Cuppel long but they all talk about smaller quantities of lead and gold, meaning then charge to do this right would be huge. What size crucible would I need? Do I just melt it all up inTo one solid and chop it down. Could I still successfully Cuppel this in one go? what would you recommend to be the next course of action? What equipment and flux would I need to get rid of any ferrous metals for this compound I ended up making?

I think this may be the answer to your problem: There is a video where the precious metals are transferred to zinc in a melt, skimmed off. Then smelted again to oxidize the zinc out.

 

[Hbartamian]

I can't tell what the crumbly stuff is on the upper right of metals is. If you have a large enough crucible to re melt the mass, enough Borax to cover the melt would aid in collecting the non metallic portion. 1/8" layer is plenty to collect it all. If you don't have access to Borax, careful skimming with a spoon may clean most of it up. This is where a cone mold really helps. Lets the metal sink, slag float. Hammer/ wire brush all slag from metal upon cooling. Steel or cast iron molds are preferred for construction of cone molds. Graphite is preferred for ingot molds. Most other ceramics will crack due to thermal shock. There are some specialty ceramics out there which can be used, but for simplicity, use the recommended in the industry.

Crumbly stuff is just Portland cement bits. Thanks for the advice.

 

[Hbartamian]

I think this may be the answer to your problem: There is a video where the precious metals are transferred to zinc in a melt, skimmed off. Then smelted again to oxidize the zinc out.

Thanks, found out it’s called the Parkes process

 

[goldshark]

I was going to mention this also. Be very careful when evaporating the Zinc. a little goes a long way towards destroying your health. Both have inherent risks from fumes. The advantage of the Parkes process over cupeling, is you will lose all the Lead to the cupel, generating a lot of toxic waste to deal with, while the Parkes process will lose a comparatively small amount of Zinc to fumes. I cannot stress enough about the toxicity of Zinc fumes.

 

[Martijn]

I was going to mention this also. Be very careful when evaporating the Zinc. a little goes a long way towards destroying your health. Both have inherent risks from fumes. The advantage of the Parkes process over cupeling, is you will lose all the Lead to the cupel, generating a lot of toxic waste to deal with, while the Parkes process will lose a comparatively small amount of Zinc to fumes. I cannot stress enough about the toxicity of Zinc fumes.

Jason oxidizes the zinc with soda and potassium nitrate and absorbs the oxides in the slag. I'm sure there are zinc fumes to watch out for, but most goes in the slag as i understand it.

 

[Hbartamian]

I was going to mention this also. Be very careful when evaporating the Zinc. a little goes a long way towards destroying your health. Both have inherent risks from fumes. The advantage of the Parkes process over cupeling, is you will lose all the Lead to the cupel, generating a lot of toxic waste to deal with, while the Parkes process will lose a comparatively small amount of Zinc to fumes. I cannot stress enough about the toxicity of Zinc fumes.

I was going to use this through out the whole process Mask

 

[Hbartamian]

Based on what I’ve gathered, the process I‘ve so far worked out is the following:

1. For 1000 grams of gold and lead mix, Remelt Pieces back together with a charge of 400 grams of soda 100 grams of silica 15 grams of borax
2. let melt for an hour
3. pour into cone mold, remove slag
4. remelt with 50 grams of zinc so both are remelted together, stir up, keep melting for about 30 minutes
5. start cool down, keep lead liquified while zinc crustifies
6. scoop zinc
7. assuming mix of zinc and gold is 100 grams (for simplicity) melt together and oxidize with a charge of 100 grams soda 100 grams borax 50 grams of potassium nitrat.
8. pour into cone mold, separate button
9. cuppell
10. pour refined gold into mold
11. Dont die of fume poisoning

Does this make sense? I think my flux amounts are too high.

 

[Hbartamian]

The alternative being melt down the piece to about 10x 100 gram buttons and Cuppel these?

 

[Hbartamian]

This is a good furnace for heating and pouring metals only. However, a front door with a flat bottom, heating coils on the side, is a much better choice for cupeling. Check out the small furnace Jason from Mount Baker Mining and Metals uses for cupeling. That model would be more suitable for your needs. Also notice how he keeps the door slightly cracked. Sorry, don't have a link for that model.

that looks good for Cuppeling, for a backyard smelter would this also work Smelter