Getting started refining jeweler bench sweeps

[Stonecutter1]

Greetings, just found this forum recently. I am preparing to try to process many years worth of sweeps. These have been collected from my bench pan and top of my bench. Alot of gold, silver and some platinum and Palladium as well. Would it be best to incinerate the material first either on an outdoor cooker on a large stainless pan or maybe using a burn out oven to burn off organics and other stuff. I have several hundred grams of material to process so I was thinking of starting small, maybe 200 grams to start. After incinerating and crushing or grinding in a mortar what is next ? Removing magnetics? Is it ever feasible to go right into Acid bath or Lye to process?

 

[etack]

Look for Harold's way on bench sweeps best step by step there is for sweeps

Eric

 

[4metals]

Bench sweeps are different than polishing sweeps so processing them in acid will give you the best results. They do have to be incinerated before you start with any chemistry.

Next you have to crush them which you can do in a mortar and pestle. Then a magnetic separation for removing all of your bits of saw blades and springs and anything magnetic.

Next I would screen the powder through a mesh screen about 40 mesh. This will separate the classic sweeps material from any oversize. The oversized material in the screen is karat gold or silver and Platinum or a combination of all 3. If this is enough material to process, as a few ounces, it is best to inquart this material and process as typically inquarted gold which you can look up in the library.

Then the powder can be processed as sweeps. If you think it contains a lot of silver it would be wise to leach it in nitric acid and distilled water to recover the silver before going for the gold. If you have worked on a lot of gold fill and suspect there can be an appreciable quantity of tin, nitric first will make a difficult to filter mess. If this is the case you need to treat in hydrochloric first.

I suggest you go to the library index from the link in my signature line and read up on both sweeps and inquarted gold.

Welcome to the forum.

 

[nickvc]

One point to remember is that many modern platinum casting alloys are magnetic so the removed magnetics need treating to remove the base metals.

 

[autumnwillow]

What I do for bench sweeps is incinerate, grind with mortar, remove magnetics, melt with soda ash/nitre/borax flux mix in a 1:1 weight ratio, assay then process in nitric then ar.

I have found that going directly for AR will result in losses due to the carbon from the incinerated materials. And you would also have to exclude large pieces since this will not be attacked by the acids.

Please please please, do an experiment yourself, process 200g using my method and 200g using other methods.

 

[Stonecutter1]

Thanks guys, for all the tips, I appreciate it. I plan to start in a couple weeks. Will continue to research, and get supplies. This is my first attempt at doing my own refining. Be in touch.

 

[FrugalRefiner]

Stonecutter, download the book in my signature line below. It was written for jewelers and others who want to refine their own scrap.

Dave

 

[4metals]

melt with soda ash/nitre/borax flux mix in a 1:1 weight ratio

This mixture can leave a lot of beads in the slag, especially if the jeweler used carborundum wheels on the bench, which many do. You need some fluorspar to thin the mix and drop the beads. If there is excessive carborundum you need to go the next step and use cryolite.

Unfortunately bench sweeps are a type of material that require different treatment depending on some different conditions.

 

[g_axelsson]

I have found that going directly for AR will result in losses due to the carbon from the incinerated materials. And you would also have to exclude large pieces since this will not be attacked by the acids.

If you have carbon left then you haven't completed the incineration. It should be done until there is no carbon left.

Göran

 

[Barren Realms 007]

I have found that going directly for AR will result in losses due to the carbon from the incinerated materials. And you would also have to exclude large pieces since this will not be attacked by the acids.

If you have carbon left then you haven't completed the incineration. It should be done until there is no carbon left.

Göran

Carborundum is different than carbon. :mrgreen:

 

[g_axelsson]

I have found that going directly for AR will result in losses due to the carbon from the incinerated materials. And you would also have to exclude large pieces since this will not be attacked by the acids.

If you have carbon left then you haven't completed the incineration. It should be done until there is no carbon left.

Göran

Carborundum is different than carbon. :mrgreen:

Yes it is... your point?

Göran

 

[Barren Realms 007]

I have found that going directly for AR will result in losses due to the carbon from the incinerated materials. And you would also have to exclude large pieces since this will not be attacked by the acids.

If you have carbon left then you haven't completed the incineration. It should be done until there is no carbon left.

Göran

Carborundum is different than carbon. :mrgreen:

Yes it is... your point?

Göran

Just making sure no one thinks they are the same thing. :mrgreen:

 

[nickvc]

If you do have carborundum dust in any quantity I'd advise not to try melting it, it takes a fair amount of time and skill to get it completely right.
Incinerate your sweeps and remove magnetics, bear in mind my comment about PGMs, then go directly with nitric which should remove the base metals and silver, if you have a lot of silver in the material the PGMs will follow the silver into solution at this point any palladium definateley will, I'd would advise filtering the powders with good rinses to remove as much of the nitric and any silver in the solution then back into your beaker and cover well with HCl and slowly add nitric, do not go too fast or get it too hot and the gold should go into solution leaving the PGMs, filter and rinse again and then back into the beaker, again cover well with HCl and put onto heat then add nitric slowly to recover any PGMs.
This is not a perfect method as there will be some crossover of values most likely with the silver and PGMs and the PGMs and gold, bear in mind very very well that all PGM salts which is what they become when dissolved are highly toxic so use gloves and decent extraction.

 

[Stonecutter1]

Next question, any advice on what methods to use for incinerating, my plan is to do it outside using my camping stove. Probably with large stainless steel kettle.

 

[4metals]

That will work, a large cast iron skillet works too, just heat it until it glows. Igniting the surface with a propane torch while stirring it with a long metal rod that will not ignite to keep it burning. When it goes out try and re-ignite it with the torch until it glows a red ember but doesn't produce a lasting flame.

 

[Stonecutter1]

Next question, I plan to use a couple of sieves to screen out my sweeps before incinerating. There will be a fair amount of tiny pieces of metal scrap and stuff that doesn't go thru the screen. Can that material go right to nitric or AR to process? Another thing, I have worked with alot of nickel- iron meteorite in some of my designs, I have tried to catch most of my filings by covering my work area when working with this material but I know there a fair amount of filings from this in my sweeps as well. Looking for best advice for removing magnetic. Magnet or let acid remove it or ...?

 

[autumnwillow]

Incinerate before you sieve, follow 4metals advice. Or follow mine, you won't have to seperate the large pieces but most likely you will have to inquart.

 

[Stonecutter1]

Been so busy with other things, finally getting back to my refining project. I have incinerated a fair amount of material. I am going to go through it with a magnet today and then grind it all with a mortar and pestle and take it through a fine sieve. How would I know if there is carbon in it ( that was mentioned earlier) and would that cause a problem. My hope is that in the next week I will be ready to go to a nitric acid bath.

 

[4metals]

Heat a sample of the ash until it glows red with a torch, if it does not ignite and burn you have effectively removed all of the carbon with your initial incineration.

 

[Stonecutter1]

Thank you for that tip. I incinerated pretty thoroughly I think and removed all magnetics them ground it all quite fine and took it through I fine sieve so I think my first batch is ready for acid bath. One question I have a small bag of course material and pieces of different karatage and metals left over. Would it be best to process those separate in nitric? Not sure what all is in there.