Jewelers filings and clippings

I started on this today using Harold's PDF as a guide

I found diamonds and other stones and pulled them prior to incinerating.

I did not do this screening because I don't have any screens yet.

I did the magnetic treatment by putting a magnet into a thick plastic bag, there was very little magnetic material to remove.

I incinerated using the pyroceramic Corning ware dish because I could not find a stainless steel pan at the thrift store as of yet.

The incineration went well and everything was heated to redness with a low flame from propane torch while the casserole was on high heat.

I did a stannous test on the nitric and there's some gold and Pt in solution - I goofed early on and added HCl instead of nitric!

Had to dry everything out and re-incinerate, but there was probably some residual HCl that caused some gold and Pt to go into solution.

There is a little Pt filings in this batch.

Back to the shop, I'll put some photos up later.

The next step is to inquart and I am at a loss here on how much silver to add - educated guess. Any input would be greatly appreciated.

kadriver

I has extracted all the silver and palladium using nitric acid.

A stannous test shows some type of PGM in the green liquid.

Probably palladium rather than platinum.

Since I did not have screens to sieve the filings, I ended up with all the filings and larger pieces in one group in the casserole.

I was trying to figure a way to calculate how much silver to use to inquart.

I looked in RPMW by Hoke and found the section on buttons and alloys.

I decided to throw everything in a melt dish and make a button.

It weighed 32.6 grams.

The button in hand, I used karat gold needles, touch stone, and acid to test the karat of the button.

It was between 14k and 18k, so I interpolated the button was 16k gold.

I used these numbers to calculate for inquarting - the material is being treated in nitric acid as I write this.

More pictures to follow.

With screens you can process filings directly, as heated nitric will remove a great deal of the alloy before being stopped by the presence of gold. What remains will readily dissolve in AR, so it saves the melting process, as well as having to use silver, which you may or may not have in abundance. Pieces that do not pass the screen can then be inquarted.

The negative aspect of directly dissolving the filings is that the quality of the resulting gold is questionable, due in part to the larger amount of base metal that is carried through the process. For me, that wasn't an issue, as I either used such gold for making buttons used in evaporation, or it was simply refined a second time, as was my normal practice.

If you process filings directly, without melting, you will be best advised to use a slight excess of nitric when you dissolve the gold. That way you'll recover all of the gold. Filings tend to be loaded with small particles of abrasive (from Cratex wheels), making it difficult to discern values from the "dirt".

Harold

Harold, I didn't realize that skipping the sieve was going to be a problem. If I had done it as per your PDF I would have been OK. I would have had the large pieces to inquart, then I could process the filing separately - if I had screened the material first.

This was a new learning experience and I gained much from it.

Melting everything into a button then inquarting worked well.

I finished this up just now and will have it ready to present to my friend this morning as promised.

Melting the filings and clippings into a button was kind of tricky, I had to stir with a graphite rod to get all the metal into one spot in the dish.

I used borax because I had placed all the material into a filter paper and then everything went straight into the melt dish.

Covering the wet filter with borax before applying the torch keeps all the paper in the dish as it burns away instead of flying up into the air. The borax acts as glue to keep the bits of ash from the filter paper in the dish.

I got it so hot that part of the dish melted, I think. The button was buried in what look like magma from a volcano.

I tilted the dish sideways and the button came thru the magma, hardened a bit, then I plucked it from the dish with long metal tweezers before the magma substance hardened and imprisoned the button.

I broke the dish apart after it cooled to make sure there were no small balls of metal that got left behind.

Here is the pure gold from the filings - this was a little more nerve-racking because I was totally unfamiliar with this process.

Next tine I'll have screens and do it to the "T" following Harold's outline.

kadriver

Assuming you can successfully melt the filings for inquarting, the end result will be better. I've never had a problem with that idea, but it comes at a somewhat higher price. The problem is, unless you flux VERY well, you experience what you witnessed. I learned, early on, that melting filings wasn't the smartest way to process, assuming you're concerned about destroying melting dishes and creating the lava like slag you created.

And now the real problem. If you flux adequately, you're going to be correspondingly hard on the melting vessel. That may or may not be a problem for you.

If you insist on melting, you should pour to a cone mold. That will ensure that all of the values are collected in one piece, and make it very easy to separate the values from the flux (slag). Again, in order for this to work adequately, you must flux adequately. You have to add enough borax for the flux to be fluid. You may even discover that there's a small benefit in adding soda ash, but that accelerates the destruction of your melting vessel.

All in all, I found processing filings to go much better by processing without melting, and almost NEVER melted first. There were exceptions, although I'm at a loss to describe when, or why. It's been too long to recall. Bottom line---I was happier to achieve a somewhat lower quality by direct dissolving than I was to achieve a higher quality by melting, keeping in mind that in either case, I'd re-refine the gold. In your case, where you may not be refining a second time, you may find that melting is in your best interest. All depends on your personal agenda, and the quality you hope to achieve. You did good, and, remember, this isn't about being right or wrong--just about what works best for you and your circumstances.

Harold

Harold,

I was short on time with this because I needed to get my friend his gold quickly as promised. My promptness paid off and I secured my friend as a customer and I now have more work than I can handle because he had a friend who has much material to be processed also.

This happened at a perfect time as I was considering scaling down my shop and renting out the house for income. Refining wasn't paying the bills like it used to for me because the flow of scrap gold and silver has slowed way down.

But, just like you said, I am having a hard time because I now have more work than I can keep up with. But this is a good problem to have, just like you said!

I also have to get on the stick with getting the PGMs because there was a considerable amount of Pd and a little Pt in both the filings and the polishing sweeps.

I have another bag of filings that is about 3 times as much as this first sample and I'll be getting that just as some as I finish the kilo of high grade coarse polishing sweeps.

I had about a heaping table spoon and a half, or so, of straight borax in the melt dish when I made the button because I had the filings in a wet filter paper then I put everything, filter paper and filings, in the melt dish to make the button.

I now have a regular kitchen wire strainer I got from Walmart to use as a coarse screen. I also have some very fine mesh copper screen that can be used as the second "fine" screen as per your PDF.

I also got a nice 14 inch Salad Master, thick stainless steel frying pan for incineration.

I bought a gross of melt dishes a while back and I have learned to reuse them instead of getting a new dish out every time I do a melt.

I must get a cone mold, been putting it off because they are expensive - about $80 on eBay.

kadriver

At the least, you should have a small cone mold (used by assayers). I had three different sizes, two of which were used fairly regularly, with the third size, the largest ones, used only when I operated my tilting reverberatory furnace.

I have long maintained that until one can capture some of the jewelry market, there will be an ongoing struggle to make a small refining operation work. It provides not only a source of gold and other valuables to refine, but also a ready market for selling fine gold at spot price. Once jewelers understand your quality is acceptable, and that you are reliable and can turn gold quickly, they won't leave you alone. The fast turn allows them to inventory less precious metal, which many find desirable.

In regards to traces of platinum and palladium in solution, I chose to recover them in my stock pot, in which I did NOT use copper. Do remember, neither of them will precipitate well from dilute solutions, and they are a serious drain on time if you play with each small batch, typically with little success, if any.

I chose to use scrap steel, secure in the knowledge that in order to affect a recovery by furnace, I would need a collector. it was for that reason that I was not concerned about using tap water for the initial digest of inquarted materials, as the traces of silver chloride ended up in my waste materials, which also served as feed for the tilting reverberatory furnace, enhancing the collecting ability of the contained metals. In my case (a repeat of previous posts), it became my saving plan, for I stored my incinerated wastes until the very end of my refining career, at which time it was processed. My hunch in using scrap steel in my stock pot appeared to have been on target, as I achieved an exceptional recovery. It most likely would not be the best choice if one recovered the traces chemically.

Well done, kadriver!

Harold

edit:
Note that I used a small fry pan for incinerating filings. The size used by boy scouts proved to be ideal, and they tend to be available at second hand stores. I used the larger size for polishing wastes and floor sweeps.

Kevin in honesty I would have sieved, incinerated and processed in nitric to remove as much silver and Pd and then go straight to AR with heat. Most thin and higher karat material will dissolve easily, any large pieces take a little time but normally they do dissolve. As Harold pointed out the resulting gold powder will need refining again but it's much less hassle than inquarting.
If you get big pieces of karat material and lots of it then inquarting is the way to go especially if it's low karat where silver content can be high.

Harold and Nick,

Thanks for the tips.

Did you keep all the silver and PGMs recovered, or give credit (or the metal) back to the customer?

There was about an ounce of silver in the filings and maybe 1/10 gram (estimated) of PGMs left over after the gold was recovered.

I told the customer and he said he wasn't worried about them.

What did you folks do with these values?

The stock pot "retirement plan" is a good idea. Just keep adding and evaporating then recover and refine at the end of your career.

I've heard you refer to this in the past Harold. I wonder how many folks paid attention.

I'm new to refining for others and I'm not sure what to do with these extra values.

Thank you,

kadriver

Kevin in small lots and amounts of values I'd forget them, if larger amounts show unless the customer wants to pay for a full refine just give back any powders that didn't dissolve, silver much the same unless there is bib amounts it's just another small bonus.
Keep any recovered values and only worry about them if you either have quantities or no other work. The silver can go into the cell to add to what you already process the PGMs I'd only refine if you have serious amounts because as you know it's not the easiest material to refine.

Commercial refiners I've seen often set thresholds. They only payout when the amounts in a lot meet those thresholds. If they fall below, it is retained by the refiner.

As Nick has mentioned, trying to refine and return tiny amounts of every metal from every lot will cost a lot more time and materials.

Dave

I'm trying to find Harold_V's PDF, searched down till 8th September 2008 but no luck yet.
I'm quoting the post as I didn't won't to resume it after 6 years:

Harold_V said:

gustavus said:

Palladium said:

gustavus said:

Read the attached file, written by Harold_V inside an excellent description on processing jewelers wastes aka bench sweeps.

Click to expand...

I had forgotten how good that pdf was. Great work Gus.

Click to expand...

Maybe Harold_V would consider attaching the file to his siggy. HAROLD.

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A kind thought, but I don't want to appear to be promoting myself.

Harold

Click to expand...

The attached document wasn't there, is it still available.

Edit: corrected search date.

kadriver said:

Did you keep all the silver and PGMs recovered, or give credit (or the metal) back to the customer?

There was about an ounce of silver in the filings and maybe 1/10 gram (estimated) of PGMs left over after the gold was recovered.

I told the customer and he said he wasn't worried about them.

What did you folks do with these values?

Click to expand...

Platinum group; while they are valuable, they are, typically, just present in traces. That's not always true, for there are exceptions.
I told my customers that unless there was identifiable platinum group metals present in sufficient quantity to warrant return, they would be lost to them. None had an issue with that, as the cost of determining the amount would typically exceed, by far, the value. You could consider dental gold as one of the sources, which I ran regularly.

For exceptions, such as when a customer submitted a platinum object, if they could reuse the platinum, it would be pickled until it fell apart. I did that free of charge, but kept anything that resulted from the pickling process (platinum dissolves very slowly, so not a lot is lost, but al solder is eliminated). The platinum object, now in several pieces, could be melted for recasting. Only a couple of my customers were involved in that process, however, so it was not commonly accomplished.

For those who didn't want clean platinum alloy in return, I'd accept their platinum and return 75% in gold. That may seem unreasonable, but when you try to sell your platinum, it will make sense.

In regards to silver, most of my customers weren't all that concerned (unless they were silversmiths), but I had a policy of returning silver, based on percentage. Some of my customers gave it back, but others used it for alloying, or other purposes. The amount isn't great, but it displays to your customer that you are not there to steal from them, that you are concerned about treating them fairly.

All in all, it's about trying to build trust between you, as a refiner (most of whom have a lousy reputation), and the customer, who is responsible for your success or failure (assuming you run an honest business).

The stock pot "retirement plan" is a good idea. Just keep adding and evaporating then recover and refine at the end of your career.

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What makes the most sense is that you don't spend time chasing traces of values, yet when the time comes to recover, you're rewarded very handsomely.

I've heard you refer to this in the past Harold. I wonder how many folks paid attention.

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I fully expect that precious few would have the sense to do as I did. Most folks live beyond their means---so they eagerly spend everything at their disposal, and beyond. While I never made a lot of money, I have always been well in control of spending. Money does not burn a hole in my pocket, so I was perfectly content to allow it to accumulate. That was even true of my gold holdings. I hadn't sold even a trace until I turned to refining for an income. At that point, I had no options, but even then I sold only that which was necessary.

Harold

MarcoP,
Is this what you are looking for?

butcher said:

MarcoP,
Is this what you are looking for?

Click to expand...

It has to be, thank you so much ... some more great readings a-head.

Thanks for all the replays about pay outs to the customer.

I had another batch of filings and I used the PDF and it went very well.

The fine mesh copper screen worked perfectly and made some nice fine particles.

I treated these with nitric boiling for about 3.5 hours.

The final addition of nitric made very little fumes (this took much longer than I expected).

There was some of the red iron oxide rouge from the buffing compound in with this batch.

I re-incinerated after the nitric treatment and then boiled in HCl to try and get this red iron out before dissolving the filings in AR.

The red follows the gold and it takes about three refinings to get it all out. I can tell because the filtrate from the final refining is completely clear and colorless.

This HCl boil is an experiment to see if this red iron oxide will by removed before dissolving.

One nice feature of hematite (the red rouge iron) is it will not easily oxidize even in strong acids, or acid solutions which will dissolve gold, and you can even dissolve gold leaving most of this iron compound behind.

Butcher,

The red kept following the gold. It would show in the filtrate after all the gold had been removed.

I kept dissolving and precipitating until the filtrate ran completely colorless (I filter the gold out after precipitation instead of waiting for it to settle completely to save time).

It took about three hours to do it but it was worth the piece of mind, knowing that the red was gone completely.

This experiment worked well. The hot HCl treatment, then rinsing with distilled water to remove as much of the iron as possible, seemed to completely eliminate all the red iron oxide junk.

After hot AR the solution was green instead of the red I am used to seeing.