Testing/Refining Gold Embossing Powder

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hdowd

Member
Joined
Sep 26, 2016
Messages
9
A friend is retiring his century-old family printing business. He has a fair quantity of a variety of gold embossing powder of various eras and types. He'd like to know what he has and what he should do with it. Kitco says one powder has reasonable content but is difficult to refine. I've read the threads here from about 5 years ago but found nothing within our limited skill level.

Can anyone here with experience in testing and refining embossing powders offer advice about simple tests to reliably eliminate non-gold-bearing powders and test and refine gold-bearing powders? Or are the bearing powders worth more as powders?

Thanks.
 
Much gold coloured powder is brass so the best initial test is to use nitric acid, put a tiny amount of powder on a plate and add a drop or two of nitric, if it fumes and turns green/blue it is brass, if there is any powder left it could be gold, if you get no reaction or a very slow one it has the chances of having gold content.
If you struggle to get nitric buy some low karat testing solution off eBay which is fairly cheap, it will do the job.
Good luck and if you find some good well done 99% of the ones I have tested are copper based but real ones do exist, as to been hard to refine that's rubbish, it's very easy if you have the right chemicals, if you find some gold based powders come back and we can help you get it into a form you can Sel, without spending a fortune.
 
Thank you so much for your prompt reply, nickvc. I will get some nitric acid and give it a go.
 
Thanks, Lou. They seem to deal with refined versions only. Which is too bad because I have a small amount of some silver ore, as well.
 
nickvc said:
Good luck and if you find some good well done...as to been hard to refine that's rubbish, it's very easy if you have the right chemicals, if you find some gold based powders come back and we can help you get it into a form you can Sel, without spending a fortune.
That was my thought exactly. I was reading some old threads recently about some folks not inquarting their karat scrap, especially if they could get it good and thin. You can't ask for more thin than a finely divided powder!
 
Alrighy, then. I have received a gold testing kit for 10k and higher, But some of this material may be under 10k. How do I test it? I have distilled water.

This is a learning curve, for sure. Thanks.
 
One simple test would be to take a pinch and try to dissolve it in nitric acid. If it is entirely dissolved, it's not gold at all.

Be sure to start small (about 1mL nitric per gram of powder), then add nitric by the drop until the reaction stops. With water at least, by the way, 20 drops is about one mL.
 
Here are the results: 10K solution fizzed and left a gold film and 14K dissolved and left a trace of gold, even when more solution added.

So that means it tested positive for 10K, but am I right to think maybe a 10K powder was mixed with a higher K powder? It's an old print shop.

How do I refine a 10K powder safely and affordably?
 

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To me, that looks like your powder is in the 10-13K range. 10K test acid did not affect it (much), but the 14K acid just about ate it all up.

Since it's so finely divided (fine powder), it's possible you could do a straight AR digest. Part of it depends on what the rest of your alloy is--if there's sizable amounts of silver, that will turn to insoluble silver chloride in AR, which isn't awesome but it's workable. It all depends on the amount. If the balance of your alloy is just copper & zinc, you should be fine.

I would do a small test batch in AR and see how much (if any) silver chloride you get. If it's sizable, I suggest nitric first to pull off the base metals & silver, then AR. The other, more traditional, way would be to process it as Hoke would do karat scrap, via inquartation.

Don't go on my word alone, though--let's see what the others say.
 
Thanks Upcyclist!

AR = Aqua Regia? Will 22K test solution work in this case?

Should I treat with 10K solution and wash out with water to get a 10K powder? Or is that adding a preventable step? Ah, wait, or is 10K solution just nitric acid?
 
With very finely divided powder such as this I would suggest a dilute cool nitric digest, cover well with distilled water and slowly very slowly add small increments of nitric, allow reaction to cease and stir carefully once any further reaction ceases keep doing exactly the same, once the final addition of nitric has produced no reaction add heat slowly and stir if you get more reactions carry on adding small increments of acid until you get no reaction, if you have gold in the powder any material left should be high grade gold, if you had silver in the powders simply cement the filtered solution with copper to recover it.
 
There appears to be a water-soluble component to this. Is there a chance this is just 10K gold in a water soluble solution? Also, I see the gold floating, presumably due to surface tension and hydrophobia. As more gold is in the solution will it sink so I can just pour off?
 
It's simply not economical to buy the amount of testing solutions you'll need to process your powders--you need to be using hydrochloric & nitric acids to do it properly. Otherwise, you'll spend more in testing solution than you'll recover.

You've come in with some great questions--but I think you would be best served doing some research and reading Hoke. You'll also want to read up here on Safety, and hit the Guided Tour.

Here's a couple versions of Hoke (also found in FrugalRefiner's sig blocks):

Printer friendly copy of C. M. Hoke's Refining Precious Metal Wastes.
Screen readable copy of C. M. Hoke's Refining Precious Metal Wastes.

Another option is to find someone to do the work for you--if you ask, I'm sure you'll receive offers from members here.
 
Downloaded files and seeking materials. Thanks, Upcyclist!

The biggest question is more about what net he has, as shipping in Canada is the most cost prohibitive aspect for junk/low grade anything. If, for example, this sample is a high percentage of 10K in some easily extracted form, the options open up, but if at the end it's only a single viable tin of 100 grams carrying a single gram of 10K, I believe it makes it worth about $17.50 US minus time and expenses - not so attractive. So at this point we're just looking for ball park yield and ball park extractability, as there are a half dozen tins spanning a century. Since neither he nor I have the rig for extraction (much less the experience), the idea of sending the material to someone from this forum is certainly an attractive option.
 
I would not use the 14K test solution on powder, as it is a week form of AR.
Unless of course you are using enough powder and solution that you can later precip the dissolved gold, dry and weigh.
With enough experience you could compare dissolution rates with the 14K test solution, but that will take some experimenting by you.
 
I just realized that I don't know where to buy acids in Canada! You used to be able to get some kinds at hardware stores and hobby shops, but I remember decades ago that things changed and it was harder to get undiluted acids.

Anyone know where to buy it here?
 
I'm not in Canada, but here in the States you can find most of what you need in hardware stores--except nitric. You'll have to get that from scientific supply outfits.

Sent from my SAMSUNG-SM-G891A using Tapatalk
 
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