todays Refined gold!

[jewelerdave]

Gave a bath to some of my bench sweeps, a couple old rings, some lathe shavings and a the 10k plate I pealed off of a rusty old pocket knife I found with a metal detector. A few customer rings that people wanted that gold put into there new rings.
The result was a nice button of just over 35 grams of fine
tomorrow it gets cast into new rings

 

[Harold_V]

Interesting.

What process did you use? The color appears to be off, but that could be the photo. I'd have expected a more yellow cast for properly refined gold.

Has it been pickled? What does it look like when heated without flux, if so?

Harold

 

[goldsilverpro]

It doesn't look too swift to me either. Of course, since you're using the gold for jewelry, the retention of a little copper and silver wouldn't cause problems. Lead would be the main problem, if present, and I'm sure you're removing that in the, uh, "refining" process.

 

[mike.fortin]

Gave a bath to some of my bench sweeps, a couple old rings, some lathe shavings and a the 10k plate I pealed off of a rusty old pocket knife I found with a metal detector. A few customer rings that people wanted that gold put into there new rings.
The result was a nice button of just over 35 grams of fine
tomorrow it gets cast into new rings

Dave--nice! How many rings you think that makes for you? 3? More? Hope you put up the picturs of your casted rings for us to look at? i like yuor scale. it wieghs in troy and av. What model is that? mine only wieghs in av. Mike.

 

[lazersteve]

The size also appears larger than I would expect for 35 grams of high purity gold.

Of course, no scale of reference is given, so it's hard to judge by size.

 

[jewelerdave]

Ok, here is a better pic that is not with the crappy cam on my cell phone, this one was done with a real cam with better light, it always comes out this color for me and has consistently assayed .99 or better
I use Aqua regia. dropped with Sodium bi meta sulfate.
the solution is rinsed several times, Fortunately in Colorado we have very pure tap water with almost no traces in it. Its then rinsed with ammonia to take off any copper stuck to the precipitate. A blue liquid is the result.
Then rinsed a few times more and then melted with oxy/propane so its a clean flame, sometimes we use oxy hydrogen flame.
We let it start cooling and dump a pinch of jewelers grade casting flux.
while its semi solid and bright red we dump it in water to quench it, and this breaks the flux off, then a rinse under water to get any remaining flux of.
Then we weight it, and chop it up with bolt cutters and alloy it back down.

Sometimes we cast it into a mold if I feel like heating the mold up.

Oh yeah, a good tip if your casting into a metal mold, heat it up to a couple hundred degrees before you dump the hot metal in there. Otherwise when the hot metal hits it will cause water to condense on the mold and it will turn to steam and blow up and a good amount of hot metal will fly up and out and around and you can lose it. Just heat it in an oven to drive off condensation. The heat has to be even and not done with your torch, a hot plate works to do the same thing. Hit a piece of iron with your torch and pull away and watch all the water droplets form from the differences in heat. I also coat my molds with a spray on boron Nitride witch helps keep the mold from rusting from the heating.

And to address the size issue, when you leave it in the crucible and let it cool often times the flux out gasses and causes bubbles in the gold, So its half hollow, again, since we are chopping it up the thin bubbly sections do not matter, when we pour it into a bar obviously its smaller in appearance.

 

[Noxx]

Much better pic...

But rinsing with water ? I don't see how water can dissolve unwanted metals... Or maybe you don't need to if you are looking for 99% purity.

 

[jewelerdave]

It does not rinse the metals out it just cleans any residual AR with dissolved metals in solution away.
For jewelry as long as its with in 7 thousands pure its legal as per the 1982 stamping act.

 

[Noxx]

What do you mean by 7 thousands pure ?
7/1000 max impurities ? This would be 99.993%+
Or maybe I'm wrong ?

 

[goldsilverpro]

I was under the impression that jewelry without solder had to be within 3/1000 (3 parts per 1000 parts) of the karat stamping. The 7/1000 tolerance figure pertains to jewelry that contains solder. Of course, gold solder is low karat. If solder is used, the initial purity of the gold being soldered would have to be a lot better than 7 parts per 1000 under karated.

http://uscode.house.gov/download/pls/15C8.txt

http://www.ftc.gov/bcp/guides/jewel-gd.shtm

6. Under the National Stamping Act, articles or parts made of gold or of gold alloy that contain no solder have a permissible tolerance of three parts per thousand. If the part tested contains solder, the permissible tolerance is seven parts per thousand. For full text, see 15 U.S.C. 295, et seq.

Noxx,

I am assuming this means parts per 1000 parts of 24 karat. Therefore, (3/1000) X 24 = .072 karats and (7/1000) X 24 = .168 karats. These are the quantities that the object can be under the karat stamping, depending on whether the object is without solder or with solder, respectively. In other words, gold stamped 14K, without solder, has to be at least 14 - .072 = 13.928 karats. That's the way I understand it.

There's another way to go about this, but you end up with the same final numbers. The fineness (parts per thousand) of plumb 14K gold is 14/24 X 1000 = 583.33 parts per thousand. Subtract 3 parts from this and you get 580.33 fine. The karat value of 580.33 fine gold is .58033 X 24 = 13.928. I think this is the way the gov calculates it in their pubs.

Before Oct. 1, 1981, the objects could be .5 karats under the stamped value. When buying karat gold scrap, you have to assume this figure since you have no idea when it was made.

 

[Harold_V]

What do you mean by 7 thousands pure ?
7/1000 max impurities ? This would be 99.993%+
Or maybe I'm wrong ?

It would be 99.3% purity, below industry standard (9995). Not acceptable in my opinion.

From the perspective of the benchman, the purity of gold used in jewelry isn't real critical, assuming the contaminants are the proper element, and in the proper state. That's not to say that the content won't effect the overall karat. It will, at least to a minor degree.

The real problem comes from what the contaminant is---and it's state. If you're contaminated with oxidized copper, the results are far worse than if contaminated with clean copper. assuming red or yellow gold is the objective. Gold contaminated with oxides tends to yield inclusions, the result of gassing. It's the primary reason for limiting the number of times alloyed gold is put to the torch.

If the contamination is lead, that may very well be enough to destroy the properties of the gold, yielding brittle castings that would not permit bead setting or rolling of ingots to prepare sheet gold.

Traces of silver in gold used for preparing white gold isn't the best scenario.

The very best proposition is to take extreme pride in the refining you do, following prescribed procedures and using good judgment. Washing the gold is of particular importance, for it's the only way you can get around the mechanical drag-down from precipitation. My procedure was to wash well, then re-refine the gold. The outcome was outstanding.

It takes a great deal to dazzle me where gold refining is concerned. I concentrated my efforts on achieving a level of excellence---exceeding, routinely, the industry standard of 9995. I am less than impressed with anything less. It's just as easy to do it right as it is to slop through the process and achieve miserable results.

Keep in mind------when you refine, in a sense, you sign your name to the gold. That was a very strong motivating force for me, likely one that followed me from my previous trade, that of being a machinist/toolmaker.


Harold

 

[Joe]

I'd like to hear about the hydrogen torch. What do you think of it? Get water dropplets? Can you melt gold with hydrogen alone and no oxygen?

 

[jewelerdave]

Good thing I always alloy on the rich side of things No one bitches when its more pure than stated. Of curse some will, fortunately for us a lot of our gold is from our own scraps as the rings we make are quite wasteful and require a lot of lathe work. Ironicly enough we depend on the waste for the profit margin as we cut away so much to expose pattern. Even that said the prices we charge for what we do makes it all labor costs. no reason to skimp on gold. if we did we would be cheating ourselves! LOL
It is unfortunate how many people do screw people on the gold and they dont even know it, Just last week I had a ring in that was stamped 14k, was hand carved and "custom" who knows when, could have been 5 years ago, could have been 20, but when it was in the AR it did not dissolve right...damn, 10k
When I apprenticed the guy I worked for did some slimy crap like that, and it always bothered me. Tossing in a couple extra grains of alloying metal to "freshin it up". Witch it did, but so does flux. the cheap skate.

Anyway, It just goes to show when refining karat gold to always buy low. There have been many times where the yeild came in a lot lower than expected. Thank god for the profit margins otherwise I would have been out a lot when I started out early on.

 

[Harold_V]

we have very pure tap water with almost no traces in it.

It would be unlikely for water to contaminate refined gold unless it contained traces of metals. Even then, the amount absorbed would likely be in parts per million. Far lower than the contamination in the solution from which your gold is precipitated. The balance of the minerals don't appear to report in the final product.

The use of distilled water in refining is way, way over emphasized unless you're making test solutions or making electrolyte for a silver parting cell. I used tap water routinely when I refined, and got excellent results (as you can see, below). While I've posted this picture a few times before, it's a picture of gold shot I produced, and can offer for sale. To think it could be purchased for less than spot is daydreaming. Ain't gonna happen, and never did when I was in business. Why would anyone sell $100 bills for $95?

Keep in mind that the gold pictured was melted without flux, and was not pickled to improve color. I don't claim 4 9's, but it certainly must be close. (On the subject of no flux, the melting dish used to melt the gold is lined with a thin layer of borax to insure free pouring gold. The dish, after melting a few hundred ounces, typically had no discoloration aside from a purple hue, the result of colloidal gold.

Its then rinsed with ammonia to take off any copper stuck to the precipitate. A blue liquid is the result.

The ammonium hydroxide wash shouldn't yield much color. If it does, you're not accomplishing what is required of the pre-washes. I, too, used ammonium hydroxide, and rarely got so much as a trace of blue coloration. You should be doing a HCL wash before the ammonia, and one afterwards, too, if you expect good quality gold, especially from bench waste.

We let it start cooling and dump a pinch of jewelers grade casting flux.

Get it pure and that isn't necessary. You're disguising the oxides by that method, not purifying the gold. Been there, done that, got the T shirt. The best scenario is to eliminate, in refining, the trace elements that lower the quality.

Oh yeah, a good tip if your casting into a metal mold, heat it up to a couple hundred degrees before you dump the hot metal in there. Otherwise when the hot metal hits it will cause water to condense on the mold and it will turn to steam and blow up and a good amount of hot metal will fly up and out and around and you can lose it. Just heat it in an oven to drive off condensation. The heat has to be even and not done with your torch, a hot plate works to do the same thing. Hit a piece of iron with your torch and pull away and watch all the water droplets form from the differences in heat. I also coat my molds with a spray on boron Nitride witch helps keep the mold from rusting from the heating.

The safety tip is very much appreciated, but the principle involved, as you described it, is in error.

Heat does not cause moisture to form. The moisture on metals so heated is the result of combustion in the torch, which yields water. It condenses on the cool surface. All that is required to eliminate the problem is to preheat the mold until it is warmer than the boiling point of water, at which time there are no problems with steam explosions. That can be accomplished with the torch just as easily as any other system, and it's far more convenient. Preheat the mold, blacken it with acetylene, and cast the gold. Done deal.

I cast gold ingots routinely as I described. That process provides a uniform, smooth surface, yielding a much better looking ingot, and insulates the gold from intimate contact with the mold. My molds were all cast iron, so it was important to form a complete barrier to insure that the gold didn't make contact with the mold, contaminating the ingot. There is no better way than with an oxy/acet torch for that purpose. Use only acetylene (no oxygen) , and blacken your molds in a fume hood to control the soot that settles everywhere.

For your perusal, I've posted a picture of ingots, below.

Edit: The picture of ingots is a very old photo ( early 80's), scanned. The color balance is not good, but the gold quality was the equal of that in the picture of shot, above.

Harold

 

[Harold_V]

When I apprenticed the guy I worked for did some slimy crap like that, and it always bothered me. Tossing in a couple extra grains of alloying metal to "freshin it up".

Anyway, It just goes to show when refining karat gold to always buy low. There have been many times where the yeild came in a lot lower than expected. Thank god for the profit margins otherwise I would have been out a lot when I started out early on.

Heh!

One of my customers (who shall remain nameless because he's still very much in business) bragged that he routinely underkarated his gold. Sad, too, because he's a somewhat well known designer of jewelry and can make a decent living being honest. Some folks simply have to scam others in order to feel good about what they do.

I was in the gold business for over 20 years. The most valuable asset you can have is your reputation. Don't do anything to tarnish it is the best advice I can offer anyone. Bad news travels very fast in the jewelry business.

I used to use a small mechanical scale to settle with my clients, a scale that weighed slightly more than the real weight. I always provided a full measure, and rounded down when I marked the package. As you alluded, it's uncommon for anyone to call you when you've delivered too much, but you look real bad if you're a grain short.

Another customer called one day, telling me I had sent too much gold. The order was large, and the error (in his mind) was worth a few bucks, but between the scale error and rounding down, it was all rightfully his. I told him to keep the "extra" gold and have a good day. Talk about building good relations, all at no cost to the provider!

Harold

 

[Platdigger]

SWEET! Harold!
Now "that" is what I call good business.

 

[jewelerdave]

Harold, Thanks for the advice, It is a good things this forum exists so things can be improved upon and done right. I dont know why so many people think it has to be a "secret"

I will have to try the extra rinses of HCL before the ammonia, it sounds correct, also the mold water sounds correct too, I didnt take that into account, but It makes sense, I know you get some 8 gallons of water for ever gallon of gasoline burned. Propane burning would also yield water.

If I recall the water here has some 6 to 9 ppm, I know they have to add things to it for the tap water to keep things from growing in it but its almost nothing as its all snow melt right off the rockies.

And thats pretty sad to hear that a designer is under karating.
I guess most people will not test a couple thousand dollar designer piece to see if its accurate or not.

Does anyone know of a way to get a sample? it seems like it would not be very hard now days to drill a small piece off and laser it back up. Any labs offer refraction assay services?

 

[jimdoc]

Has anybody had any experience with one of these testers?;
http://www.worldoftest.com/goldtester.htm
Jim

 

[goldsilverpro]

LOTS OF MONEY for something you can do much, much cheaper. Buy an Ohaus Cent-O-Gram. It's a very accurate (.01 gram readability) mechanical scale with a built in specific gravity pan and hook. It will weigh up to 311 grams. I've seen them new, as low as $138 on the web. Shop around. The prices are all over the map. Ohaus also makes the Dial-O-Gram, which is a little more money. It's the same basic scale, except it's a little easier to use, once you learn how to use the vernier. Both of these are often sold on Ebay.

In the book I wrote 18 years ago, I included a chapter on the Specific Gravity testing of karat golds. Since then, I've had 2nd thoughts about the method. The problem is the wide variety of karat gold formulas used for a specific karat. The SG's of the various formulas for 10K golds, for example, can be all over the map. Every jewelry maker seems to have their own formula to get the color they like. This can be very confusing when using SG testing.

BTW, please don't PM me to ask about my book. It is being revised and I'll let you know when it's ready. At the rate it's going, that may take forever.

Were it me, I would still use the ancient notch test (destructive) and touchstone, if I were buying scrap. Some people like the testing pens but, I have read that they can produce inaccuracies.

 

[jewelerdave]

Ok.
I did a test to try Harolds Advice and as you said it worked just fine.
Did the Ar, washed it with water a few times, then with HCL, then did the ammonia, a very very very light blue, almost non existent color instead of the usual dark blue, rinsed again and melted,

you were right, no flux needed. I plopped her in water and this is the result, This one is 14.2 grams.

I also took the pic in sunlight so you could get the full glory.
Looks like I am gonna rinse form now on, worth doing.

Thanks,

David