# How to clean gold.



## catfish (Jul 17, 2007)

Folks we spend a lot of time discussing many different types of refining techniques and ideas. I am pleased with the refining techniques that I feel comfortable using and now I have became interested in trying to obtain purer gold than I did before.

I have read many good posts by Harold on obtaining pure gold and decided to take the time and perform all the steps that he has so graciously told us about.

I refine most all my gold in “poor man’s aqua regia” and obviously as you can see from the first photo that the end results are totally unsatisfactory. I have been using Harold’s cleaning method on all my gold now and are very satisfied with the results.

Photo 1 and 2 shows two small batches that I ran through AR for a beta test for determining the amount of gold in electronic scrap. 

I took both batches and boiled it in water for 5 minutes, boiled in hydrochloric acid for 5 minutes, then boiled in water for 5 minutes, boiled again in ammonium hydroxide for 5 minutes, boiled in water for 5 minutes, boiled in hydrochloric acid for 5 minutes, and then boiled in water for 5 minutes. See photos 3

After this washing process I ran the gold chloride through aqua regia again, but I precipitated it with iron sulfate this time and then ran the chloride through the same wash cycle as before. I then dried the chloride and accumulated enough of it to make a sizable nugget. 

I also took Harold’s advice and only put a very small amount of anhydrous borax in a new melting dish. I melted the gold in 5five separate buttons and then I added all them to gather and made the final nugget. I have made arrangement to have it assayed. It will cost me $25.00 so I decided to just make one nugget. It should all be the same I hope. See photo 4

Note how clean the melting dish came out after all the melting’s. I think this tells a person a lot about the quality of their gold by looking at the finished dish and the dark brown or green colors sometime you get. See photo 5

Again, I want to offer my sincere thanks to Harold for sharing all the many wonderful ideas and past experiences with us folks. Three months ago, I was just happy to be able to refine gold and was not too concerned about the quality of it. But now I want to be able to do much better than I used too.

Thanks Harold.


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## badastro (Jul 17, 2007)

Excellent results  

How many SCSI fingers and memory sticks did you use for those batches in the pictures? Where did you get that melting dish?


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## catfish (Jul 18, 2007)

astro:

one beta test was 50 sticks of DIMM 100 memory. The fingers yielded .4 grams of gold on first AR and .3 grams on final process.

Two beta test was 152 SCSI controller circuit boards fingers. The fingers yielded 1.2 grams of gold the first run and 1.1 grams on the second and finila process.

I am trying to make a tutorial on how to determine the amount of gold in circuit board scrap. These two tests were part of this exercise.

Catfish


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## Harold_V (Jul 18, 2007)

All,

I, too, would like to offer my thanks to those of you that have had enough confidence in me to follow my advice. I take precious little credit for the words I post, just repeating things that I learned from my extensive studying of Hoke along the way to becoming a refiner. There's not much new in gold refining, it's just a matter of following the recipe and using good work practice. 

I'd like to comment on the length of boil time when washing gold. I usually did not set time limits on my washing operations, and often would allow a solution to boil for a considerable length of time. When re-refining gold, a wash that lasted for a couple hours was not unusual. A close watch on what is happening will be most revealing, and is a good indicator of when to move to the next step. If the gold starts out quite dark, but you notice that prolonged boiling lightens the color, by all means, boil longer. Do the same thing for each and every repetition----it pays dividends in yielding a much higher quality of gold. You may not achieve that magical 4 9's we hear so much about, but you should be able to achieve better than 9995.

I couldn't help but notice a slight discoloration in the bottom of the melting dish in the pictures that were posted. Assuming the dish was used only for the gold in questions, I'd suggest the gold that was melted still had a trace of base metals included. The prolonged boiling may very well remove them, although there's no guarantee it would. Gold that is not contaminated will not discolor your dish aside from traces of colloidal gold, turning the flux a nice purple color over time. 

There are a couple signs you may wish to look for when melting your gold. If the surface is not shiny while the gold is molten, and you see a dull layer that is active, moving towards the edge of the button and being absorbed by the flux, there is no question the gold is not pure, although the degree of contamination may be miniscule. Pure gold will melt with no discoloration, no dullness, and freeze shiny and smooth (and yield the characteristic deep pipe), although with a crystalline structure on the surface, usually quite coarse. If it freezes with miniscule crystals and has a frosty appearance, it is contaminated with something---although it may or may not yield an oxide covered surface. Not all contaminants do. Silver, for example. Any discoloration or dullness is a sure sign of contamination. 

Melting gold under a complete borax flux cover has a tendency to yield gold that looks good, but it may not be as it appears. The flux cover will prevent the oxidation of included base metal traces, so the surface will show no signs of oxides. That doesn't mean they traces won't be included in the gold should you have it assayed, because borax doesn't have the appetite for clean metals as well as it does for metallic oxides. By melting without the flux cover, you increase the chance of oxidizing the unwanted traces, and the thin flux covering in your dish will then absorb them. That should explain the slight green tint you see in the bottom of the melting dish posted by catfish. Remember----gold does not oxidize under normal circumstances, so it can be melted without fear of forming oxides, assuming it is pure, and your melting procedure doesn't contaminate the batch. 

Excellent work, catfish. I hope you've enjoyed the journey towards perfection. 

I found the challenge of improving my gold quality an ongoing process, and was still seeking perfection when I sold my operation, in spite of having achieved a level of excellence of which I was very proud! I think you've all seen a picture of the gold shot I've posted a time or two. It represents the last batch of gold I processed before transferring ownership of my refining business to the buyer. The gold in the photo came from the shotting operation with no pickle necessary to improve appearance. I think I was getting very close to that magic 4 9's!.

Harold


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## Noxx (Jul 18, 2007)

Harold, I have no doubt of your experience. I really enjoy your participation to this forum  

Thanks !


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## mike.fortin (Jul 18, 2007)

catfish said:


> astro:
> Two beta test was 152 SCSI controller circuit boards fingers. The fingers yielded 1.2 grams of gold the first run and 1.1 grams on the second and finila process. Catfish



Catfish--thanks for your hard work to. I know what DIMM is but that SCSI one I dont know. Any picturs? I used to have a scsi plug on an old flat bed hp scanner I had once. Is there a control board in it? Thanks. Mike.


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## catfish (Jul 18, 2007)

Hi Mike:

The term SCSI is pronounced as sku-ze or skuzzy. SCSI means small computer system interface. SCSI was first introduced in the UNIX world for attaching peripheral devices to computers. SCSI provides for extremely faster data transmission rates than the standard serial or parallel ports. In reality, SCSI is an I/O bus rather than simply an interface.

I am an old UNIX guy. I forget that every body did not come up in the UNIX world.

Attached is a photo of the particular SCSI dual channel controller circuit board that I used as a test case. Also please note the small white pin socket connectors on the end of the board. The second photo is a sample of the gold one of the connectors produce. I have not refined these connectors yet.

Catfish


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## mike.fortin (Jul 18, 2007)

Catfish--thanks. That picturs helped lots. I see its a card I shoud look for in my old tower and not in the scanner part. Thanks again. Mike.


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## goldsilverpro (Jul 20, 2007)

I just hate to see you guys wasting money to have your pure gold assayed. The thing I have trouble getting across is that, with high purity gold, the accuracy of fire assay just isn't good enough, even though it's the most accurate direct method on the planet. There are quite a few things that affect this accuracy: the balance accuracy; the skill of the assayer; the purity of the silver used to inquart the gold; the purity of the lead foil; traces of microscopic dirt or slag in the sample; etc. None of these things are 100% without error. They are all present in every assay and they all add up to give a net error.

For example, let's look at only the balance (scale) error. Most assayers use a balance that reads to +/-, .0001 grams. The standard gold sample size is .2500 grams. Lets say you ran the assay and got a final gold weight of .2498 grams. This gives a purity of .2498/.2500 = .9992 gold or. 99.92%. However, due to the built in scale inaccuracy, the weight might range from .2497 to .2499. This gives a gold percentage range from .2497/.2500 = 99.88% to .2499/.2500 = 99.96%. This is quite a difference and doesn't even take into consideration the other sources of error.

If you run duplicate or quadruple samples, you average the answers, and get more accuracy. However, to do this costs more money.

Also, $25 for an assay is very low. They can't be spending much time, cost, or effort doing your assay. That same assay will cost $250 at the best assay labs. It's best to not let the people you're selling to to do your assays. It's possible that they actually didn't even run an assay. They could have just looked at the gold, held it to their forehead, made up a number, and charged you $25. I can't tell you how many times I've seen this happen. The amount of gold you're selling them is minuscule compared with their total business. If you want a high number, they'll give you a high number. No skin off their butt. They're going to buy it, no matter what.

The best, and cheapest, way for you to determine purity is to simply look at the bar. Make it a go/no-go thing. If it has large, well defined crystal, a deep pipe, brilliant deep color, non frosty surface, no discoloration, it's a go. If not, re-refine it.


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## badastro (Jul 20, 2007)

What is meant by a deep pipe? :shock:


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## goldsilverpro (Jul 20, 2007)

As Harold explained once, the gold shrinks when cooled and the result is a hole in the top surface of the gold, usually near the center. This hole is called a "pipe." The pipe is squarish as it meets the squarish crystals. The pipe doesn't appear unless the gold is very pure. The deeper it is, the purer the gold, it seems. On occasion, there will be two pipes.


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## Harold_V (Jul 20, 2007)

While one may not be able to distinguish 3 9's and a 5 as compared to 4 9's by observations of the surface of ingots or buttons, the features are very telling, as Chris alluded. Only when gold is very pure will it cool with a shiny surface, free of oxides, and then, and only then, will it cool, yielding the characteristic pipe. If gold cools with a slightly frosty surface, it is contaminated without doubt. The same applies to the flux coating of a melting dish. If the flux is discolored aside from a light purple cast, it is absorbing something that was not removed in refining. While continued heating will continue to improve the quality of the gold by the flux absorbing the oxides that form, it is a long, tedious process, and not worth the effort. If gold, when melted, is not up to an acceptable standard, the best thing to do is re-refine it-----which is best done while it's still in powder form, as precipitated. It dissolves readily. The only advantage that one may gain by melting, then re-digesting would be the removal, by flux, of some contaminant that has persisted in following the gold. Assuming one uses good and accepted practice in refining, that is not often the case, and would most likely be left behind when a second precipitant was chosen. 

I think I'd have to agree with Chris in not paying for assays for home refined gold. If you work with good habits, and watch the signs provided, you can turn out gold of exceptional quality----and keep the cost of assays to invest in more scrap, or to buy needed supplies to improve quality. 

Assuming you are still not sure of the quality of your gold, and you'd like to know if it could be improved, a simple test would be to re-melt a button of gold that has been previously melted in a flux covered dish. Melt this button on a piece of carbon, then allow it to cool. If it cools with no oxides on the surface, the quality is superb. If it cools with a frosty surface, even without oxides, it is contaminated, possibly with silver. Just remember the things that Chris has mentioned-----those features come only with very pure gold. 

Sorry to repeat myself, this was written in haste. 

Harold


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