# Confused Testing Karat Gold



## midaselm (Apr 11, 2013)

Hi All,

thanks again for this forum and to everyone who contributes . I have read Hokes books , and have been buying scrap karat gold jewellery for past 6 months and thought I was getting good at this , but yesterday bought a piece of gold that confuses me . Its a heavy mens 9k bracelet and is fully hallmarked . I recently bought a plated item in error and it took the application of acid direct to item to show a fizzing green reaction, and then the plate had worn off revealing a white base metal.

When buying the item I used the touchstone and the item passed no problem. Worried that the item may be heavy plated I repeated the touchstone test on the same link again scraping heavily , and made three lines from the gold. All passed the 9k acid test. Also looking at where i had scraped the item , the item seems gold beneath the outside ie, solid gold metal and no sign of white or copper base. Happy enough with results I bought it. 

Then I placed a drop of acid onto the item itself. This leaves a darkend area on the gold (reddish /brown ), and the acid that wiped off has a green colour . Worried I got some other items to test in same manner . A known 9k item, and a known plated item . On the touchstone the plated item disappears and the two 9 k items pass . i also tested the lines by adding silver test solution to them ( nitric / potassium ) the two 9 k don't fade.

When acid is directly put on the plated item if fizzes green , and the plating is removed. When applied to the known 9k item there is no reaction except the gold slightly darkens . Added to my new bracelet , the gold darkens but left for a while appears blueish green , but with no major fizzing like the plated item does. 

So i specific gravity tested the item . Its 61.6 g and i got displacement of 5.6g which would give density of 11, which I think is ok for 9k gold .

From what I read any green reaction to the acid means it's plated but is this true ? With the specific gravity test and passing the touchstone test passing can I presume from those tests that its just the copper in the 9k reacting and causing this ?

Thanks for your help !
K


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## goldsilverpro (Apr 11, 2013)

With 9K or 10K alloys, the nitric dissolves the copper and silver from the surface, leaving behind a brownish powder, which is gold. Since some copper dissolves, the nitric will turn a light greenish color. With higher karat gold, there will be no color change since the higher amount of gold will prevent attack of the base metals. 

I would file a notch on the edge and apply a drop of nitric. If it is a solid 9K or 10K alloy, the brown will appear uniformly down in the notch. If 14K, there will be no color change. If plated, there will be fizzing and the nitric will turn a more intense bluish or greenish color


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## midaselm (Apr 11, 2013)

Thanks GoldSilverpro,

will get my nitric out later and let you know how i get on .... much appreciated


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## Jhuff8181 (Apr 11, 2013)

goldsilverpro said:


> With 9K or 10K alloys, the nitric dissolves the copper and silver from the surface, leaving behind a brownish powder, which is gold. Since some copper dissolves, the nitric will turn a light greenish color. With higher karat gold, there will be no color change since the higher amount of gold will prevent attack of the base metals.
> 
> I would file a notch on the edge and apply a drop of nitric. If it is a solid 9K or 10K alloy, the brown will appear uniformly down in the notch. If 14K, there will be no color change. If plated, there will be fizzing and the nitric will turn a more intense bluish or greenish color



This sounds great but how can I tell the difference between plated and filled when testing? I have been processing jewelry marked as GF but I also have many pieces that are not marked but have the look of gold. I have tested some of them with a drop of 14k testing solution on the surface and seen no reaction. Then if I file a notch I can see a reaction to the base metal but not the surface. Since plated is dealt with in a cell and filled dealt with in Nitric isn't it important to know whether it is plated or filled?


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## goldsilverpro (Apr 11, 2013)

Gold filled will most always be marked unless it is scrap left over from making the object.


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## Jhuff8181 (Apr 12, 2013)

Thank you for your answer. Many pieces that I deal with are partial so its hard to tell if the mark is missing.


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## nickvc (Apr 13, 2013)

The thing to remember especially with lower karat alloys like 9 or 10 k is that the base metal contents can be very varied, in traditional British 9 k there is around 10% silver in a yellow alloy but imported goods frequently have no silver and more copper and zinc, Italian chain rarely has silver in its makeup and can give slightly different reactions to the test acids. If the piece has a proper hallmark applied by the assay offices then I'd say it's pretty certain that its ok, they don't mess up often.


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## midaselm (Apr 17, 2013)

Thanks Gold silver pro,

got the 68% nitric out , and applies it to 3 items, a known plated item, a know 9k and the items im worried about. When applied to plated object, it bubbled and went a very vivid blue green, when applied to the two 9 k items there was no fizzing, but there was a very faint green color when i wiped the nitric off both, but nothing like the plated items blue colour, but i presume this is the copper in the gold. 

So i'm happy enough that I have some real 9k . I should have really taken some photos. 

Thanks a million


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## midaselm (Apr 17, 2013)

thanks nickv aswell !!


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## KCGreg (Apr 19, 2013)

Have you considered purchasing an electronic tester? In my store I have both a Tri-Electronics GXL24 and an Auracle. I find the GXL24 to be a little more finnicky than the auracle. You have to keep it extremely clean and sometimes the gel tubes dont work very well but it is a decent tester. You also have to be careful using it to test small, thin chains as it will eat through them and cause damage and sometimes even break them. I can't say I have any complaints with the auracle but I haven't had it very long. I like it so far because I can use it with my laptop, Ipad or android phone and the pen is good for some 5,000 tests. So the manufacturer says. It's also provides a bit of a wow factor at gold parties. I got both of mine from ajstools.com. 

Some other advice I can impart when testing karat is to be extremely wary of class rings. Many of them are under karated. Jostens and Balfour are the worst offenders. Those two also have a bad habit of stamping plated rings with a karat stamp. Either that or a whole bunch I have tested were stamped by a dishonest person outside of the factory. You should also beware of any chains marked Italy 14K. Scrutinize these very carefully, they might be 14k gold or they might be 14k plate. If you don't have a magnet yet, it would be a great tool to have. It doesn't always weed out plated scrap but it will get alot of it. I've made more than my fair share of mistakes in testing gold scrap to buy so if I can be of any help, feel free to PM me anytime with questions  Hope this unsolicited additional info helps you out in your scrap buying!


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## Lawaia69 (Dec 13, 2017)

Hello have a 14 k white gold chain which was beginning to yellow as the rhodium plate was wearing .Had the plating removed which was by no means a easy task. Tried sanding it but to tough to get off so ended up reverse electroplating it and it worked as the acid attached the preplate .So now the chain is yellowish I suspect a low grade white alloy ( ie copper ,nickel , zinc) .I am looking to sell this chain which weighs over 4 ounces. Took it to local pawn shops who performed a acid test and the results where that the item is a fake when acid is applied to the mark on the teststone it has no reaction other than the line disappeared in less than 15 secs. After doing some research there seems to be conficting information on testing white gold on some sites it say the mark should disappear within 15 sec. And others say the mark should hold up as testing yellow gold.Anybody got any information on the correct way to test this item.Thanks


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## jimdoc (Dec 13, 2017)

The Pawnbrokers Guide to Testing Metals



http://goldrefiningforum.com/phpBB3/download/file.php?id=1765


Testing Precious Metals C. M. Hoke

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=25181


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## saadat68 (Sep 11, 2018)

Hi
I need an image or video from trace of 24k gold on touchstone because I am confused
Sounds like there isn't any more information like image or video about that
In a video from YouTube I saw a man that scratches 24k button on the touchstone and the 24k gold draws streaks on the stone like 18k and 14k
But in this site I read 24k gold don't draws any streak just some flakes 
Can someone get me and image from 24k gold trace on touchstone?

Image from YouTube (Right streaks is for 24k gold)
http://uupload.ir/files/000x_screenshot_2018-09-11-21-08-58-813_com.google.android.youtube.png


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## 4metals (Sep 11, 2018)

I have never seen test needles in excess of 22 karat. Pure gold (24 karat) will not react with nitric acid so why make a streak for something that will not react. The way most scrap gold buyers who buy jewelry by the piece work is they put the karat test needle streak they assume the piece is and then one below it. Then they run a streak of acid across all the karat streaks they have made and wait to see which reacts first. The lower the karat the sooner it reacts. And 24 karat won't react. 

I never used anything but nitric acid for streak tests, but some say use aqua regia for anything over 14 karat. I think they use different strength's of nitric for lower karats and aqua regia for higher karats according to the GIA but one acid always worked for me. 

This is the method described by the GIA. 
https://www.gia.edu/bench-tip-use-the-touchstone-method-for-testing-purity-karat-gold


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## saadat68 (Sep 12, 2018)

Thanks 4metals 
It is a very good video that explain a simpler method but it don't work for 24k gold because there isn't 24k needle and 24k acid(?)

I want to know how is 24k gold testing on touchstone
In other words I need an image and some more explanation about this section because I see good streaks from 24k gold in the stone in the above picture that I got from YouTube( maybe it is fake) 


> pure gold will not bite in to the stone. It will leave little flecks of gold on the stone


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## saadat68 (Sep 12, 2018)

4metals said:


> I have never seen test needles in excess of 22 karat. Pure gold (24 karat) will not react with nitric acid so why make a streak for something that will not react. The way most scrap gold buyers who buy jewelry by the piece work is they put the karat test needle streak they assume the piece is and then one below it. Then they run a streak of acid across all the karat streaks they have made and wait to see which reacts first. The lower the karat the sooner it reacts. And 24 karat won't react.
> 
> I never used anything but nitric acid for streak tests, but some say use aqua regia for anything over 14 karat. I think they use different strength's of nitric for lower karats and aqua regia for higher karats according to the GIA but one acid always worked for me.
> 
> ...


Which acid do I must for 24k?
I think there is no 24k acid in testing kit and in a video I saw nitric acid don't react with karat gold same 24k gold


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## nickvc (Sep 12, 2018)

Well if you use AR then you should get a good red stain from 24k but from 22k it will be more orange yellow if I remember correctly. I’d recommend lots of practice using different karat samples and a piece of fine gold so you can be precise in your assessment.


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## saadat68 (Sep 12, 2018)

Thanks 
I have two questions
1- AR means 22k acid here?
2- I read that 22k acid don't dissolve 22k gold streak so how much time acid need to react with 22k and 24k streaks on the stone?


Thank you


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