making gold testing solution

[goldsilverpro]

The ready-made test solutions are very inexpensive and easy to find. However, since the 14K and 18K both contain HCl and HNO3, chemical reactions occur between the two and their strength will tend to change over time. In my experience, every ready-made solution I've bought reacted a bit differently, as far as speed is concerned. This is probably due to age or the difference in the formulas used by the different manufacturers. But, since this is a COMPARISON method (not an absolute method) between a standard and an unknown, all of that doesn't make much difference unless the solution are quite old and are too slow. For this reason, the make up of the homemade solutions don't have to be terribly precise.

 

[kmggold]

Interesting post. For determining purity of mixed karat scrap gold jewellery items using acid testing, I find the following to be essential.
Low karat gold I use nitric acid only, technical grade, assay 65-75%. The rate of dissolution and colour change is typically enough to determine 8-14 karat. Nitric alone will differentiate between pre-1982 14k stamped items that are 13.5k and 14k plumb. Nitric alone will immediately determine fake Hong Kong plated junk stamped 10k and 14k.
Then for the mid karat items I use a mixture of water, nitric and hydrochloric - one part hydrochloric, fifty parts nitric, and 12 parts water. This will immediately dissolve the lower karat stuff and slowly dissolve the 14-18k range. You have to be quick, but there is enough time to differentiate between 14k jewelry, dental, 17.5k (pre-1982), 18k, and some placer gold (nuggets). Once again the rate of dissolution and color change is significant enough to determine purity with good confidence.
Some literature suggests that testing higher karat material with acids loses accuracy. I have found this to be true, but only with bought, pre-mixed bottles of acid. Home made agua regia and quasi-aqua regia produces excellent results when prepared and used fresh. It is far to strong for purities less than 18k and will dissolve immediately on contact.
I use three different recipes for the high karats and platinum. Two "high test" recipes, and one of true aqua regia.
These are very very dangerous - handle with care! They will burn everything including you!
ALWAYS ADD ACID TO WATER - NEVER ADD WATER TO ACID!
one part nitric, 3 parts hydrochloric
one part nitric, 4 parts hydrochloric
and true agua regia, 9 parts nitric and 41 parts hydrochloric.
These will test, very accurately, all karat gold between 18k and 24k. Once again, by comparing dissolution rates and color changes. Although color change at high karat can be minimal. I also look at the scratch with a loupe to look for bubbling of alloyed copper and zinc, and white residue from alloyed silver.
For testing high karats I will use one line of each acid on all samples to quickly (very quickly if the karat is 22k or less) determine relative purity.
Using fresh homemade batches of acid can accurately differentiate between the sub-standard undercarated material from India, stamped 22k, but in reality is somewhere between 18k and 19k. There has been pounds and pounds of this stuff surface in Vancouver, Edmonton and Toronto. A lot of gold buyers took a hit on these items because they did not know how to accurately test the high karats.
When testing pure gold, if you have enough experience, you don't even need acid. Simply making the scratch with pure gold on a touchstone will tell you its pure. Alloyed gold "draws" on the stone like a pencil on paper. Pure gold will not "draw", it merely leaves very small flakes of gold on the stone.
If all you test is 10k, 14k, and 18k, then the bought, pre-mixed bottles may work for you. But don't use them on high karat or you might get burned!
All acid testing is relative to your known samples - so keep good reference samples!
I hope this helps. Please visit our web page http://www.kmggold.com for more information in our FAQ pages.
Mike

 

[slouma37]

Hi all,
as histonishing as it appears, i sometimes simply use a ceramic stripped CPU as a touch stone. It works just great ! Another way of recycling ceramic cpu's ? LMAO as a little touch stone cost's like 13€ like 18 US$ in Belgium.

Salim

 

[kmggold]

A very inexpensive alternative to a "touchstone" is a piece of frosted (sandblasted) glass. Available at most recycled building supply shops and occasionally at the Goodwill, Salvation Army thrift stores etc.
You can also buy this type of glass at building hardware stores.
Dark coloured glass is best for ease of anaysis...
You only need a small square of it.
Mike
http://www.kmggold.com

 

[newb]

Are there more solution formulas?
I found the answer of formulas to 18K but I'd like more, ie 20, 22, 24k

10K - 3/4 ounce, by volume, nitric acid - 1/4 ounce distilled water
14K - 4/5 ounce nitric acid - 1/5 ounce dist. water - 10 drops of hydrochloric acid
18K - 1/5 ounce nitric acid - 1/5 ounce dist. water - 3/5 ounce hydrochloric acid

Does anyone know the formulas for 20,22,and 24???????? either in oz, ml or drops will do.

 

[newb]

One says
18KT - 5.9 mL nitric - 5.9mL distilled water - 17.8 mL hydrochloric

The another says
18K - 5.9ml nitric to 5.9ml distilled water to 22.2ml HCL
for 22K i just used 1 part nitric to 4 parts HCL

Surely there's a standard somewhere right??
Where & what is it??

 

[samuel-a]

One says
18KT - 5.9 mL nitric - 5.9mL distilled water - 17.8 mL hydrochloric

The another says
18K - 5.9ml nitric to 5.9ml distilled water to 22.2ml HCL
for 22K i just used 1 part nitric to 4 parts HCL

Surely there's a standard somewhere right??
Where & what is it??

newb

Layoff the idea of having a "standart" testing solution for a specific karatage... It's all about comparison with your standart 18K 21K 22K needles (or other gold standart you have).
It' doesn't really matter what's the ratio of the AR you make, the reaction time is the point here. :idea:

 

[newb]

Reaction time??
I picked the name newb because I am just that. A newb to gold testing and solutions.
I'm trying to learn how to test the K of gold and make my own solutions to do so. There's not a book on it or a class to attend here so I'm looking online.
Any and all advise on learning this will be appreciated.

 

[samuel-a]

Reaction time??
I picked the name newb because I am just that. A newb to gold testing and solutions.
I'm trying to learn how to test the K of gold and make my own solutions to do so. There's not a book on it or a class to attend here so I'm looking online.
Any and all advise on learning this will be appreciated.

The point of which the test strike dissipate, in comparison to that of your standart karat piece.

 

[qst42know]

Reaction time??
I picked the name newb because I am just that. A newb to gold testing and solutions.
I'm trying to learn how to test the K of gold and make my own solutions to do so. There's not a book on it or a class to attend here so I'm looking online.
Any and all advise on learning this will be appreciated.

Here is a good explaination.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=3624#p30753

 

[bogarasjoe]

Hello guys!

Have you some information about 8 karat test solution? What concentration of nitric is applied?
I've read the 10 karat solution recipe, maybe it would work on 8k. But what about the 8 k test solution?

 

[butcher]

If you used an 8 karat gold needle to make a scratch on your stone, and a scratch from the suspected jewelry next to it, (a 10K needle could also be used to see if it was below 10K), and then used the 10k testing solution on both marks to see if one dissolved before the other or both stay the same, you could determine if the jewelry was 8K or not, then you could retest with other karat gold needles to see if it may be higher percentage of gold or not.

Search for a post by Pawnbroker Bob (Pawnbrokers guide to testing jewelry is a very handy few pages to learn testing jewelry) he goes into great detail with what you are looking for, Hoke's also has a book on testing.

I know a gold buyer who is very good at testing for gold and he is also good at telling the karat, and all he uses is nitric acid and a scratch of the jewelry on a black volcanic glass stone (no test needle scratch used), he can recognize the karat by how the nitric acid reacts to the gold scratch, by how much copper and silver and base metals the nitric dissolves and how much gold is left, he has been testing this way for many years, and is very good at it.

 

[bogarasjoe]

Thanks butcher for useful infos!
Unfortunately, i don't have test stone and needles.
I have just nitric acid, and a mini Maria Theresia coin. I dropped a very little nitric on it. The coin has gone brownish, not green. So i think it is gold, not just a gilded copper one. I found on the internet a same coin, and they are saying it is 8 karats.
A jeweler tested it with 14 karats test probe, but it was negative. So it is maybe less karat (or gilded copper? dont think).

 

[butcher]

If you have a ceramic CPU you could use it for a stone, a rough part of an old ceramic plate, or the rough area of the bottom of your black ceramic coffee cup would work also, the test scratch could be from another piece of jewelry of known karat, this would give you something to compare it to, or you could just try to decipher the scratch for your coin alone, you would see the scratch fade as the base metals dissolved in the nitric, he drop of acid turning blue to green in the acid, a little over half of the scratch would dissolve if the coin was around 8k, but should not fade completely away if gold is left from the coin, also you would not want any chlorides in the nitric acid you were using for testing with, I would not use homemade nitric acid, (unless it was distilled and silver nitrate was used to remove any chlorides).

I am not the best source for answering questions on testing jewelry.

Pawn Broker Bobs little book on testing metals is what you need.

 

[bogarasjoe]

LoL butcher!!! Ceramic CPU for test stone..... Excellent idea!!!!! Of course i have .
Test is comming soon. I'll try it with the 10 K test solution on a ceramic piece.
Thanks a lot!
Regards, Dave