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Question about acid testing, x-ray testing

Mreader

Mreader

Ideal_Rock
Joined
Aug 14, 2018
Messages
6,876
I bought a necklace off a site that says they test their metals with xray - they called it a Thermo Scientific Niton XL2 or DXL, an industry standard x-ray center. The item was supposed to be 14k. When I got it, I tested it myself using a home acid test. I am showing a picture below. The right scratch is the clasp, the left scratch is the links of the necklace (I am referring to the long big scratches; I see there is another to the right but ignore that. I have been testing many things haha). The bottom acid is 10k, middle 14, top 18. So it's at least 10k because the lines show up super clearly. But they fade at 14, but they don't disappear completely. This is where acid testing gets confusing for me. I can see the lines, but not as clearly as 10. So does that mean it's between 10 and 14? Like 12? I decided to take it to a pawn shop (I actually bought the acid kit so that I wouldn't have to keep doing that lol) and they said it tested as 10k. They said it is NOT 14k.

So my question is - would the xray be unreliable? Based on my test, are the pawn shop ppl correct in asserting it isn't 14k? Is it somewhere in between? I would love to hear your thoughts. Tagging @Karl_K and if anyone else knows anyone to tag about this, let me know!

image0.jpeg
 
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Well I will get the ball rolling.
I dont know a lot about that machine so not going to say how reliable it is at determining how much % gold is present.
The acids on the other hand are tricky, they vary a lot brand to brand and lot to lot and can change over time.
Some of the old timers I used to haunt their stores kept reference sheets of different % to test a new batch and to verify the old stuff.
One would use references sheets to do side to side comparisons then testing a customers gold.

Here is a video on the Thermo Scientific Niton XL2

another video:
 
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Karl_K said:
Well I will get the ball rolling.
I dont know a lot about that machine so not going to say how reliable it is at determining how much % gold is present.
The acids on the other hand are tricky, they vary a lot brand to brand and lot to lot and can change over time.
Some of the old timers I used to haunt their stores kept reference sheets of different % to test a new batch and to verify the old stuff.
One would use references sheets to do side to side comparisons then testing a customers gold.

Here is a video on the Thermo Scientific Niton XL2
Click to expand...

Interesting. So there can be a lot of variation. And my acid kit was just a cheap $20 on eBay lol
 
But my other question is based on the photograph that you see, assuming that the acid is OK, does this pass the 14 K test? Even though the line is faded yet you can still see it? Or if it’s fading at all it’s under 14 but is it above 10? The second part of my question was about basically reading the acid test.
 
I watched a bunch of videos and they pretty much agree with this one which answers your question on fading lines.
 
Karl_K said:
I watched a bunch of videos and they pretty much agree with this one which answers your question on fading lines.
Click to expand...

That was very helpful!
 
You could ask them to sell you a chunk of tested 14k scrap to test your acid against theirs.
That would help your education.
Or if you have some scrap of your own to have tested....
 
Informative @Mreader
I always wondered!

And I also wonder what does the necklace link look like after the scratch test? Is it noticeable ?
 
Hi @Mreader
I don’t have a lot of experience with acid testing, but we have a number of XRF analyzers made by Thermo Fisher, and they are excellent, but with all machines, they have limitations (mostly when an item is heavily plated or coated)
When testing a standard 14K or 10K item, the readings are pretty straightforward and highly accurate and consistent
Before we could add metal testing to our ISO scope, we had to demonstrate that XRF was highly correlated to both fire assay testing and ICP testing, and it is
Can you get a screenshot of the XRF reading from the company that tells you it tested as 14K on the Thermo analyzer? The analyzers have internal memory that store up to the last 8,000-9,000 readings so if they really tested it, they would have a copy of the testing record
I would take XRF (done properly) over acid testing, all day long
Hope that helps - I know it doesn’t answer your acid question, but I can vouch for XRF testing being highly accurate
One example of when XRF is awful is when you have a heavy nickel plated silver item - instead of getting 92.5 % AG, you end up with 70% NI and 30% AG and unless you file or dremel it, you would never know
-Angelo
 
I have the $20 acid test kit too. I think it is reliable and easy to use, once you get the hang of it.
I always use a test piece of scrap gold, as well.
That video was pretty informative.
@Mreader , I think your streaks on the stone need to be much heavier, like the guy in the video shows. This way, you can get a good visual reading, and you can clearly see if the streaks are fading or not.
 
Rfisher said:
Informative @Mreader
I always wondered!

And I also wonder what does the necklace link look like after the scratch test? Is it noticeable ?
Click to expand...

No it wasn’t noticeable at all, but I didn’t really scratch super hard lol. As @stracci2000 said I probably need to scratch more. I think a truer test would involve putting a deliberate scratch in the metal itself and dripping acid on that, but I don’t want to to that to the item.
 
GCAL said:
Hi @Mreader
I don’t have a lot of experience with acid testing, but we have a number of XRF analyzers made by Thermo Fisher, and they are excellent, but with all machines, they have limitations (mostly when an item is heavily plated or coated)
When testing a standard 14K or 10K item, the readings are pretty straightforward and highly accurate and consistent
Before we could add metal testing to our ISO scope, we had to demonstrate that XRF was highly correlated to both fire assay testing and ICP testing, and it is
Can you get a screenshot of the XRF reading from the company that tells you it tested as 14K on the Thermo analyzer? The analyzers have internal memory that store up to the last 8,000-9,000 readings so if they really tested it, they would have a copy of the testing record
I would take XRF (done properly) over acid testing, all day long
Hope that helps - I know it doesn’t answer your acid question, but I can vouch for XRF testing being highly accurate
One example of when XRF is awful is when you have a heavy nickel plated silver item - instead of getting 92.5 % AG, you end up with 70% NI and 30% AG and unless you file or dremel it, you would never know
-Angelo
Click to expand...

Thank you for this info. So I contacted the company (which btw was Goodwill Shopping) and told them what happened and asked for a credit of some of what I paid because I still wanted to keep the necklace. They issued the credit without question. I don’t know if they did this because sometimes big companies just issue a credit like that without argument, or whether they knew their test was somehow flawed. I have no idea now! I’m going to be in a different city during Thanksgiving and I might take it somewhere else and see what their test says.
 
@Mreader
Can we see the necklace in question? Pretty please?
 
Mreader said:
No it wasn’t noticeable at all, but I didn’t really scratch super hard lol. As @stracci2000 said I probably need to scratch more. I think a truer test would involve putting a deliberate scratch in the metal itself and dripping acid on that, but I don’t want to to that to the item.
Click to expand...

I would never put the acid directly on a piece for fear of damage.
 
stracci2000 said:
I would never put the acid directly on a piece for fear of damage.
Click to expand...

Agree. I have just read about this, in case it’s a heavily plated item. But I wouldn’t risk it either.
 
Pretty necklace! Your experience was better than mine. I have bought a handful of things from Goodwill, one was plated that was advertised as 14k and the other was supposed to be 14k white was silver. The silver ring was stamped 14k on the inside of the band too but a jeweler confirmed it was silver, I knew right away something was off anyway.
 
YadaYadaYada said:
Pretty necklace! Your experience was better than mine. I have bought a handful of things from Goodwill, one was plated that was advertised as 14k and the other was supposed to be 14k white was silver. The silver ring was stamped 14k on the inside of the band too but a jeweler confirmed it was silver, I knew right away something was off anyway.
Click to expand...

Wow. Do you recall if they claimed that it was x-ray tested in the description? Were they good about a return ( I am assuming you returned)?
 
stracci2000 said:
Ahhhh! A big chunky one! I love those links!
So gorgeous!
Click to expand...

That is why I wanted to keep it! I was really hoping they would do what I asked and just issue a partial credit, which they did.
 
Mreader said:
Wow. Do you recall if they claimed that it was x-ray tested in the description? Were they good about a return ( I am assuming you returned)?
Click to expand...

I don’t remember whether they were x-ray tested. They were good about returning in both cases.
 
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