The integrity of your metal’s quality is important. When buying precious metal scraps from your customers, you’ll need to ensure the composition of your salvaged assortments in order to maximize your profits. Read on to learn more about the different types of metal tests and determine which would work best for you.

First things first, why should you test the precious metals you intake anyway? Because your gold scraps may be underkarated…

• Jewelry created prior to 1976 was made to the old US jewelry standards, which were +/- 1/2 carat. In addition, karatage of soldered jewelry items could be within +/- 1 karat. This means 10K gold could potentially be as low as 9K (.375), 14K could be 13K (.5417), and 18K could be 17K (.7083).

• Most of the items made at this time were soldered with lower karat repair solders. It took several years and a number of under-karating lawsuits to bring everyone into compliance with the newer regulations.

• Much of the chain made in the 70s was heavily underkarated, especially since strict monitoring did not take place until the 80s.

They do have standards…

US Federal Standards for Plumb Karat Assay


Tolerance for gold articles = .003
Tolerance for gold soldered articles = .007

10K gold = 10/24ths gold (.4167)
     < .4137 = underkarated
     < . 4097 = underkarated (soldered)
14K gold = 14/24ths gold (.5833)
     < .5803 = underkarated
     < .5763 = underkarated (soldered)
18K gold = 18/24ths gold (.7500)
     < .7470 = underkarated
     < .7430 = underkarated (soldered)

So you’re ready to test your metals, what’s next?

Here are the pros and cons of three popular methods for metallurgical testing.

Acid Testing

Pros

Cons
 • Proven method - used for years • Dangerous chemicals involved
• Inexpensive • Messy process - will stain fingers yellow
  • Will destroy clothing
  • Will rust your tools
  • Extra shipping cost due to hazardous material (if shipped in volume)

Note: After testing, sample can be cleaned with 400 grit paper.


Electronic Testers

Pros

Cons
• Accurate on standard alloys • Must keep the tips clean
 • Quick and easy • Gel and pen probe replacement required
 • No mess! • Must clean jewelry before each test
  • Must scratch the sample
  • Some units require calibration periodically or each time the machine is turned on/off

Fire Assay

Pros

Cons
 • Most accurate at 0.01% and greater
 • Destroys the metal sample
• Legally approved in a court of law
 • Expensive setup costs
  • Takes several hours for results
  • Environmental setup expense
  • Health concerns (lead fumes, etc)

Note: Roughly 250mg is needed for sample.


Here at Stuller, we rely on the fire assay method because of its accuracy to ensure our customers receive the highest quality metals every time they buy from us. Check out the full process below, or visit Stuller.com/metalscenter to learn more.