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Procedures for Testing Gold, Platinum and Silver

To test for the karat value of gold, platinum and silver, you will need the following materials and tools:

  • Black acid testing stone that is washed thoroughly with water prior to each test.
  • Acids
  • Gold testing needles with gold tips - used for comparison with test pieces.

Testing for 10K, 12K and 14K

Scratch the piece to be tested over the black stone if provided, press hard so as to leave a Large and Thick Visible deposit, preferably a line of one-half inch long. Next to this position, scratch the appropriate needle (10, 12, or 14K) if you do not have needles you can use a gold item that you know the karat of. Now Place a drop of the appropriate acid (same solution as the needle) on the stone where the gold was rubbed on. If the gold is the same karat or higher, the color of the scratch mark for the gold piece will appear the same as the mark from the needle. If that gold piece is of a lower karat, the scratched deposit will dissolve and eventually disappear while the scratch from the needle will stay.

By repeated trial, the karat of the gold pieces can be determined to a close approximation.

(Cation: Many objests are marked 14K, but were fabricated prior to 1982 when it was legal to mark items 14K, but in reality the gold was 13.5K When testing 13.5K gold the 14K solution will not dissolve the scratch, but will make it lose its brightness and will turn it into a yellow-rusty color)

On items of heavy weight and volume such as chains, coins, etc, where plating could hide the true metal, it is recommended that a deep notch in the test piece be made and the testing be made with the metal inside the piece.


Testing for 18K

Repeat the steps from  above and apply 18K acid. Any gold that is less than 18K will disappear in less than 30 seconds. Gold that remains on the stone is 18K or higher.

Testing for 20K and 24K

Scratch the test piece on the stone. Next, scratch any item of known karat (coin or needle) on the stone. Apply one drop of acid to area. The material that starts to disappear first has the lower karat.

Testing for Platinum

Scratch the test piece on the stone and apply one drop of Platinum Testing Acid to the application on the stone. If the material is platinum, it should keep it's white, bright color.

Testing for White Gold

The same procedure and Testing Acid for platinum can be used for 18K white gold . The material on the stone should start changing to a light bronze color in about three minutes. For 14K white gold, the material on the stone should disappear in 15 seconds.

Testing for Silver

Scratch the piece to be tested over the black stone if provided, press will so as to leave a Large and Thick Visible deposit, preferably a line of one-half inch long. If you do not have a testing stone it is possible to test directly on the piece to be tested. You will need to file a notch in the item and apply a drop of the silver testing solution to the notch.

Fine Silver - Bright Red                 

925 Silver - Dark Red

800 Silver - Brown

500 Silver - Green

Take into consideraation the background of the test stone is black this will make the color reation of the solution with the metal scratch will be more of a.

Fine and 925 SIlver - Creamy Color

800 Silver - Gray Color

500 Silver - Light Green Color

Note: With the silver solution, when testing directly on the piece wth solution will bull the polishing of the piece, and may leave a mark where the acid was placed.

 

 

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