18K Gold Acid Testing Solution 1/2 oz Bottle Gold Jewelry Testing Instructions for 10K, 14K, 18K, and 22K Gold: Scratch or rub the metal you are testing onto the stone.Scratch hard enough to make a visible streak or mark onto the stone.You may also shave the metal you are testing, and use the shavings to test onto the stone. Place half a drop of the closest acid to the karat you estimate the metal to be, onto the gold that rubbed off onto the testing stone. If the acid dissolves the metal, the metal is less than the karat that is displayed on the bottle. You should try again with a lower level acid. If it dissolves the metal slowly, it is possible that your material is gold, just not as pure as the karat rating on the bottle. If the metal stays and does not dissolve, it is at least the karat of the acid in the bottle. Great for testing Gold Jewelry, Bullion, Bars, Ingots Etc.. Please contact us with any questions.