This set is perfect for anyone who enjoys buying/selling/trading/investing in gold, silver, and platinum jewelry and other precious metals. THE ACID TEST: Rub your sample (jewelry, coin) on the testing stone. This will leave a sample residue on the stone which you will apply one drop of solution onto for testing. --For Platinum: Apply one drop of platinum-testing acid onto the residue streak on your stone. If the material is platinum, material will retain its bright, white color. --For Silver: Acid test color reader: 90% - 100% = DARK RED 80% - 90% = LIGHT RED or brownish 65% - 75% = Light Green Color --For GOLD: Apply a small drop of the solution with the same purity you guess your sample to be. **If the sample residue remains unaltered, your sample is the purity for which you tested. If the acid you use dissolves the metal, your sample is less pure than you tested for; test again with less pure solution. *If your residue dissolves slowly, it’s possible your sample is slightly less than the purity you tested for.