Practical Acid Kit Silver Platinum Gold Testing Touchstone Jewelry Tool SetFeatures: This kit is used to verify the gold content in items<br> Ideal for testing jewelry, coins, antique gold, silver, platinum collectibles, and more<br> This solution works for testing any gold which you believe to be 10K, 14K, 18K, 22-24K, silver, and platinum pure. Acid changes color based on purity. Very easy to use. Specification:Material: High purity Graphite Stone & Acid Testing WaterGraphite Stone Size: Approx. 4.1 * 1.1 * 7.2cm / 1.61 * 0.43 * 2.83inchAcid Testing Water Size: Approx. 3 * 1.2 * 4.7cm / 1.18 * 0.47 * 1.85inchTotal Weight: 90gType: Jewelry Tools & EquipmentsPackage List:1 * Graphite Stone3ml * Acid Testing WaterNote:How to use:If you want test your gold ring is real or not, just need rub black stone, and leave a small sample on stoneApply a drop of this solution to a small sample of the item to be tested onto the test stone.Then the real gold will stay on the touchstone, false one will be dissolved or oxidized to blueIf the sample disappears, then the item is below the karat of the solution.