This kit is designed to test the purity of gold items. The set is intended for use with gold only. The testing acid changes color according to the gold's purity. Simple to use: apply a drop of the testing solution to a small sample of the item on the included test stone. The kit includes a high-purity graphite test stone and acid testing solution. Material: High-purity graphite stone and acid testing water Graphite stone size: Approx. 4.1 x 1.1 x 7.2 cm (1.61 x 0.43 x 2.83 in) Acid testing water bottle size: Approx. 3 x 1.2 x 4.7 cm (1.18 x 0.47 x 1.85 in) Total weight: 90g Type: Jewelry testing tool Package includes: 1 x Graphite test stone 1 x 3ml acid testing solution Instructions: To test a gold item, rub the item on the test stone to leave a streak. Apply a drop of the testing solution to the streak. Observe the reaction: genuine gold will remain unchanged, while other materials may discolor or dissolve. If the mark disappears, the item is not pure gold or is below the tested karat level.