GOLD TEST NEEDLES Set of 5 - 10K, 14K, 18K, 22K Gold and Silver Manufature direct. Use with a test / touch stone and testing solutions to compare 10K 14K 18K 22K gold and silver to determine the carat of other unknown gold and Silver. Made in the USA ( United States of America ) How to test gold with Gold test needles: First rub the gold or silver piece you would like to test for gold karat or silver on the stone to make a short line. Then next to the first mark rub the needle nearest to the karat of the gold piece or silver in question. Guess if you don't know or just start comparing with the 10K gold test needle and work your way up to the higher karat gold test needles. For silver you would tret and view the color. Place a drop of acid test solution that matches the karat of the test needle rubbed on the stone. If the gold is the same karat or higher the color and appearance of the mark for the gold piece being tested will be the same as the mark from the gold test needle. If that gold piece is a lower karat the mark will dissolve faster and become fainter then disappear. If the Gold Piece being tested is of a higher karat then the test needle then the mark from the gold piece will dissolve slower, or not at all, then the mark from the gold test needle. The carat: (abbreviation ct or kt) is a measure of the purity of gold alloys. In the United States and Canada, the spelling karat is used. Definition copied from WikiPedia.org For Retail purchases please see one of our Distributors sites.