Gold in its purest form (24 karat) is extremely soft, so it's usually mixed with other metals like silver, copper, nickel or palladium to create a more durable alloy suitable for jewellery. The amount of pure gold present determines the karat value, commonly ranging from 9 karat to 24 karat.
Note: All of the tools mentioned below (magnets, acid testing kits, electronic testers) are widely available online from major retailers like Amazon, and higher quality tools generally give more accurate and consistent results.
Check for Hallmarks
Before using any testing equipment, examine your jewellery carefully with a magnifying glass or jeweller's loupe. Look inside rings, near clasps on necklaces and bracelets, or on the posts of earrings for small stampings. You'll typically find karat markings like 9K, 10K, 14K, 18K or 24K, which indicate the gold purity.
You might also see letter markings like "GF" (gold filled), "GP" (gold plated), "RGP" (rolled gold plate) or "HGE" (heavy gold electroplate), which mean the item is not solid gold. However, hallmarks can be faked or incorrect, so they're just a starting point, not definitive proof.
Magnet Test
Real gold is not magnetic, making this the quickest initial screening test. Use a strong neodymium magnet (not a fridge magnet, which isn't powerful enough) and bring it close to your gold item. If it's attracted to the magnet, it's definitely not solid gold, though it could be gold-plated over a magnetic base metal. If there's no attraction, your item passes this first test, but you'll need additional methods to confirm it's genuine gold.
Float Test
Drop your gold item into a glass of water and observe what happens. Real gold is dense and heavy, so it will sink straight to the bottom. If it floats or hovers in the water, it's not gold. This test is quick and non-destructive, though some other heavy metals will also sink, so you'll need to combine this with other tests for confirmation.
Acid Testing Kit
A gold acid testing kit provides the most reliable at-home method for determining both authenticity and karat purity. These kits include a testing stone (usually black), acid solutions for different karats (10K, 14K, 18K, 22K), and sometimes testing needles with known gold samples.
To use the kit, first scratch your gold item firmly across the testing stone in an inconspicuous area, leaving a visible gold streak. Then apply a drop of acid to the streak, starting with the karat you suspect. If the streak dissolves or changes colour significantly, your item is lower than that karat or not gold at all. If the streak remains intact and bright, it's at least that karat. Test multiple karat levels to narrow down the exact purity. For example, if the streak survives 10K acid but dissolves under 14K acid, you likely have 10K gold.
Important safety notes: Always wear protective gloves when handling acids, work in a well-ventilated area, and keep baking soda nearby to neutralise any spills. Apply acid only to the streak on the stone, never directly to your jewellery. For heavy items like chains that might be plated, file a small notch in a hidden area to test the metal beneath the surface.
Electronic Gold Tester (Optional)
For frequent testing, an electronic gold tester measures electrical conductivity to determine karat without using acids or making scratches. These devices cost between $50 to $500 depending on quality and features, and provide results in seconds by placing a probe against the gold surface. Electronic testers are clean, fast and non-destructive, making them ideal if you regularly need to test gold items.
However, they only test the surface, so you'll still need to file through any plating on suspect items. They also require calibration with a known gold sample (usually 18K) to maintain accuracy, and the probes need replacing every few months with regular use.
Thanks for reading! Jared & Brie