To test for genuine gold, use bleach: It will not harm your genuine gold jewelry, but it will destroy any imitation gold jewelry. Although bleach is quite similar to nitric acid, it is not as accurate as a test. It can verify the authenticity of your gold, but it cannot tell you how pure it is. Gold objects that are coated with multiple layers of gold may look like they are worth money when tested with bleach, but these same objects would be destroyed by an acid test. The best way to check if your gold is fake or not is to have it tested by a laboratory. Testing methods include atomic absorption spectroscopy (AAS), gas chromatography (GC), and vaporization-chamber techniques such as neutron activation analysis (NAA) or thermal ionization mass spectrometry (TIMS). Gold objects that can't be tested directly should be sent to a laboratory for testing. The tests used by laboratories to determine the purity and quality of gold are expensive. So if you can afford it, we recommend that you have your gold tested by a reputable laboratory. Gold jewelry that has been cleaned using soap and water can be re-dyed using our guide here. If you want to learn more about how gold jewelry comes in different colors, take a look at this guide.