While it is usually quite difficult to tell if diamonds are real or fake, a trained eye can spot a fake sometimes a mile away. If you do not want to spend thousands on real diamonds but want everyone to think you did, then you will need to take some steps to make your fake diamonds look as new and real as possible. Fake diamonds tend to cloud faster than real ones and lose their shine, but there are many ways to make them look bright and new again with just a little work.
Soak the fake diamonds in a solution of of water, detergent and ammonia. Use small amounts of detergent and ammonia--no more than 1 or 2 tablespoons in 1/2 cup of water. Do not use detergent with bleach. Not only will bleach damage real diamonds, but it can also turn fake ones yellow.
Scrub the entire piece of jewelry with a soft toothbrush. Ultimately, keeping the grime off the fake diamond and the setting will make it last longer and appear brighter and newer. Fake diamonds are not as tough as real ones, so be very gentle when you scrub and keep the diamond submerged to make it easier to get dust and dirt off.
Purchase fake diamonds in a real gold setting when possible. Yellow or white gold settings make it much harder to tell if a diamond is fake or real, while silver, which can tarnish, or a plated setting that may rub off make the entire piece of jewelry appear to be of poor construction and value. The longer the setting lasts, the newer the diamonds will appear.
Opt for mid-size diamonds instead of huge ones. Mid-size fake diamonds are easier to keep clean and draw a little less attention to themselves, which helps them remain new because they will be handled less. Also, blatantly enormous diamonds tend to make people assume that they are fake--even when they are real. Sticking with 2 carats or less will make your diamonds more believable.
Take off your jewelry when you are not going out. Fake diamonds wear out faster. Many fakes discolor quickly and their settings wear irreparably. Only wear your fake diamonds when you are going out and keep them in a safe, soft box when you are not wearing them. Do not wear them to clean or cook.