It's simple - over time, your jewelry comes in contact with moisture, acids, oils and air. They react with the metal in the jewelry, causing it to eventually wear down and tarnish.
This is largely due to the fact that gold plating is a thin layer above a base metal, which makes pieces stronger and less likely to bend. Unfortunately, over time, the base metal will eventually come to the surface, causing the metal and the gold to discolor.
Another way to spot fake gold is that it can rust in high humidity or over time.
Fake gold can float or fall more slowly. Real gold also won't rust or tarnish when exposed to water, while gold plated items can show discoloration.
Vinegar is very destructive, so when you apply the vinegar to a fake piece of gold, the vinegar will cause the jewelry to tarnish. Gold is a non-reactive metal, so real pieces of gold will not react to vinegar.
On average, gold plated jewelry can last about two years before the gold plating begins to tarnish and wear down. However, the length of time can be much shorter or longer depending on whether or not you decide to properly maintain your jewelry collection.
Showering with 18k gold-plated jewelry is generally not recommended. The reason behind this this is that prolonged exposure to water and moisture can cause the gold plating to wear off more quickly, which can lead to tarnishing, discoloration, and other forms of damage.
Out of all of the options, gold plated pieces are the most affordable. However, because there is a thin layer of gold applied to a base metal, gold plating over time will wear away or can flake off.
It's simple: Solid gold never tarnishes, while faux gold—or gold-plated metal—does. If your jewelry has started to discolor and tarnish, or if it turns your skin blue or green where it comes in contact, then it's not solid gold.
Then, place your jewelry into a bowl and add a few drops of your vinegar into the bowl. Real gold will not change color, but fake gold will turn either black or green. Since vinegar is an acid, it will break down any chemicals that are in the jewelry.
Hidden copper inside metal jewelry is the most common reason your skin turns green. Costume jewelry labeled as being made of nickel and even pieces that are silver- or gold-plated often contain copper or copper alloys (a blend of metals that has copper as a component).
Scratch test.
If you cut deep enough that you expose underlying metal, you can assume that it is plated. If it appears to be made of a uniform composition throughout, then it is probably solid gold.
Cleaning fake jewelry in vinegar can leave the chains shiny. The soft bristle toothbrush can help if the jewelry contains gems by getting in cracks. You can simply apply the vinegar to a sponge, and use it to clean the jewelry.
Unlike real gold, costume jewelry can tarnish, but that doesn't mean it has to be thrown out!
Fool's gold is the most common of these. Better known as Iron Pyrite, this sulphide mineral is infamous for looking just close enough to gold to fool the untrained eye. Fool's gold is much less dense than the real thing however, so this is a very easy way to check between the two.
A float test using water is the easiest and safest way to tell if your gold is real at home. Start the process by taking a glass and filling it with water. Drop the gold accessory you want to test in the filled glass. If your gold piece sinks to the bottom of the glass, it is real.