A stamp reading 18KGP means that the jewelry is gold plated, so an 18KGP white gold item would be plated with 18 karat white gold. The metal underneath the gold is usually copper or silver, but these can diffuse into the gold and tarnish the color.
Copper has a nickel-plated layer before adding the gold, while silver metals usually have layers of copper and then nickel. The nickel is a barrier metal that can help stop the primary metal from ruining the finish of the gold. If the barrier metal is not used, it can take only a few months to a few years before the gold is tarnished.
Karat is a term used to describe the purity of the metal and 18 karat gold is gold mixed with other metals, making it 75 percent pure. Each karat represents 1/24th of the gold's purity, or 4.1667 percent. Twenty-four karat gold is the purest, and 12 karat gold is 50 percent pure. Gold jewelry is usually sold at between 9 and 18 karat, and in the U.S. the minimum value for gold is 10. Gold is mixed with other metals in jewelry because gold as a metal can be damaged easily. Twenty-four karat gold is usually reserved for ceremonial or display use.Learn More
Clean gold jewelry by soaking it in a mixture of mild dish soap and club soda for five minutes. Use a soft-bristle toothbrush to clean the crevices and settings. Rinse the jewelry with water, and dry it with a soft cloth.Full Answer >
Gold-plated jewelry consists of a lower-quality base metal coated with a very thin layer of gold through a chemical process, while gold-filled jewelry has a thicker layer of gold bonded to a base metal through heat and pressure. Although both gold-plated and gold-filled jewelry consist of a base layer covered with gold, they differ in the process used to attach the gold and the thickness of the gold.Full Answer >
As a measurement of purity, 750 fine gold contains pure gold in 750 parts and other base metals in 250 parts. This measurement means that 750 fine gold is 75 percent gold. Although the purity of gold is measured by karats in the United States and the United Kingdom, there are many European countries using the decimal system to indicate the parts per thousandths of pure metal for silver, gold and platinum alloys.Full Answer >
The number 925 stamped on a gold piece of jewelry usually means that the jewelry is not entirely gold; it is sterling silver that has been gold plated. The number normally indicates the purity of the silver used, not the quality of the gold.Full Answer >