What is the definition for white gold-filled, yellow gold-filled, nickel-plated, and yellow-plated?

The term gold-filled refers to the manufacturing process in which a sheet of base metal, usually brass, is mechanically bonded with thinner sheets of gold. A "sandwich" is formed by mechanically bonding a layer of gold on both sides of brass. This "sandwich" is then cold worked by rolling until a much thinner gauge metal is achieved. Products are then formed or die-struck from this layered material.

When a layer of gold is affixed on all surfaces by any mechanical means and the weight of the gold is a minimum of 1/20 of the total weight of the metal in the article, it may be marked Gold-Filled (GF). The quality of the gold used is typically 10, 12 or 14 karat gold with 10 karat being minimum. Hallmarking would look like “10K GF” or “14K GF”. Yellow gold-filled or white gold-filled simply indicates the color of the karat gold used in the making of the gold-filled product.

The terms “Rolled Gold Plate” and “Gold Overlay” refer to the same bonding process; however, the weight of karat gold is less than 1/20 but not less than 1/40 of total weight of metal.  Hallmarking would look like “1/30 12K R.G.P”, “1/40 10K Gold Overlay”.

When a product is referred to as gold, rhodium, or nickel-plated, this indicates that it has been electroplated with a thin layer of that particular metal. An article of jewelry is Gold-Plated when gold is electroplated or mechanically sheathed with a mini­mum thickness of 1/2 micron (20 millionths of an inch) of fine gold. The quality of the gold used is typically 10, 12, or 14 karat. The karat quality of the gold plating must be disclosed, and it can be described as 12K Gold Plate or 2μ 12k G.P. for an item plated with two microns of 12 karat gold.

The table below lists all the different plating terms and their associated thicknesses.

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