Gold-filled jewelry is a low-cost alternative to solid gold pieces and, in most cases, has the same appearance and may last for decades. Although the gold layer may eventually wear off, exposing the core metal, gold-filling is a much better option than gold plating.
The history of gold-filled jewelry traces back to the early 19th century England, where this technique was patented to create semi-precious and better-quality custom jewelry during the Victorian Era.
Gold-filled jewelry, also referred to as rolled gold plate or gold overlay, is jewelry composed of a solid gold layer of not less than 10 karat fineness and constitutes at least 1/20th of the item’s total metal weight, mechanically bonded to a core metal such as brass, copper or sterling silver.
The terms “gold overlay” and “rolled gold plate” may also be used in reference to the jewelry that is composed of less than 1/20th of solid gold in case the portion of the gold’s weight is accurately disclosed by a fraction, for example, 1/40th 12k rolled gold plate or 1/40th 12k RGP. In comparison, the term “gold-filled” may only be used in reference to jewelry that has a plating of solid gold of at least 5% of the item’s total metal weight.
The abbreviation used to stamp modern gold filled jewelry is GF standing for gold-filled. The most common stamps found today are 1/20 12k GF and 1/20 14k GF. Items can also be labelled 12/20 GF and 14/20 GF, which means the jewelry is gold filled with 12k or 14k gold. To indicate a rolled gold plate jewelry, jewelrs use RGP or R.G.P.
Unlike the gold plating process, the gold filling is made mechanically. First, the base metal is cleaned to remove any accumulated dirt. Then a layer of solid gold is mechanically bonded to the core metal using heat and pressure. The bong between the gold layer and the base metal is permanent, meaning the gold will not peel off or flake.
There are three different ways to layer gold alloy – single clad, double clad and wire clad. Single clad has the whole 5% of gold layered on one side of the core metal. Double clad is produced by layering 2.5% of gold on each side of the base metal, making the total content 5% gold. The wire clad method layers 5% gold alloy around the entire base.
It is worth mentioning that there is a limitation in the type of jewelry that can be manufactured in gold-filled metal. Pieces are made from a sheet, tube or wire that retains separate layers of base metal and gold, meaning if the jewelry requires casting, which is melting by definition, the layers will melt into a new alloy.
Although the terms “gold-filled” and “gold-plated” are sometimes mistakenly used interchangeably, they refer to different types of jewelry.
Gold-filled jewelry contains at least 5% solid gold of the item’s total metal weight, while the content of the gold layer on gold-plated jewelry is 0.05% which is 100 times less than in gold-filled jewelry. It means the gold overlay on plated jewelry wears off much more easily, and even a small scratch on it will expose the base metal.
There is also a difference in their manufacturing processes. Gold-filled jewelry is created by mechanical bonding using heat and pressure, while gold plated jewelry is made by applying an electrical current, where the base metal is negatively charged, and the solution containing gold ions is positively charged. The attraction between positive and negative charges forms a thin layer of gold on top of the core metal.
The thickness of the gold layer also affects the jewellery’s chance of tarnishing. Both gold-filled and gold-plated jewelry may tarnish, but since the gold overlay on filled items is thicker it takes longer for that to happen. On the contrary, due to the thin layer of gold on plated items, they quickly tarnish once the gold wears off.