Gold filled
Gold filled refers to a process in which an outer layer of real (= solid) gold is connected to a metal core made of brass , copper (previously also silver ). The gold is rolled on in a special process and permanently bonded to the carrier metal at welding temperature.
In the USA, where the process is mainly used, quality control is subject to the Federal Trade Commission , which among other things acts as a consumer protection authority. Only pieces of jewelery which have a share of at least 5% of the 14 or 12 carat or 10% of the 10 carat gold of the total weight may be sold as "gold filled". "Gold filled" is the legally required designation for the material. 14k (corresponds to gold 585) “gold filled”, the most common variant, is often marked with 14/20, the addition “GF” is also possible, but not required by law. 12k (corresponds to gold 500) and 10k (corresponds to gold 417) gold filled are also offered. Jewelery made from “gold filled” can also have a producer's stamp. The carrier metal for "gold filled" must comply with European legislation so that it can be sold in Germany, therefore it only contains metals that are also used as expansion metals for fine gold to produce gold alloys.
The above regulation relates to the amount of gold alloy prescribed in the weight ratio that must be used for the production of "gold filled". There is no regulation that prescribes a certain thickness of the gold layer. According to mathematical calculations, the gold layer of “gold filled” products is thicker on objects with a compact surface (e.g. spheres) than on objects with a complex surface structure (e.g. squiggles).
Gold filled, which is manufactured according to the patented manufacturing process and marked accordingly, as a classic bimetal, fulfills the respective physical and chemical properties of its two alloy metals. Empirical values confirm a corresponding skin tolerance. Due to its properties as a bimetal, gold filled, unlike galvanically gold-plated metals, can be soldered to connect individual parts. The amount of wear on the outer gold layer through use and care also corresponds to that of solid gold jewelry.
Since gold filled partly consists of solid gold, it can also be recycled, the separation of the gold layer from the carrier metal can be done in a refinery .