"Gold Filled" Defined
According to the United States Federal Trade Commission, gold filled jewelry refers to jewelry that "has a layer of at least 10 karat gold mechanically bonded to a base metal". Other names for this term are "gold overlay" and "rolled gold plate".
Gold filling is a process involving the bonding of gold with another base metal. Examples of these base metals are brass and nickel. Essentially, a sheet of real gold is fitted on top of a sheet of base metal, after which they are enclosed in a container and their edges are covered with paste. After the sealing process, the two sheets are exposed to an extremely high temperature and placed in a hydraulic press in order to weld the two metals together. Once the gold and the base metal are welded together, they are placed into a rolling mill and subjected to another heat treatment to further bond the materials together. The product is a material that looks like gold but is actually only around five percent gold.
Gold Filled Versus Gold and Gold Plated Jewelry
According to the Federal Trade Commission, only products that are made of fine 24 karat gold in its entirety can be given the label "gold". Therefore, if the product you are looking at is actually a gold alloy, with ten percent or more of the alloy made of gold, the product should be described as being "10 karat gold" or "14 karat gold" and so on. Meanwhile, if gold is merely electroplated or coated with gold, which must not be less than 10 karats in fineness, the product should be described as being gold plated.
Gold filled jewelry, just like gold plated jewelry, is not made from pure gold, unlike products that are designated as gold. Gold filled and gold plated products are the results of combining gold with other metals. Meanwhile, the difference between gold filled and gold plated jewelry is that gold filled jewelry is the product of gold and another base metal being welded together, while gold plated jewelry is the product of gold being plated or coated onto another metal.