We get this question a lot and we wanted to share with you that gold-filled materials are an excellent alternative to solid gold, offering gold's characteristic warm yellow or blushing rose tones at a fraction of the cost. At the same time, gold-filled is more durable and retains more value than gold-plated pieces.
Despite how it sounds, gold-filled metal is not actually filled with gold. "Gold-filled" is simply an age-old term that became accepted in the jewelry industry. Today, gold-filled is a quality designation that's regulated by the Federal Trade Commission. To merit a "GF" stamp, the material must have a layer of gold that is at least 10-karat mechanically applied to a base metal; the karat gold layer must also be at least 1/20 (5%) of the item's total weight. All of Rio's gold-filled products have a 12-karat or a 14-karat gold layer and meet the federal quality standards established by the FTC.
Gold-filled is made by heat- and pressure-bonding a thin layer of karat gold to a brass (or other base metal) core. The value of gold-filled is greater than gold-plated because gold-filled has an actual layer of karat gold, not just a microscopic film, as is the case with gold-plated items. The karat gold covering also significantly increases the tarnish resistance of the base metal substrate. Please note that gold-filled materials cannot be cast, and gold-filled casting grain does not exist.
The "14/20" or "12/20" notation refers to the industry shorthand describing the resulting material. The first number is the karat purity of the gold used; the second number is the amount, by weight, of gold to the substrate material. "14/20" gold-filled material is made with 14-karat gold, and the gold represents 1/20th (or 5%) of the total weight of the material. You may occasionally see other notations, too; each will inform you about the material's make-up.
Pretty cool, right?!