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Gold-filled jewelry is composed of a solid layer of gold, which must constitute at least 5% of the item's total weight, mechanically bonded to sterling silver or a base metal. The related terms "rolled gold plate" and "gold overlay" may be used if the layer of gold constitutes less than 5% of the item's weight.〔(【引用サイトリンク】url=http://www.jvclegal.org/JVCsupplement.pdf )〕 Some high quality gold-filled pieces have the same appearance as 14 karat (58%) gold. Gold-filled items, even with daily wear, can last five to 30 years but will eventually wear through. Gold-filled items are 50 to 100,000 times thicker than regular gold plating, and 17 to 25,000 times thicker than heavy gold electroplate (sometimes stamped HGE or HGP—usually found on cubic zirconia "cocktail rings"). ==Definition== In the United States, the quality of gold-filled is defined by the Federal Trade Commission (FTC). If the gold layer is 10 kt fineness, the minimum layer of karat gold in an item stamped GF must equal at least 1/10 the weight of the total item. If the gold layer is 12 kt or higher, the minimum layer of karat gold in an item stamped GF must equal at least 1/20 the weight of the total item. The most common stamps found on gold-filled jewelry are 1/20 12kt GF and 1/20 14kt GF. Also common is 1/10 10kt. Some products are made using sterling silver as the base, although this more expensive version is not common today. These standards are for modern gold-filled items. It is not uncommon to see 1/8 14kt gold-filled marks, plus many other variations, on items from the 1930s, 1940s, etc., which would have to be marked "Rolled Gold Plate". The FTC allows the use of "rolled gold plate," "R.G.P" or "gold overlay" on items with lower thicknesses of gold than are required for "gold-filled."〔 "Double clad" gold-filled sheet is produced with 1/2 the thickness of gold on each side. 1/20 14Kt double clad gold-filled has a layer on each side of 1/40th 14Kt making the total content of gold 1/20. The thinner layer on each side does not wear as well as single clad gold-filled. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gold-filled jewelry」の詳細全文を読む スポンサード リンク
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