What exactly is gold filled wire?
Gold-filled, or gold overlay, is made by heat- and pressure-bonding a thin layer of karat gold to a brass (or other base metal) core. The "14/20" or "12/10" 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.