A gold fill is a jewelry material made by mechanically bonding a solid layer of gold to a base metal core – most often brass or copper – using heat and pressure. By U.S. FTC regulation, the gold layer must constitute at least 1/20th (5%) of the item's total weight. That bonded layer is 50 to 100 times thicker than standard gold plating, which is why gold-fill pieces hold up to years of daily wear.
Gold fill is commonly stamped 1/20 14K GF or 14KGF on clasps and findings. It appears throughout chains, bracelets, earrings, and pendants as a durable, lower-cost alternative to solid gold. The gold layer gives a genuine warm gold appearance that does not flake or wash off the way plating does under normal conditions.
When it comes to repair, gold fill behaves differently from solid gold. Soldering requires lower heat to avoid damaging or discoloring the bonded gold layer. Ring sizing on gold-fill bands is possible but limited by how much the metal can be manipulated before the layer is compromised. If the gold layer does wear through at high-contact points, re-plating can restore the appearance without replacing the piece.