Traditional sterling silver is an alloy of 92.5% fine silver, and 7.5% copper. The copper content of the sterling silver is what causes sterling silver jewelry to tarnish over time.
14K Gold Filled
14K gold filled wire has a layer of 14k gold bonded to a brass core. 1/20th of the overall makeup is 14k gold. The layer of gold in gold filled products is much thicker than a gold plating. Gold plate wears off in just a few months, whereas gold filled will last decades. Gold filled jewelry will not tarnish over time.
Silver fill wire made by bonding a layer of sterling silver (.925) to a brass core. The thickness of this sterling silver layer constitutes 1/10 of the overall weight. This layer is much thicker than a silver plating - making this product last decades, rather than months. The price of silver has climbed along with the price of gold, making this a fabulous alternative to those who love sterling silver but are cringing at the high price. Silver filled jewelry will tarnish over time in a similar manner to sterling silver jewelry.
Copper is a pure unalloyed metal, considered a base, or non precious metal. Copper can tarnish fairly quickly, going from a bright red-orange to a dark caramel brown. Copper is also very easily cleaned -- a dunk in vinegar, or ketchup for a few minutes will remove any tarnish.