Before jewelry arrives in stores to be purchased, it usually has a metal coating placed on it. This serves several purposes. First, the coating gives the jewelry a richer, smoother color. Another reason is that the coating hides bumps in the jewelry. The process of placing this metal layer onto the jewelry is called electroplating.
A Little Introduction
You might already know that atoms are very small-so small that you can't see them. To give jewelry a nicer look, engineers put jewelry in a small bath filled with millions of gold atoms. Inside the bath are three small pieces called cells. The gold atoms either float in the bath or are stuck to two of the cells that grab the gold atoms. These cells are called anodes.
The jewelry that is to be polished is placed at the third cell, which is called the cathode. Then, just like a current of water, the atoms at the anode all head toward the cathode, where the jewelry is placed. We say that, when this current is on, the gold atoms are "attracted" to the cathode. If the engineer waits long enough, the entire piece of jewelry will have a new coating of gold on it. This is a lot like how electricity works!
If you want to find out more about electroplating jewelry, you can talk to a chemical engineer or an electrical engineer.
Much of the information on this page was taken from an article written for Gold Technology (no. 35, Summer 2002) by Dr. Christopher Corti.