To make white gold, base metals like zinc, nickel, palladium and manganese are mixed with pure 24K Yellow Gold in different ratios and melted into a lower karat, off-white alloy. What we call White Gold is actually a yellowish material and it’s the Rhodium plating that makes White Gold have the nice finish that we come to expect.
There are home solutions for doing touch up Rhodium Plating, but it is highly recommended to have your plating done by a professional jeweler especially for thorough plating on beads and larger items. The home portable devices available on the market, like electro-plating pens are not practical for bulk production and work only on Karat Gold. They do not work on Sterling Silver.
If you do Rhodium plating on your own, you must take proper precautions as Rhodium solution is highly acidic and corrosive solution containing poisonous materials like Cyanide. Proper safety measures include (but are not limited to) working in a very well ventilated area and wearing safety goggles, gloves, and a protective mask, as inhaling fumes for a prolonged period can be extremely harmful to your health.
-Cyrus Nemani, Gempacked