To oxidize metal, first put two eggs in water, and boil for 10 minutes. Use dish soap to wash the metal, and then fully dry it. Drop the boiled eggs into a Ziploc bag, and crush them as small as possible; this releases sulfur. Place the metal in the crushed eggs, and seal the bag, making sure the metal is as immersed as possible before tightly closing the bag.
Check the color of the metal in 15 minutes without opening the bag. It should be darkened. Leave the metal immersed in eggs, checking frequently, until the desired color is reached. Then, take the metal from the bag, and remove the egg with soap and water.
Silver black is another method to oxidize metal. This solution has hydrochloric acid, so take caution while applying it to metal. Ensure proper ventilation, and protect the working surface with rags. Use a fine brush to apply the silver black to the metal. If a darker finish is desired, repeat the application. Use water to rinse the metal once the correct color is achieved.
Liver of sulphur can also oxidize metal and is available in both solid and liquid forms. When using the solid form, it must first be dissolved in water. If using the liquid, place a capful of oil into hot tap water, and agitate. Insert the metal into the solution, and wait until the desired color is reached. Remove the metal using rubber gloves, and rinse.