Hobbies And Interests
Preparation
Cleaning coins is a slow process requiring simple tools and a lot of patience. You'll need some cups with lids, a toothbrush, needles, toothpicks and a hobby knife for the detail work. Make sure you have a source of bright light, and a table magnifier or stereo microscope will be useful too. Finally, you'll need some distilled water, lanolin or olive oil, and possible chemical cleaners like CLR, ammonia or lye. Not all coins will clean up well. Sort them into piles by whether the coin is likely to turn out well, mediocre or unsalvageable. As you practice, start with the unlikely ones first to practice or experiment on.
Start Gently
When you begin cleaning a coin, start with gentle techniques first. Brush the coins with the toothbrush to remove loose particles, then wash with soap and water, and soak in distilled water. Don't soak coins in tap water, which can contain harmful minerals. After soaking, brush and wash the coins again and then soak in distilled water for several more days. Repeat the process until it stops having an effect. Wipe the coins and then lay them on a cookie sheet and bake them in a warm oven until they are dry.
Oil
For coins that still have packed dirt and corrosion, soak them in olive or lanolin oil. These oils have a mild acid in them that can penetrate and soften most encrusted dirt and corrosion. Fill a glass with oil and put the coins into the glass, then soak the coins for one to two weeks. Put the coins under the magnifier or stereo microscope to see details as you use a knife, toothpicks and needles to pick away the dirt. When using metal tools, be careful not to damage the details of engravings and images. Re-soak repeatedly to get all the dirt off. When clean, wipe off all oil, wash with soapy water and bake dry as before.
Chemical Cleaning
Coins that have been in extended contact with the earth can absorb minerals over time that leave discolorations on the surface of the coin. Soak the end of a toothpick in a small cup of CLR cleaner, then dab the toothpick over the spot to work it into the stain. Let it stay on the coin for a couple of minutes, then swab with distilled water to wash away loosened particles. Repeat until the stain is gone. Don't get CLR on places that are already cleaned to avoid leaving a bare spot. Wash with soap and water and soak in distilled water for 30 days, changing the water daily. Again, dry and bake to remove all moisture. Ammonia, lemon juice and lye will clean silver. Be careful with lye to avoid pitting. Wash, dry and bake to remove moisture.
Electrolysis
Electrolysis works quickly on encrustation, but it also strips the patina from coins and can cause surface pitting and permanently damage. It is not recommended.
Preservation
When your coins are cleaned you can protect their surfaces by coating them with a clear acrylic or applying a light coat of Ren-Wax. This helps prevent further corrosion on the freshly cleaned surface.