Cleaning tips

I am not, by any means, an expert on the cleaning and conservation of coins, but these are some methods that I have used with good results. Use these techniques only as a guide, and keep in mind, if you have a coin that looks like it might be a truly valuable one, don't clean it. Let an professional do it. They have the training and tools to do the job right. As you gain experience, you will find that your coins will look better all the time, but while you are learning, you will ruin some coins.

In other words, do your practicing on less valuable coins before you tackle that beautiful sestertius of Nero ; )

-Glass or plastic cups with lids
-Toothbrush
-Distilled water
-Straight pins, needles
-Sharpened bamboo or toothpicks for the details
-A good source of light (a gooseneck lamp works great)
-A table magnifier
-Hobby knives with replacement blades
-Olive or lanolin oil

If your budget allows, the best investment you can make is a stereo microscope. Using one can make cleaning the most stubborn coin into a joy. If you spend some time looking around, you should be able to find one for around $150 or so.

As you gain experience, you will find other tools that work well for cleaning. Don't be afraid to experiment, but make sure that you use coins that you can afford to ruin when trying new techniques, because you are going to destroy a few of them.

The idea behind cleaning coins is to bring out the details, and to make the coin as attractive as possible, and some (maybe many) ancient coins are beyond salvation. They are just too far lost to the process of corrosion to even bother trying. I usually sort the lots I buy into several piles: 1) Likely to turn out nice; 2) May turn out nice; 3) Unlikely to turn out nice; 4) Horrible...just horrible.

(The last coins go into a big plastic bag, and I use those to try all sorts of horrible experiments on :)

Always choose the most gentle methods first: Brushing, washing and soaking first, followed by mechanical cleaning, followed by chemicals.

Use local techniques over global techniques (ie: treat only the areas of the coin that need cleaning, rather than the entire coin.

As with a great work of art, the most important thing to know is when to STOP!

Ok....you bought a lot of coins, and you are ready to get started. Begin by soaking the coins in distilled water. Don't use tap water, which can contain dissolved minerals. Soak the coins overnight, and then take them out and brush them lightly with your toothbrush (Well, not YOUR toothbrush. Use an old one). Return them to the water, and let them soak for another day or two. Remove them again, and give them another light brushing. Repeat this over several weeks. You will find that many of the coins with just a light coating of dirt will respond well to this method of cleaning. After a couple of weeks, some of the coins will be clean enough to be identified. Dry them off, and then bake them in a warm (200 degree) oven for at least one hour to evaporate any water left after drying. Moisture is the enemy of coins!

Coins that still have hard packed dirt can be soaked in olive or lanolin oil. The oil, which contains a very mild acid, will penetrate and soften all but the hardest encrustation. Put the coins in a glass or plastic container, put the lid on it, and place it somewhere that it won't be knocked over. Spilled oil is not a way to maintain domestic tranquility. Trust me on this. I know. Allow the coins to soak for a week or two. Remove them from the oil, and using your magnifier or microscope, carefully pick at the dirt. The idea is to clean the coin a small area at a time. Look for small ridges that you can get your tools under, and gently lift the dirt off. Use your bamboo or toothpicks to clean around the legends, and carefully use the needles to clean the dirt out of the small details. (This is where it really helps to have a microscope). At this time, you should be able to remove much of the dirt and encrustations. If needed, return the coins to the oil to soak for a longer period of time. This method works well, but it can be very slow. I have soaked coins for over 6 months before I have obtained the results that I want.

When the coin is cleaned to your satisfaction, you can remove the remaining traces of oil by placing it in a small glass jar with non-detergent dish soap mixed with distilled water. Carefully swirl it around, then dump out the soapy water. Repeat this several times, dry off the coin, and bake it as described while chanting the mantra:

This may not help, but it sure can't hurt.

Some of your coins may have a hard green deposit on them. This is a result of long-term contact with the minerals in the earth. I've found that a good way to remove these spots is by using CLR, which is available in most hardware stores. I pour a small amount into a container, and then place the end of a toothpick into the liquid. I allow a few minutes for the CLR to soak into toothpick, and then I carefully dab it directly onto the affected area. I let it stay on the coin for a minute or two, and then I remove it by brushing with distilled water. This will partially dissolve the encrustation, and make it easier to remove. You may find that you will have to repeat this step several times before you are able to remove all the green spots. Try to avoid getting the CLR on the areas of the coin that have already been cleaned, as the CLR will strip off the patina, leaving you with bare, shiny spots.

If you do use this method, you will have to make sure that all traces of CLR are removed from the coin. To do this, soak the coin in distilled water for at least one month, with daily water changes. After soaking, remember to dry the coin in a warm oven.

After you have cleaned your coins, if you choose, you can preserve them for storage by giving them a light coating of Ren-Wax or a clear acrylic finish. Follow the label directions for using these products.

Mention "electrolysis" when speaking to collectors, and some will just turn away and brand you a pariah for life. Others will instantly attack with intent to maim.

It will remove the hardest encrustations quickly, but it will also strip off the patina, leaving you with a shiny disk of metal. It can also cause pitting on the surface of the coin. I've used it a few times with various results, but generally speaking I don't recommend it. Controlling the chemical reaction that take place during the process is difficult. I won't describe the process here, but if you really want to try it, you can find instructions on any number of sites.

Above all, remember that the best tool to use when cleaning your coins is patience. The coins have been dirty for hundreds of years. A few more weeks won't make a difference.