Cleaning Roman and Ancient Coins
After buying or finding ancient coins they generally need cleaning. More often than not they have a thick encrustation on them from being buried for thousands of years. On first look they can appear to be completely featureless in many cases. In general terms those that you can see at least some detail on will tend to clean up quite well. Whilst those that have no identifiable marks on normally carry about a 60% success rate. It really does depend on a number of factors as to exactly how many will clean up successfully. Firstly ensure that you get the best unclean coins you can to start with. A lot of sellers of these coins sell the very worst quality smallest coins to the public on ebay and some other sites. Never be drawn into buying from anyone that advertises “Gold found” or sells counted lots unless you are buying premium unclean coins. The fact is if they have been counted they are generally small low quality budget coins that have been extensively sorted. Another popular trick when selling coins is to sell “unopened bags”. Basically all you do here is end up buying bulk lots of the very smallest lowest quality unclean coins so beware!. We only sell by weight and you can select the Hoard that you would like to purchase from so you get some choice with absolutely nothing taken out.
Steps to clean your Ancient coins
Firstly it is important to go through them all and sort them out by visible condition. We would normally suggest three lots. Firstly those showing good detail, those with some detail, and those with no detail. Remember to be patient, the aim here is to preserve the patina and remove the dirt if possible.
Place them all in plastic containers with lids and put some masking tape or a sticker on the front of them with the date and other details on such as how they have been sorted.
The first 24 hours
Then I would suggest using Distilled Water for the first 24 Hours on all of them. Now a note here is proper distilled water is not the same as tap water. I’m no chemist but distilled water works great and tap water does nothing!. Simply boiling tap water does not make it distilled either so either purchase some off the internet or maybe at the supermarket. It can quite often be found to use in household irons to stop them leaving steam marks on clothes. After 24 hours have a look at them and some coins might well be showing really good detail especially from the container that had the best ones put in. I would suggest rubbing them all with a tooth brush then returning the ones that need longer to the distilled water.
The next 7 Days
I would now suggest giving them longer and longer periods in the distilled water. After about a week go through them all and using the brush again and see how they are all coming up. At this point I would suggest drying them all off and re categorising them all into the good, average and worst coins again as the approach is likely to be different for the different lots from here onwards.
After 7 Days
Use olive Oil now instead of the distilled water in the best lot of the three. Try not to use Extra Virgin olive oil just the normal stuff as it seems to give better results. In this first lot with the best coins in just use Olive Oil with nothing else added. In the second lot use Olive Oil with around half a tea spoon of Lemon Juice. And in the worst lot I tend to double the amount of lemon juice to about a teaspoon full. Try and add the Lemon Juice to the Olive Oil then give it a good stir before you add the coins to ensure that it is evenly spread around. I would check all three lots weekly for the next three weeks and see how they are coming on. The olive Oil will go green and thick with muck. When it does this it means that it is time to change the solution. At the same time clean the coins off again using a Tooth Brush and distilled water then return them into the new Oil.
After a Month
You should have started to see some really good results by now unless you have some seriously encrusted coins or featureless slugs in there. Clean all coins with a brush and distilled water again. At this stage you can probably pick dirt and encrustations off them with either a wooden tooth pick or dental instruments. An illuminated magnifying glass will be good to have at this stage as it will help you not to damage the coins. You now have a couple of options, you can either repeat the process that you have been doing for the last month for anything up to a year, or try something a bit more radical.
Personally I will normally try something a bit more radical on the unclean Roman coins that show no signs at this point of cleaning up. Some of the best coins I have ever cleaned have been the very worst lumps when I started so it can pay to try something a little more radical.
The Hot Pot
When you have decided you are willing to try something a little more radical for cleaning the worst of your Ancient coins try this. Use a Saucepan heat up some Olive Oil and lemon Juice in it. By this point I would probably recommend using about 5- 10 tea spoons of Lemon Juice to make a greater concentration. Stir it all together then put the coins in. Bring it to the boil and then simmer. Generally I normally simmer whilst stirring with a wooden spoon for about half an hour or until the solution turns into a completely green mess. Rinse all the coins then under the tap then give them a finishing scrub with a tooth brush and Distilled water. You can repeat this as often as you like or until the solution stops getting dirty. I would suggest you use it to get the worst off then return the coins to a longer more gentle soak in Olive Oil or Distilled water.
This can be an effective method for removing time scale and very thick encrustations if done with a good machine. This can damage the Patina on the coins or even the coins in some circumstances so only use it as a last resort.
You can quickly clean your Ancient Roman coins using electrolysis; typically you can take a crusty and zap it clean in around 15-30 minutes. But once again it can damage the patina or the surface of the coin. That being said if it is a crusty that will never clean up using a conventional method then maybe it is the way to go. There are a number of sites on the internet that will show you how to build a simple electrolysis tank that will cost next to nothing to use.