Steps that I take to clean ancient roman coins
I have been cleaning roman and provincial coins since March of 2004.
It has been a long process of reading countless posts and experimenting
with various chemicals and methods. There are many other methods that can be used to clean
coins, but this is the method that works best for me.
Step 1 - Buy Decent Quality Coins
When I say the first step is to buy decent quality coins I mean, that I usually buy coins that
are around $2.00 each. I am not too concerned if they show details before cleaning,
but they should at least be round and more or less weigh what they are suppose to.
The real low grade $0.60 coins are almost never worth it because they are usually degraded little
slivers of metal not worth fooling with. The only lot that I ever bought where I was ripped off
was when I bought 40 English uncleans for $0.40 each on EBay. I have read about and seen countless
other cheap lots that I didn't buy because they looked like crap. Because the cleaning process
takes such a long time, there is nothing wrong with paying a little more up front and getting
something that can be added to your collection once the cleaning is done.
Step 2 - Take pictures of the coins on arrival
After receiving the coins I break them into lots of 10 and take "before" pictures. I picked 10 coins per lot because 10 coins is about the most coins that I can fool with in one sitting, whether it be washing, or picking, or photographing them. After doing about the same thing 10 times in a row, I am ready to do something else.
After the coins have been broken into lots, I always take a before picture of the lot before I do anything else. The reason for taking the photos is threefold. First, someday I'm going to publish this good cleaning data to the web to share with the world the hobby of cleaning Roman Coins. Second, I use the photos to assign numbers to the coins for any subsequent notes that I might make about a coin. Often, I will start trying to attribute coins when I get them in. If there are any unusual coins in the lot, I like to make a note because the attribution process could be long and arduous. Thirdly, I like a before picture so that I can see how the cleaning of the coin is coming. Typically, it takes in the neighborhood of 18 months to clean a coin. This is a long time, and it is fun just to go back a see what the coin looked like when I started. Also, there have been occasions when cleaning that I hit brass, and it is with great relief to look at the original photo and see that the coin was already marred when I got it.
Step 3 - Initial wash with soap and water
I usually wash the coins off with soap and water. I use Dawn soap, because I read that Dawn had extra ingredients for grease, I don't know if this is true or just marketing hype. I use a denture brush that I bought from Walgreen's to scrub them. The denture brush is a nylon brush that is just a little stiffer than a toothbrush, but not very stiff. This initial wash doesn't take very long, it is really to just get off any loose dirt that is on the coin, and to prepare them for the initial soak.
Step 4 - Initial soak in Gringotts #1 or #2
After the initial wash, I will usually put the coins into either Gringotts #1 or #2 for a couple of weeks to soak and to start removing the organic debris. I am pretty sure that Gringotts #1 is Sodium Carbonate and that #2 is Sodium Carbonate with TSP. At any rate, they both seem to be pretty effective at removing "dirt". Gringotts #2 is stronger than #1, but they are similar enough that whatever I have on hand is what I use for the initial soak. The initial soak lasts anywhere from a week to a couple of months. This wide variation is because of my chaotic schedule, if not much is going on, the coins get a short soak, if I'm real busy or preoccupied with something else, the coins get a long soak.
Step 5 - Brushing and picking on the coins
After the initial soak the initial picking begins. I have a wide variety of tools that I use to pick at the coins, but the order that I do this is almost always the same. First I try brushing the coin off with a soft brash brush. I don't use the brash brush to go all the way down to the patina though. I use it just enough to get the harder dirt off and when I start to see the profile or legend coming up, I switch to the nylon brush, or to the nylon brush Dremel attachment.
After brushing the coin off, I start to pick on it under 10x power with my binocular microscope. I use a number of picking instruments. I have pin vises for tungsten and brass pins. The trick to using the pins is to keep them very sharp. I use both a whetstone and the Dremel sharpening wheel to keep them as sharp as possible. I have been know to use brass safety pins in a pin vise also, though the problem with using safety pins is that they become dull quickly and they often have a steel core so that when they are sharpened, the steel is exposed and caution must be used or you will punch through the patina.
I have a couple of diamond-dusted dental picks that I use for any real hard/large lime encrustations, though I don't use these as much anymore because it is difficult to use them without punching through the patina to bronze. Instead of the diamond-dusted dental picks, I have started using diamond-dusted dental drill bits that are made in Switzerland. I learned about these tools from Joe Engebretson at UAC, and they are a great improvement over the diamond-dusted dental picks. The grit used on them is finer, and they fit in a pin vise so they are a little easier to manipulate. After picking on a coin for awhile, I make a decision if more picking will do any good or not. If the answer is yes, I continue picking. When the coin gets dirty with picking debris I use the nylon Dremel brush to get rid of the picking debris. However, if picking is no longer making the coin cleaner, it is time to do the extended soak.
Step 6 - The extended soak
It is at this point that experience comes in. Should the coin be soaked in water, Gringotts #1 or #2 or in Olive Oil? Here is how I decide:
If the coin is pretty clean with just a little dirt just still adhered to the coin, I put it into either Gringotts #1 or distilled water. I usually plan on taking another look at the coin within a month or two on these easy coins.
If the coins are covered in thick clay and/or organic material, I usually soak them in either Gringotts #2, and if not so thick in Gringotts #1 for an extended time, usually 6 months or more. I throw the coins into a ½ pint jar and store them away, for sometime in the future when I can get back to them.
If the coins have the white encrustation that looks like lime rock, I drop the coin into Olive Oil for an extended soak of 6 months to a year or more. In my experience the only thing that will react to the lime encrustations is Olive Oil. Olive Oil does have the drawback that it will weaken some patinas after a moderately long soak (more than one or two months). I have read that mineral oil could be used also for this purpose, but I haven't tried it yet. After a coin has soaked in Olive Oil for an extended time and I think it is time to pick on it again, I will remove it from the Olive Oil and give it a quick boil in water mixed with detergent (I use Gringotts #1), and then let it soak in the Gringotts #1 for a week or so, before I start picking on it again. This is the easiest and least messy way that I have found to get rid of the olive oil after a soak.
Step 7 - Repeat steps 5 and 6 until you are pleased
I repeat the picking/soaking procedure until the coin is real close to being done, or at least ready for finishing.
Step 8 - Finishing
If the coin is clean and has no roughness or remaining lime stone flakes I move on to the waxing step, if on the other hand, the coin needs just a little more work, I will polish it using a 3M radial brush attached to the Dremel. These are fine nylon brushes that have diamond grit mixed into them. I have found that using the brushed labeled #2 will probably not damage most patinas. This is still somewhat experimental, but so far I have found that they work real well with doing the final clean on later roman bronzes. Until you have experimented with them a great deal, I do not advise that they be used on valuable coins. Another thing that I use is the silver brush, to add just a little sheen to the now cleaned coin.
Step 9 - Drying and waxing
Finally, to finish the coin off, I put them in an oven at the temperature of 175 (79°C) for about ½ hour. I figure this will remove any remaining water in the coin. After the coin has baked and while it is still warm I apply Renaissance Wax to it and then buff it with the nylon cup brush that fits on the Dremel. I have also used cotton and felt cloths but I honestly can't tell any difference between buffing with the nylon brush and the polishing cloths.
Step 10 - Flip 'em
Finally, I take another photo of the coin and perform my final attribution and appraisal at this time. I print up flips using Moneta, though I continue to work on my own program to database and print flips.
This list isn't extensive; it is just where I found the various supplies that I use.
a) Diamond-Dusted dental picks - Noble Roman Coins
b) Pin Vises and pins, and most Dremel attachments - Common Bronze
c) 3M Radial brushes - Progress Tool
d) Silver brush - Nemesis
e) Brass and Nylon Hand brushes, and other tools - Common Bronze
f) Renaissance Wax - I got mine from Dirty Old Coins, but other vendors including Common Bronze now sell it.
g) Gringotts is available at: Common Bronze and Noble Roman Coins
Learning to clean coins has been a long process of reading countless posts. But the posts and conversations with the following people have been especially helpful: Tony Jaworski, Joe Engebretson, Leisa Waggoner, Ernest Miner, Bill and Holly Roth, Mark Lehman, Susan Headley, and Kevin Sandes