Cleaning coins is a job for experts but since I know that you are going to try I will try and help you. In cleaning ancient copper or bronze coins I still recommend cleaning first with tap water and blue Dawn dish detergent with frequent brushing. I recommend the use of a brass bristle brush until the design is liberated from the dirt.
If you are having trouble holding your coin and brushing it place it on a piece of unfinished pine shelving. An old cutoff of any semi rough timber is great.
The coins do not seem to move much just
laying there while you brush them and you do not get sore fingers or
dirty hands. If you brush carefully you can still use the brass bristle
brush after the design is visible but great care is required and should
you find that you are getting any shiny spots (areas where the patina
is removed ) stop!
I have been unable to harm any ancient coins brushing them with a nylon bristle brush. Following each soak and brush you need to wipe each coin with a fluffy towel. You will be surprised at how much dirt comes off on the towel when you have finished brushing and rinsing. I use this process until I am happy with the results. This will vary with different coins.
Only you will know when you are finished and remember you can always come back at another time and clean a little more when you feel more comfortable with it. In cleaning coins "Patience is the ultimate coin cleaning tool".
Some times a scraping tool is employed to pick debris from around the lettering or into the verdigris to cause it to dissolve quicker. There are many available depending on your skill level from sharpened bones, brass scrapers and picks, to stainless steel needles.
I recommend the use of the tools above in the order given and move on only as your experience warrants. Remember it can take only a careless second to spoil your coin.
On cleaning coins with verdigris: you first need to have your coin clean of any wax or oil product particularly preservatives. The verdigris is a chemical reaction occurring between the moisture in air and the coins surface. This chemical reaction eats into and destroys the coins surface.
have had great success in removing verdigris from some of my prize
specimens using Benzotriazole 5% in Ethanol. (Which is flammable and
only to be used out side in open air with eye protection). It took
longer then I had expected but I am pleased with the results and I have
not damaged the patinas.
I have read that some patinas have been harmed using this product but so far that is not my experience. When your coin is clean of verdigris, anywhere from a week to some months depending on the depth of the reaction, the coin must be soaked in distilled water for at least a week but a month would be better.
Your coin is then dried in
air and then in an oven, to drive out any entrapped moisture. The oven
should only be moderate heat about 200 F or 140 C. Leave it to dry in
the moderate oven at least 10 to 15 min. remove and cool to room
temperature slowly. Apply Ren wax or Lanolin oil to the surface to seal
it from the elements.
On cleaning coins of silver. Silver coins are not plated silver but coins which are primarily silver. Silver coins with roughened surfaces from being to close to a fire or those which have acquired extra metal on the surface respond well usually to being wrapped in aluminum foil placed in a lid or shallow dish containing lemon juice or vinegar. Time is important here so do not leave your coins to soak in this manor for more then five minutes per each inspection and the desired effect is achieved.
Silver coins with hard black encrustation
sometimes respond to lemon juice in the palm of the hand and gently
rubbing the coin into it. If really stubborn I use bicarbonate soda,
(baking soda) in my palm as a paste and gently rub my coin through it
until the substance is dissolved. For some coins cloudy ammonia soaking
works wonders. If the lettering is dirty a nylon bristle brush will
make the cleaning much easier.
Also, wear eye protection as some of the cleaners splashed into the eyes will harm your eyes. All cleaning process should end with a soaking in distilled water. This will give your coin a clean surface and allow re-toneing which would make the coin more desirable to some. The absolutely key element in cleaning coins is patience.