Posted 05/21/2011 02:50 am
I'm guessing this has Verdigris;
Cleaning is risky business...
There are commercial cleaners like Lighthouse Environmentally Safe Coin Cleaners
Mostly a basic rinse with water would do a god job helping.
If the verdigris is light, wiping with vinegar may remove it. Follow with a water rinse.
On nasty coins its better to dip the whole coin in vinegar, only do this for a few seconds, to a few minutes depending on how much you want it cleaned. Always keep an eye on it as vinegar is strong and will take of all the tarnishing too. Cotton swab gently so you don't scratch the surface, or use a cloth that won't scratch the surface. Thoroughly rinse the coin with water to stop the vinegar corroding the surface.
Sometimes the best thing to do is use basic latex gloves when dipping in vinegar and using your fingers to gently rub the surface of the coin.
Also when the coin is cleaned its good to seal the surface of the coin with something like a soft wax product, or I guessing even something like Vaseline- petroleum jelly would stop the verdigris from growing back. Although I don't know if this would harm the coin in the long run.
I've heard other cleaning techniques but have not tried it myself...
Verdigris can be cleaned from brass and copper with a solution of ammonia and salt.
Restoration and cleaning of medals @ http://www.angelfire.com/nj/ww2/ccleaning.html suggests on copper and coppers alloys: "If the area of corrosion is not great or very deep, a bone needle may be used to loosen and remove the verdigris. Badly contaminated medals should be alternately soaked in a 20% solution of sodium sesquicarbonate and worked with the bone needle".
Cleaning is risky business...
There are commercial cleaners like Lighthouse Environmentally Safe Coin Cleaners
Mostly a basic rinse with water would do a god job helping.
If the verdigris is light, wiping with vinegar may remove it. Follow with a water rinse.
On nasty coins its better to dip the whole coin in vinegar, only do this for a few seconds, to a few minutes depending on how much you want it cleaned. Always keep an eye on it as vinegar is strong and will take of all the tarnishing too. Cotton swab gently so you don't scratch the surface, or use a cloth that won't scratch the surface. Thoroughly rinse the coin with water to stop the vinegar corroding the surface.
Sometimes the best thing to do is use basic latex gloves when dipping in vinegar and using your fingers to gently rub the surface of the coin.
Also when the coin is cleaned its good to seal the surface of the coin with something like a soft wax product, or I guessing even something like Vaseline- petroleum jelly would stop the verdigris from growing back. Although I don't know if this would harm the coin in the long run.
I've heard other cleaning techniques but have not tried it myself...
Verdigris can be cleaned from brass and copper with a solution of ammonia and salt.
Restoration and cleaning of medals @ http://www.angelfire.com/nj/ww2/ccleaning.html suggests on copper and coppers alloys: "If the area of corrosion is not great or very deep, a bone needle may be used to loosen and remove the verdigris. Badly contaminated medals should be alternately soaked in a 20% solution of sodium sesquicarbonate and worked with the bone needle".
