coin conservation from museum website

Elem21wed

I found this on the website of the Government Museum of Chennai India. I'm just putting this out there. I am going to personally try these methods on some "carbon spotted" and "milk stained" coins and see what happens. I will post in a few weeks the results.

Conservation of Silver Objects / Coins

Silver is a noble metal, which turns black (silver sulphide) and white (silver chloride).

Silver objects / coins are cleaned by keeping them in a 10% solution of formic acid to remove the black colour (silver sulphide) and immersed in a solution of 10% ammonia to remove the white colour (silver chloride). After thorough washing, the coins are dried and coated with a 2% solution of poly vinyl acetate in acetone as a preservative coating.


link to text with photos


I will post in a few weeks the results.


Christopher

options26

Interesting article. Please post both before and after pics, thanks.

AUandAG

I'll be watching for your results.

good luck,
bob

ModernCrapNut

This section was interesting too. I guess no one has yet figured out a good method.


Coins were made out of the coinage metals such as gold, silver, copper and their alloys like electrum, bronze, brass. They were kept buried under soil and stored in copper vessels. Now, they are received as treasure-trove finds. Due to corrosion of the vessel as well as coins, the coins are found stuck together appearing bluish green.

These coins are cleaned with an alkaline solution of Rochelle salt (15 gms of Rochelle salt +5 gms of sodium hydroxide+80 gms of water). The corrosion products are removed and the copper coins appear red. The red cupric oxide corrosion is removed by soaking the coins in 10% citric acid, washed well to remove the salts, dried and a preservative coating of 2% poly vinyl acetate in acetone is provided. By this method the aesthetic look of the objects are lost.