Posted 06/03/2017 08:53 am
British .500 fine silver coins were made from quaternary metal:
50%silver, 40% copper 5%nickel, 5% zinc.
They were blanked, washed with acid (pickled), and rinsed with water before being struck into coins.
The pickling preferentially attacked the alloying metals, thus enriching the silver in the surface layer.
In order to not attack the silver, the pickling acid pH has to be rigidly controlled.
It seems that another blank was resting on this one for too long during pickling process.
It also seems that treating with Silver Dip did not get as far into the body of the coin as the pickling did.
50%silver, 40% copper 5%nickel, 5% zinc.
They were blanked, washed with acid (pickled), and rinsed with water before being struck into coins.
The pickling preferentially attacked the alloying metals, thus enriching the silver in the surface layer.
In order to not attack the silver, the pickling acid pH has to be rigidly controlled.
It seems that another blank was resting on this one for too long during pickling process.
It also seems that treating with Silver Dip did not get as far into the body of the coin as the pickling did.
