Thursday 2 August 2012
The production of silver was not without its challenges. Pliny describes all silver smelting using the ancient process of cupellation (used since the early Bronze Age) where lead ore containing silver - usually Galena - was smelted at temperatures in excess of 900 degrees Celsius to oxidise the lead and retrieve the pure silver metal. Using this process the Romans were able to produce silver from low grade ores containing as little as 0.01 percent of the precious metal and the same techniques continue to be used for modern processing. However all that oxidising metal brought with it the same issues of pollution lead smelting has today. Hundred of tonnes of charcoal would have been needed to supply the mines each week - much of Spain's and Britain's forests went into the furnaces, and the fumes produced from the cupels (the smelting vessels) was described by Pliny as being "harmful to all animals, but especially dogs" - although I imagine the slaves working the smelter didn't fair too well either. In fact, as far as the bounds of slavery went in the Roman world, being sent to the silver mines was considered the worst possible scenario...and was often in lieu of a death sentence. Needless to say, when it came to making money in those days, there was always someone who had to do it the hard way.
Find out if Calvus ever made any money