This is essentially just another stage of liquation and most of the remaining lead is expelled and oxidised to form liquation thorns, though some remains as lead metal.
22.
Analysis of 13th century cauldrons shows that they are made out of copper with a low level of silver and high levels of lead which would match that produced by liquation.
23.
From the mid-15th century silver began to be extracted from copper ores in massive quantities using the liquation process creating a boost to the mining and metallurgy industries of Central Europe.
24.
Agricola discusses various types of copper produced from the liquation process; one of these is caldarium or cauldron copper which contains a high level of lead and was used to make medieval cauldrons.
25.
Liquation requires that the silver-rich copper first be melted with approximately three times its weight in lead, as silver has a greater affinity with lead, most of the silver would end up within this rather than the copper.
26.
If the copper is assayed and found to contain too little silver for liquation to be financially viable ( around 0.31 % is the minimum required ) it is melted and allowed to settle so that much of the silver sinks towards the bottom.
27.
Some say this shows liquation was being carried out in the Near East as early as the second millennium BC . Crucially, however, these texts do not specifically mention lead being used with copper to produce silver, as would be expected for liquation.
28.
Some say this shows liquation was being carried out in the Near East as early as the second millennium BC . Crucially, however, these texts do not specifically mention lead being used with copper to produce silver, as would be expected for liquation.
