This process is not 100% efficient. At the Lautenthal, Altenau, and Sankt Andreasberg smelting-works in the Upper Harz between 1857 and 1860 25% of the silver, 25.1% of the lead and 9.3% of the copper was lost. Some of this is lost in slag that is not worth reusing, some is lost by what is termed ‘burning’, and some of the silver is lost to the refined copper. It is clear therefore that a constant supply of lead was needed to make up for that lost at various stages.