As others have stated, you shouldn't have any issues as long as the lead is clean when you put it into your bottom drop furnace.
While I have not messed with lead much, I use to work in a machine shop that would repair/recast babbitt bearing. Babbitt is very similar to lead but without the hazards. We used a good sized furnace to melt the babbitt and keep it at the correct temps for pouring. We used potatoes on a long steel rod to stir the babbitt to get impurities to float to the top and then we would skim it.
Most of the bearings we worked on were for electric power plants. The biggest bearing we did were from the Harry S Truman damn in Missouri. Those had an internal bore diameter around 109 inches. A 2 foot diameter bearing was considered small for us.
While I have not messed with lead much, I use to work in a machine shop that would repair/recast babbitt bearing. Babbitt is very similar to lead but without the hazards. We used a good sized furnace to melt the babbitt and keep it at the correct temps for pouring. We used potatoes on a long steel rod to stir the babbitt to get impurities to float to the top and then we would skim it.
Most of the bearings we worked on were for electric power plants. The biggest bearing we did were from the Harry S Truman damn in Missouri. Those had an internal bore diameter around 109 inches. A 2 foot diameter bearing was considered small for us.