Hi Hal,
It is my opinion that fluxing pure lead achieves no real purpose. When lead is exposed to the air, it, like most metals, oxidizes due to binding with the oxygen in the air. Heat accelerates this process. So molten lead will readily oxidize with the exposed surface of the melt being exposed to air.
Placing a barrier on top of the melt (a layer of charcoal, or sawdust (which quickly turns into charcoal), or anything else which prevents the lead from being exposed to the air, will help reduce oxidation. I've actually been meaning to make a little "lid" to set on top of my Lee-420 melt surface (steel will float on the lead) with a notch to clear the valve stem. Obviously this will not work if ladle pouring. Even "fluxing" with beeswax will leave an oily film for some seconds which can appear to leave a nice shiny melt surface. But this burns away in a minute or so and now in addition to lead oxide you have burned organic material floating on top of your melt.
I believe it is in the US Ordnance manuals where they describe how to reclaim dross. Basically you heat it in a furnace with charcoal to very high temperatures (probably glowing - way higher than casting temperatures). When heated to this temperature, the oxygen/lead bond is broken and the oxygen is free to fly away. By having carbon in the mix, the free oxygen would rather bond with the carbon than the lead, making CO and CO2, leaving pure lead behind.
I don't think the chemical reaction to reduce lead oxide back to lead can be achieved at melting temperatures.
Steve
Steve Sheldon
Commander
4th Louisiana Delta Rifles
NRA Certified Muzzleloading Instructor
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