Response from another thread but thought it would be worth adding to this thread as well.....
No problem..... The trick I mentioned to Fixxah was for boolit casting (not smelting) when using a bottom drop pot..... When the pot is loaded, at temperature and I have skimmed the dross I sprinkle a small amount of boric acid (using an old salt shaker) on the top of the melt.... The boric acid fuses into a thin layer which seals the top of the melt, prevents further oxidation and helps maintain temperature... This also helps keep your alloy consistent since the tin in the alloy is usually the first to oxidize out....
When you want to restock the pot, push the protective layer to the side and refill... Then add more boric acid to reseal the melt...
BTW, when smelting I use candle wax to flux.... I try and get the clips and unmelted WW (Zinc, Aluminum and steel) out as soon as possible and then quickly flux with a marble sized piece of wax.... As soon as it catches I stir well into the melt being sure to scrape the sides and bottom... Remove everything that floats up and then repeat with more flux.... This continues until nothing much comes up and then I fill my smelting molds... Really important to get these small impurities out (looks like coarse ground pepper) as it will impact your boolit mold fill as well as contribute to "leaky pot syndrome" when some of it gets into your drop mechanism... I usually use at least 4 smelting molds so that the first filled have a chance to solidify by the time I've filled the 4th.... Then it's dump and fill for each mold up the line... I am currently using a set of molds that are tig welded out of angle iron but have muffin tins (non stick coated) as well....
Have found that small ingots or ingots that are long that you set vertically in your casting pot work best best for me so that there is minimal drop in temperature when I restock the pot so if you go the muffin tin route get the one for the smaller muffins.... That way you can often continue casting when you do small adds which really helps keep things moving and the boolit mold at temperature... For those of you that cast you know that happiness (and good boolit drop) is a boolit mold at the right temperature....