Was reading Glen Fryxell's great, free, downloadable pdf, book on lead bullets. In the section concerning casting fluxes, he discussed the advantages of saw dust as flux, explained the chemistry behind the recommendation, and said he liked walnut sawdust for a few reasons, including good smelling smoke.
I have been working on a bulk bag of walnut shell media forever, used with a tiny amount of oil to eliminate dust. Marvel Mystery seems to work well but I don't imagine that is critical.
Assuming I have adequate ventilation to deal with whatever might be in my various sources of alloys and scrap lead, would there be any reason not to recycle / dispose of the dirty media as a casting, or more probably, smelting flux?
Essay W