I’ve been extensively reading articles and posts on about fluxes and techniques to try and improve the quality of my alloy. Sawdust seems to be the consensus favorite.
One thing I haven’t seen is any warning about fluxing with sawdust or chips from tropical hardwoods or engineered wood products.
Due to the high silica content and chemicals that make them so rot resistant, the dust created from working tropical hardwoods is nasty stuff to breath in. And that’s without throwing it into a pot of molten lead.
Besides the health hazards (which is reason enough to stay away from tropicals) I have no idea how silica would behave in the melt. It would probably just form dross, but I’d rather not have it in the pot.
Just like scrap lead, don’t flux with sawdust if you’re unsure of the composition, and don’t use any from tropicals at all.
A bag of pine shavings from the feed store isn’t going to break anyone.