I'm in the mood to experiment with alternative fluxes. In the past I've used materials from coffee grounds, to grease, to a bead of bullet lube.
I mostly cast pistol bullets using a bottom pour pot, but am starting to cast more for rifles... Working with some new molds, many of the bullets I produced have what appear to be gray inclusions. When using graphite tumbled hard lead shot for arsenic content, I've also noticed what I suspect are graphite inclusions originating from the graphitec surface of the shot, even after fluxing (since graphite should easily float to the top, if it is graphite, there must be some serious wetting holding it in the lead). I'm suspecting I'm not sufficiently fluxing my lead, or the flux I'm using is not doing a good enough job. While my pistol bullets have always shot more accurately than I have, I'd like a better standard for rifle bullets -- since I can shoot them much more accurately than pistol bullets and will be pushing them harder, I am more concerned for their uniform quality.
Also, most of my improvised fluxing materials are smoky as heck (burning coffee grounds also stink).
Since I've read that boric acid based fluxes are smokeless and form a layer of glass on top of a pot of lead, and I've got plenty laying around, I've thought of playing with boric acid based fluxes.
Any suggestions for diagnosing my inclusions, improving my technique, formulating a boric acid containing flux, cautions, or hazards for same?
Thanks in advance for your contributions.