I am presently, personally anointing myself as a bona fide intermediate coal burner. My current burn is now (knock wood er...coal or whatever) 32 days. I nursed it through two near death experiences. I think I finally have a good handle on what I am doing. SO... now onto fine tuning and more advanced topics. I notice that when I shake the grates I get a variety of shapes sizes and colors in my ash. Fine fly ash in shades of gray , brown and rust; large flat pieces resembling small pieces of slate or shale also in the same color schemes ; brittle striated chunks of burnt coal; and finally, small gray to black molten looking chunks of .... I don't know. Is this variety normal? Does it matter?
I have a newmac combination furnace