I swapped out the "orange thing"-70's fireplace thingy- in October. Installed the Timberline in it's place. (pre-welded all the secondary air mods. in place, in the house) and have, as of 1 hour ago , scrubbed the flue 3 times. First two inspections prior to cleaning, showed 1/4" of black fluff on the inside, no glazing or other forms of the nasty stuff. Tonight, the stove was at 100 °F when I checked/scrubbed the flue pipe. Just hot enough to have a positive up-draft. And I had a nice plume of "coffee grounds". Very little black, but alot of dark brown fluff. This is a first, so I'm wondering if this is normal at this time of year? I think my exterior pipe is retaining more heat, and less accumulation of residue from burning. Any thoughts?