Bonfield: reading the three stages of creosote in a farmhouse flue

By Jacob Dove, Friendship Chimney Sweep

What we found

A farmhouse a mile out of Bonfield, wood stove in the kitchen, flue running up an exterior chimney on the north wall. Sweeping it in October, we found stage one flaky soot near the top where the flue had been open to the wind, stage two crunchy tar through the middle, and a band of stage three glaze just above the stove connection where the cold exterior chimney met the smokiest exhaust. Three stages in one flue, and each told us something.

What the stages mean

Stage one, the dry flakes, comes from hot fires and dry wood; it brushes off easily and is the goal. Stage two, the crunchy tar, comes from some smoldering and some damp wood; it takes a stiff brush and more passes but it comes out. Stage three, the hard shiny glaze, comes from cool smoky fires in a cold flue, exactly what an overnight burn with the air turned down does in an uninsulated exterior chimney. It does not brush off, it ignites at a lower temperature than the others, and it burns hottest. The glaze band told us the family loaded the stove at bedtime and choked it down, and the wood pile in the yard told us it was split that summer.

Removing it, and not making it again

We chipped the glaze with a rotary head and swept the rest normally. Then the advice: split next year’s wood now and stack it off the ground with the top covered; run the stove hot for half an hour after loading before turning it down; and consider an insulated liner, because an uninsulated flue on a north wall will keep glazing no matter how well they burn. They took all three. This fall the flue was stage one from top to bottom and the sweep took half the time.

If this sounds like your house: we handle chimney and wood stove sweeping across Kankakee County, and our Bonfield page covers what we usually find there. Call (815) 449-4264, 7am to 9pm, any day.

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