STONE0 T
CONTRACT12 T
HEAT TO FLUE0%
OVERBURN RISKNONE
THE CHARGE
NOTHING READ YET
THE KILN IS COLD AND THE CHARGE IS STACKED
LIMEKILN
Limestone goes to quicklime at about nine hundred degrees, and it takes two thousand degrees of heat to drive the carbon dioxide out of it. You cannot measure the middle of a kiln, so you stack the fire where you want the heat to go, stoke it, and read the fire by its colour and its noise at the trial hole. Burn it too cool and the lime is grey and swells in the store. Burn it too hot and the lime sets, and sets late, and puts a man into the slaking pit.
Stack the kiln
The old kiln at the bottom of the yard.
Slag it
The lime is out of the kiln and lying in the pit. Somebody has to put water on it.
Grey lime will not slake now. It will swell in the store and burst the wall.
Paused
Nothing burns while you think.
The charge, the flame, the trial
- THE BURNING FRONT
- The section on the right is the only view you will ever get of the middle of the kiln. Courses you have taken a trial at are drawn solid. The rest is hatched, because it is a guess drawn between the courses you have paid to look at.
- STOKING
- Holding the stoke key throws wood on the firemouths and works the bellows on a fire that is going back. A stoked fire burns hotter and faster, and a hotter fire sets the lime.
- THE DAMPER
- The flue damper. Wide open and the fire draws hard but the heat goes up the flue past the stone. Shut it and the kiln holds its heat and the fire smoulders. The chimney pull follows the temperature of the stack, so a hot kiln pulls whether you want it to or not.
- CO2
- The reaction is retarded by the carbon dioxide it makes. A course that cannot vent keeps its own product around it and stops converting, which is why the front stalls where the charge is tightest.
- GREY LIME
- Stone that never reached temperature comes out as the stone that went in. Water will not slake it. It swells in the store days later and bursts the wall.
- BURNT LIME
- Lime held above fourteen hundred degrees sinters shut. It looks like good lime and it slakes like good lime — right up until two hours after the water goes on, when it goes off like a gunshot and takes the men at the pit with it.
A good firing
The stone came out white and it slaked when you put water on it.
PASS54 HOURS
The season is closed
Four kilns, one winter.
ATHE KILN MASTER’S MARK