Kilnstruction
Feb. 3rd, 2018 04:16 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
offcntrHad a couple of less-than-optimal firings just before Christmas, so I decided to see whether a little kiln maintenance might help. I already tightened up the chimney back in December (the bricks expand and push apart over many firings. Gaps allow in cold air that reduces the draft).
Today's repairs:
1. Take a vacuum cleaner to the burners, clearing out scale and detritus from the venturis.
2. Tear down and rebuild the bag walls. These are hard-brick dividers between the flame trough (where the burners shoot in burning gas) and the ware chamber itself. They're about four bricks high, and divert the flame up to the top of the kiln, where it will be drawn back down through the pots and shelves before exiting through a flue in the floor (and isn't that a tongue-twister). Extreme heat on the outer face has caused them to lean toward the outer wall, constricting the flame as it enters the kiln chamber. I tear them down to the bottom layer, reversing most of the bricks--they've actually started to warp, a little--and shimming them up with ceramic fiber to true them up vertical again.
3. Tighten up the bricks of the door, mostly by banging them with a hammer and two-by-four, to eliminate gaps and get the door face mostly flat again. I also brought in wrenches to tighten down the tie rods that hold the bricks in place in the steel work. We really need to get some new valve springs--the pair we have now are almost crimped flat. Automotive valve springs are often used in kiln frames to allow for expansion and contraction with heat. This set seems to have given as much as they have.
I'm hoping this will make for a better--at least more normal--firing Monday.
ETA: Aaand, it seems to have worked. Cones dropped together, same temperature top and bottom from about cone 1 all the way to the end. Used 64 units of gas, substantially better than the last two outings. Could even trim that down a little next time, as the reduction was pretty heavy throughout, could be a bit less.
Today's repairs:
1. Take a vacuum cleaner to the burners, clearing out scale and detritus from the venturis.
2. Tear down and rebuild the bag walls. These are hard-brick dividers between the flame trough (where the burners shoot in burning gas) and the ware chamber itself. They're about four bricks high, and divert the flame up to the top of the kiln, where it will be drawn back down through the pots and shelves before exiting through a flue in the floor (and isn't that a tongue-twister). Extreme heat on the outer face has caused them to lean toward the outer wall, constricting the flame as it enters the kiln chamber. I tear them down to the bottom layer, reversing most of the bricks--they've actually started to warp, a little--and shimming them up with ceramic fiber to true them up vertical again.
3. Tighten up the bricks of the door, mostly by banging them with a hammer and two-by-four, to eliminate gaps and get the door face mostly flat again. I also brought in wrenches to tighten down the tie rods that hold the bricks in place in the steel work. We really need to get some new valve springs--the pair we have now are almost crimped flat. Automotive valve springs are often used in kiln frames to allow for expansion and contraction with heat. This set seems to have given as much as they have.
I'm hoping this will make for a better--at least more normal--firing Monday.
ETA: Aaand, it seems to have worked. Cones dropped together, same temperature top and bottom from about cone 1 all the way to the end. Used 64 units of gas, substantially better than the last two outings. Could even trim that down a little next time, as the reduction was pretty heavy throughout, could be a bit less.