Real progress

There was a lot of progress made on the kiln today. I've been preparing many pieces and parts, and it was gratifying to see them go up smoothly.

First the angle iron went up. Howard drilled holes into the concrete through flaps on the bottom of each vertical post. The posts are then bolted onto the ground. Stainless steel tie rods were added at the top of each angle iron to stabilize the tops as well as the bottoms. We added valve springs onto the tie rods on top to absorb the expansion of the arch when the kiln is at its hottest.

As we erected the vertical irons, sheet metal with kaowool insulation adhered to it, was slipped into postion. The kaowool is spun alumina, a space-age insulation product that works best when it is not compressed. I had the sheet metal edges folded in a z-shape, so the sides would fit under the angle iron, and the center pooch out to give space for the insulation.

The first photo is the front of the kiln where you can see the wooden arch support above the sheet metal. A close examination shows 8 rows of bricks on each side of the arch support. There are another 11 rows of bricks to be added in the middle/top of the arch. When all the bricks are on the arch support, it is carefully lowered just a fraction of an inch to make sure nothing falls. There is no mortar on the arch bricks or skewbacks, they are held in position by the shape of the arch. Angle iron & tie rods keep the arch bricks from spreading or falling. When we are confident the arch is holding (of course, it will!) the wooden support will be removed from the kiln.

On the left side of the kiln front you can see the white kaowool insulation through holes in the sheet metal. The upper hole will be cut out to reveal the opening where wood can be stoked, and the lower hole will be for a propane burner. There are similar holes in the sheet metal on the back wall. You can see them on the second (right side) photo. The back of the kiln can be seen on the left and the firebox side is on the right of the photo on the right side above. Holes on the far side of the back wall are peep holes, which when opened will allow me to check the heat rise during a firing. The holes on the bottom of the firebox side walls are called "mouse" holes. When these are opened during a firing, they will allow fresh air (more oxygen) to enter the firebox. This would be to encourage a hotter wood fire, when that is the fuel being used.

After the arch bricks are set, I get to go back to mortaring bricks on the front & back walls. My supply of good hot-face bricks is getting very low. I'm trying to use the better looking (newer, less chips or gouges) bricks in the main kiln, where it will get hottest. The chimney can take any left over, old, cracked, chipped or otherwise compromised bricks, and it will not affect the way the kiln fires. I have a number of old soft bricks that I'm planning on using to insulate the chimney until I run out of them. We'll see how much of the chimney will get insulated this way.