Insulation on the second chamber

Finally getting around to finishing the insulation on the second chamber. There was a LOT of insulating castable left from the workshop, so I decided to use it. It’s quite a luxury to have access to so much for this job.

First, I did the front and rear walls. The front was easy because it was just framing the doorway, and I had plywood that could be clamped in place to hold the castable in. After draping fiber over the whole chamber and around the edges from the arch to the front and rear walls, started putting castable in the plywood ‘forms’.

Here you can see the castable draped over the edge, and the arch form over the door to finish that side. Both sides of the door are finished, with a little 30 degree angle built in to support the arch.

The rear wall was toughest, because the plywood wasn’t strong enough to support the castable going in, and started bowing out, which allowed castable in between the plywood and my spyhole, and stokehole placemarkers. So, the next morning when I removed the plywood I had to chisel out the holes, a little more than 3 inches where the stokehole was. Note the two test spots where I thought the stokehole was, before I checked from the interior.

This extra thickness in the rear wall is probably a good thing, since the stoking will take place there, and any extra heat is really uncomfortable. During the first firing there was no insulation, just bare brick, and the heat was unbearable. We draped fiber blanket from the arch just to create a heat barrier so we could have a place to stoke.

The rear wall got done in two days and you can see where the first and second pour connect. I did put in some mesh just in case that connection point gets iffy.  Also, I didn’t vibrate the mix enough around the peep hole and got some rough, unfilled space. I’m hoping this will not be a problem.

After the front and rear wall, I started in on the arch. The arch section curves over the edge to rest on the walls, which were finished fairly smooth. I expect the arch section to separate from the walls at this joint during firing as the arch expands.

 Last is the collection box behind the rear chamber. I put this layer of castable on mainly to seal it up, because it was leaking a lot of smoke during the first firing.

Doing the nearly vertical surfaces without forms was a challenge. I finally figured out the right amount of water on the second day. Very stiff mix, applied in softball sized balls to the wall, and pressed in slowly taking care not to shock or vibrate the built up wall of wet mixture. This worked well, and after things had stiffened up just a bit, I was able to go back over with a trowel to smooth the joints out.

 Well, that’s it for now. I expect another 2 days of work to finish out the chamber completely. Then I’ll move to the front wall of the first chamber, which I want to finish out much like the door side wall of the second chamber. I want to reduce the amount of air leaking into the front of the kiln when that arch expands, and help keep the stokers cooler.