Now I just need a door :)
While digging out the door, I was worried I was going to dig through the sand and into my cob. The first layer of cob I used was just dirt and clay, no sawdust. It was already fairly sandy when I was digging through that layer, hence the concern. However, the newspaper I put on top of the sand really did help. In fact, as soon as I got a good amount of sand out, the rest caved in cleanly. Now I'm waiting for it to dry (we have hot days coming, yay!) a little bit more and I need to make a door for it. I should also chop up lumber that will fit in there, as all my logs are currently too big.
The way I made the cob:
I had bags of reclaimed clay from the ceramics department. I would fill them with water and wait a day as most of it would turn to slip. I'd pour this into a wheelbarrow and add more water. I'd add dirt until I got the desired consistency of being just a bit too wet, and then I'd add sawdust. This got rid of moisture and provides air pockets in the cob which is important for insulation. I did this by eye from the first ball tests I made, and I really wanted a little less than half clay to half soil. There wasn't too much clay already in the soil, but it was wonderfully sandy. At home I'll be applying the same technique by watering down the boston blue clay I have overnight and then adding soil. I could buy bags, but the reclaimed soil/clay is fun to work with. Dry bags would be a pain anyway because I'd have a lot of floating silica dust if I spilled one for instance. For the outer part of the oven because I've been running out of time I applied a layer of clay slip to protect it from rain a bit. This oven is so temporary I didn't want to go through the trouble of making plaster yet. I'm going to be keeping it under a tarp while I'm using it anyway.
So some time in the next week I'm going to fire this baby and hopefully use a thermal imaging camera to watch and monitor the heat within the oven. I'll obviously post all of that wonderful data here!
