Last weekend I went to a Sustainable Living Festival at a nearby farm. In addition to about a dozen lectures that I listened to, I also took a cob building class. I've been super interested in cob for years and actually wanted to build our home out of cob ... before we found and bought the one we live in now.
So, now I'm thinking ... cob chicken house.
What's cool about cob is you use what you have. It's a great self-sufficiency skill to acquire. The most common materials are: clay, sand and straw. But again, you use what you have. Bailing twine, sawdust, the earth you dig up from your back yard.
First you lay down a tarp if you don't want the ground to get all icky. Also it helps for rolling logs, as you'll see later. Our instructor, Keiko, laid down sandy soil first. He got this from a river bed.
Then he added clay dug from the ground and dried in the sun.
We all started smooshing it together with our feet. Mine are the red toes.
You add water to get it nice and wet.
Keep stomping and squishing.
Then you do a ball test. Make a ball in your hands and pat it down real good ...
... then you drop it. This batch isn't quite done yet. Needs more sticky stuff. So we added more clay and water.
For this particular demonstration, Keiko was having us make a cob oven. It was a mini one.
First you've got a base (simulated by the milk crate and wood lathe thing), and then you lay down your fire brick.
Keiko interrupted his demonstration to show us some bricks. Instead of free forming with cob, you can also make bricks with a form like this.
This is a cob brick. (It is unfired and used to build in this form.)
You can also fire cob bricks in a kiln (like pottery, 'cuz -- duh -- it is pottery) and they end up looking like this. And they last a really long time.
So back to the oven. Once your cob is ready, you build a sand castle with wet sand. :) This is what you are going to put your cob on.
For this little oven, Keiko had us make the walls of the oven be two fingers thick. It's important to keep your measurements the same all the way up to the top, otherwise you end up with a really thin dome top. Push down on the clay, compressing it but not pushing into the sand.
If a crack happens. Oh well.
Just cut out the broken part and keep working.
Here's all the cob put over the sand form.
Use a piece of wood or a paddle to smack it around a bit to further compress the clay and work out any lumps or weird pooches in the walls.
And then the walls are all smooth.
Cut out a door.
And dig out the sand.
Keiko talked a bit about insulation next. On an oven, you want to keep the heat inside so it doesn't cool off too fast when you pull the fire out to cook in it. (I imagine you'd want insulation on your house, too.) You can actually go up to a foot's width of insulation. At least six inches. Here he's made an insular layer made of sawdust and pottery slip. ('Cuz that's what he had.)
Our next project was a quicker way to make cob that was nice and strong and could be used for walls and such.
Take your cob mixture: sand, clay and water; and add straw. This isn't so much mixed in, as stomped on. Think "squash the grapes." The idea is to keep adding straw and dancing on the whole pile until no mud squishes up between your toes. You don't want a sloppy cob to build with or your walls will smoosh over.
When it was dry enough, we rolled the tarp over and consolidated all the cob together into this log that was strong enough to stand on.
Now you can start building with it. Same as before, compress and integrate the layers together. Don't just lay them on top of each other.
Alternately, you can make coils. (Good for curved walls.)
Now make a giant coil pot!
I got lots of ideas and I'm so glad I went. Next step, dig a hole in my back yard and start drying my clay soil out.
Tuesday, June 30, 2009
Tuesday, June 23, 2009
This is the part of their forest that they sustainably harvest. Note what this side looks like compared to the wild forest that they leave alone and don't touch.
This is a cool building that they are finishing up construction on. You can see all the layers here. First there is straw, then a mud/cob layer, and then a lime wash plaster.
This is the wilderness part of their forest. This was my favorite part of the tour.
Jeremy, our guide/instructor, is showing Aubrey a "writer's conk". Named for the under surface of this fungus: you can carve messages for future travelers to read. Writer's conks only grow on dead trees.
This is the wilderness area where they don't touch anything. Nothing is removed (as in felled trees, etc.). Do you see the difference between this and the harvested area?
Jeremy identifying a Big Leaf Maple. Maple leaves have five sections to them. (maple=5 letters) Another species version is the Vine Maple. There are nine sections to those leaves. (vinemaple=9 letters)
This is another legacy stump, but it's also a "nurse" log, because a new life form is growing out of it.
This is not a nurse log. This tree fell over in the forest but did not die. Instead, the branches grew up and up to resemble trees. It was pretty neat-o to see.
This forest is fifty years old. Aprovecho purchased some land fifty years ago that had been pretty much clear cut and they planted all these trees. Except for three trees. One of them is to the left of the picture. It's a hundred years old. As they sustainably harvest the trees in this side of their land, they'll always leave those three old trees, and a few of the middle-agers. They use the lumber they cut down for building their houses on the property and for firewood.
They also leave dead trees, or snags, for the purposes of encouraging wild birds and mammals to live in them. They eat the larvae and beetles and termites that can sometimes bring a load of trees down.
Aubrey and Robert are using the metal ox to pull a downed tree to the bottom of the hill where it can be milled for use.
This was a super cool cob bench. You can't see in the picture, but there are a couple of "steps" for sitting on below the kids' feet. They used the clay from their own land to create the cob.
The day finished up with a rocket stove specialist sharing why rocket stoves (like the small one shown above) are more fuel efficient and also much healthier to use. His team has gone to neighboring countries that tend to cook over open flame in their homes, without proper ventilation, and showed them how to make rocket stoves themselves with the raw materials that they had and how to repair them when they broke. Helping others learn how to be self-sufficient is part of the educational curriculum at Aprovecho. Our guide also shared that respiratory disease is the number one cause of death in children under the age of five. So it was real important to cook away from the house, outside; or to have proper ventilation inside so as not to inhale the black sooty smoke day in and day out.
The people that teach on Aprovecho also live there. It is an intentional community.
Our "school", Homesource, is a place where my children take classes in stuff that interests them and they come up with some pretty awesome field trips from time to time. This was one of those times.
I haven't decided if Homesource is for us, because of course there are strings to everything and I don't particularly like these strings. But we'll try it for another year and see.
I'm real glad we went on this field trip. It was great to get the kids out in nature and do some hands on activities (like logging!) that they don't/won't get anywhere else.