Plaster and Cob

After a couple hours or slicing slimmy barrel fruit for chutney Michela (the other intern) and I collected plaster that had weathered off a straw bale wall that was constructed and plastered over 16 years ago in 1994. The wall was constructed back when people thought chicken wire was a good material to put between the straw bale and the plaster.  Now it is not recommended and plaster is applied directly to the bales.    The plaster had collected at the bottom of the wall and sifted it so we could reuse it to re-plaster the wall.  This plaster is a combination of sand, clay, fiber (manure, hair, straw) and ferment (manure and cactus juice).  “Its all connected and it’s all good” -Barbara Rose

the falling plaster

Michela sifting plaster

the wall after we removed the fallen plaster

We also made a batch of cob for an upcoming cob workshop at Bean Tree on Saturday.  To make cob you need the right kind of dirt, it must be at least ten percent clay.   To determine this there is an easy way to test it; I will explain that on a later blog.  You must screen the dirt through a ¼ inch screen to get out all the rocks and large organic particles.

How to make cob:

1: In a pile of screened dirt (on top of a tarp) you make a well and fill it with water.

step 1

2: Using your feet you create a homogenous substance, adding more water if needed.

step 2

You can pull the corners of the tarp inwards to aid in the mixing.  The cob should be the consistency of cookie dough, not too sticky.  However because the dirt here is mostly clay this batch of cob will stick to the tarp a little more than usual.  Most batches will roll clean off the tarp.

3: Once you have reached a good consistency you sprinkle straw over the mixture and continue to incorporate it.

step 3

It is important that the straw is not rotting.  It is ok for it to be wet, some people even soak it overnight before they use it, but it cannot be wet because it has been sitting and decomposing.  That would allow mold and unwanted microorganisms to grow in the cob.

Interesting Fact:  In Britain there are 4 story high cob cottages

This was my first time making cob and I was surprised at how easy it was.  I feel like it would not be hard to make cob even with very limited experience.  I will be posting more about the process and also how to build with it later on.  If you have any questions I will be glad to answer, you can leave comments or send me an email!

Here is a cool cob video…

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