strawbale greenhouse with earth plaster

[edit] Plaster The first layer of stucco is a clay slip. This is made of clay that has been put through a screen, soaked in water, and blended into a creamy texture. When we had 50 gallons made we rented a plaster sprayer to apply the mixture onto the walls. If we did not have this sprayer we would have had to apply it by hand which would have taken a long time and we could have never gotten it to penetrate the walls deep enough. The purpose of the clay slip is to create a surface to which the rest of the stucco can bind to.(Fig 21) To mix the second layer, which is called the scratch layer, we rented a cement mixer. This layer is a combination of sand, clay, and straw and is the consistence of brownie mix.(Fig 22) We applied the scratch layer to the bales after the slip had dried a little. This is a thin layer put on by hand into which we made horizontal lines with our fingers so that the next layer would sick to it. When applying the scratch layer it is best to start on the bottom of the wall and work your way up pushing the mixture in an upward direction.(Fig 23) The third layer or filler layer was mixed with our feet on top of tarps. This layer is made up of the same materials as the scratch layer but the proportions are a little different. There is less clay, less water, and the pieces of straw are longer.(Fig 24) As with the last layer it is important to work in an upward direction so that each piece of stucco is bonded with the one below it. We would mix up a small amount of filler and break it into small hand sized balls that we applied one at a time dampening the wall before sticking them on. There are a couple of reasons why it is important to dampen the layer underneath before adding new material on top. One is to help the new stuff stick and two so that the layer beneath it does not suck out the moisture from the one on top and cause cracking. With this layer you can take out all the impurities of the wall. If there is a little hole you just fill it, hence the name filler layer. The application of this layer was extremely time consuming and took approximately 120 hours by itself.(Fig 25&26) Once the filler layer was complete it was time to do any artwork that we wanted on the walls. The artwork is done with the same mix as the filler layer and is like working with clay in ceramics class. It is important to make your designs much bolder than you want your finished product to be so when you add the last coat of stucco the detail is not lost.(Fig 27&28) The preparation of the materials for the last coat took a long time. The last coat is made up of horse manure, clay, sand, and flour paste, all of which had to be processed. The sand was run through a 1/8 inch screen(Fig 28), the manure was pushed through a ¼ inch screen(Fig 29) and the clay needed to be blended into the same creamy consistency as the slip. Fortunately, we had some help with this process from a class at the local university. Once the materials were ready we mixed them like the last layer, on a tarp with our feet, and applied it to the wall by hand. This layer did not have the right ratios and had to be redone later due to cracking. The lesson we learned here is to make sure that your test strips are right and you have the proportions correct.(Fig 30&31) This is our test strip bale. In the future I will make all of my test strips about twice as big as what I did here so that I get a better feel of how it will look when it dries.(Fig 32) The mistake in our plaster turned out to be not enough sand or horse manure. Our final ratio was two parts sand and horse manure to one part clay and lots of water to make it go on easy with a trowel.(Fig 33)

via Kiva’s straw bale greenhouse – Appropedia: The sustainability wiki – Mozilla Firefox.

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