– by Ed RaduazoWattle is a woven backing. This dome-shaped woven backing was created from the ground up. Daub is a mixture of clay and cellulose. Traditionally the cellulose comes from the dung of grass eating animals. The animal's digestive system removes sugars, carbohydrates and proteins that we do not want in our wall, and what remains is cellulose.
I have found that most US citizens do not like working with dung. Dung is not a part of the US culture and experience, but sources of cellulose are everywhere. One of the most easily accessible sources of cellulose is shredded paper, which I have been able to turn into pulp by soaking it in water while treading it by foot. It takes a little time and patience to work with light weight crew, but every once and a while I turn the pulp with my hands and check it by treading it for a few minutes to speed the process along.
The next step is to get some good sticky clay. We were lucky to have a pile of dirt scraped up by grading in back of the church, and it only took a few minutes to have my crew run it through a 1/4 inch rabbit-wire screen.
After this, we put the pulp and clay on a tarp and began mixing it in a fairly conventional manner. Normally we say that water cannot be pushed down into dry dirt, but in this case, wet pulp cannot be pushed down into dry dirt. Once the dirt and pulp are on the tarp, we roll the mix so that the dirt is on top, and then tread the dirt down through the pulp with our feet, roll the mix, and do it again, adding water as needed but not too much, because we want a highly viscous mix thick enough to span gaps between adjacent wattle.
As you can see, spaces were left between some of the wattle strips so that "truth windows" would let in light and allow occupants of the structure to peek out. In places where the gaps turned out to be too large, we wove in supplemental strips of bamboo to make plastering easier for my youthful crew.
Rolling and treading on a tarp created a sticky, uniform mix of paper and pulp. To a batch this size I added a gallon of Elmer's milk glue to act as a water repellant, and we began plastering.
The primary plastering tool consists of our hands. Balls of mud were turned into pancakes and lightly patted into place. We told the kids to press the mud into the grid and then pat it like patting a dog. Many light pats work much better to make the mud flow and smooth than a few heavy slaps. We then smoothed the mud. Plastic container lids like those on cottage cheese work well for this purpose. I like to embed colored plates of glass in the mud to form lights.
It took about three tarps of mud and one day to do a first layer on this structure. I like to plaster the outside on the first day and then let it dry. Do the inside and let it dry and then do the finish plaster. Because of the large number of kids I let some of them work on the inside as a team with someone on the outside. By pushing the mud from both sides I thought we could get a better bond and do both sides at once, but I think it tended to just make a mess and there was a lot of mud on the floor to clean up at the end of the day.
My preferred system is to plaster the outside and let it dry for a few days so that the mud is firm, but sill moist. I then plaster the inside with a slightly wetter mix. Instead of patting the mud as we did on the outside, I put a ball of mud in the palm of my hand and pump it into the nooks and crannies with a side to side motion using the palm of my hand.
Note on tools: The first and best sculpting tool, of course is your hands, but the second best are home made smooth surfaced objects from around the house. Lids from cottage cheese containers (cut off part of the lip for a flat smoothing surface and the remaining lip portion serves as a handle), spoons, butter knives bent into a Z-shaped configuration, short pieces of rubber tubing and many other objects found around the house can make great sculpting tools.
The clay can be screened through a 1/8 inch screen instead of a 1/4 inch to make a finer finish. Alternatively you can purchase something called “fire clay” at larger brick supply places or purchase clay from pottery supply stores. Often these places give you a variety of colors and since you do not need very much it can still be reasonably priced. The finish layer will have a higher percentage of white glue to make it more water repellant.
My crew appears in the above slideshow. They range in age from 5 to 65 and a great time was had by all.
Below you can see the truth windows. Note the feet seen in the picture are bricks placed between the vertical strips of bamboo which we jammed into the ground when we started to weave the structure. This foot pattern is repeated on the inside of the structure and besides being ornamental, it acts as a padding over the corners of the bricks.
When people ask me to teach natural building classes, especially finishing, I often feel a little bit overwhelmed because they often want to learn all about a natural building process in one morning or one afternoon. That is, of course, impossible.
Some things can be learned but not taught. For example, people are often fixated on recipes:. how many parts of this and how many parts of that to make perfect cob or earth plaster? The problem is that every part of the earth's surface differs from every other part of the earth's surface so a recipe that works well for my back yard might not work in my neighbor's back yard. I know when a plaster is not sticky enough, but how do I teach that to you?
Many things about finishing are a matter of preference. My favorite plastering tool for earth plaster is my hands, but I also like steel trowels and plastic strips like those made from the lids of cottage cheese containers, but some of my friends are just as convinced that wooden trowels are the best. My goal is to make a surface that is so smooth and non-porous so that water will hit the surface and run off. I want no nooks and crannies in the wall that will hold water, and no horizontal surfaces that will stay wet for a long time. For my money, metal or plastic trowels form a smoother surface that will shed water and dry faster, but is that fact or opinion?
I don't know what I don't know. I am convinced that shredded paper is superior to horse or cow dung when making finish plaster, but I have done no tests to conclusively prove this. I believe with a fair amount of certainly that mixing milk glue (Elmer's glue) with earth plaster makes the plaster more weather resistant, but I have done no tests to prove this. I don't know how much glue should be used with how much plaster. One coat of linseed oil seems to repel water two coats of linseed oil causes the surface to turn black with age.
The advice below is to the best of my knowledge and should be taken with a considerable grain of salt. The plaster; like the finish material; contains a lot of paper; perhaps as much or more than the amount of clay. As your paper level goes up and the clay level goes down your mix becomes stronger, less prone to cracking and less and less sticky. Eventually it will not stick to the dry layer of plaster so I would say that if it feels good and sticks well it is good. If later it cracks try a thinner layer to cover the cracks. If it peels off add more clay.
An image in the collection above shows a primer layer of clay slip (the dark reddish brown color) followed by a red finish layer. I believe that the slip improves sticking. Slip should contain just enough clay so that when you dip your hand in it you should not see your finger prints. The clay contains one gallon of Elmer's glue with 20-25 gallons of plaster. The grey or light brown clay is from a deposit in my back yard, the red comes from a friend’s yard. The reddish brown slip is discarded clay from a place that teaches pottery. The contrast clearly illustrates the importance of keeping a sharp eye out for clays of a different color.
I noticed many cracks in the plaster layers covering the bamboo, but none in the finished plaster. To me this seems as it should be. You will notice that I have said nothing about sand. I did not add any. Paper fibers will resist erosion by water, sand resists wearing away by friction. While I would put a lot of sand in a floor I use little or none in the outer walls of my building. This may be another case of not knowing what I don't know. I do know that this will last for several years. I don't know if it would last longer with sand. I do hope that some day someone will sit down with all the possible combinations and do a series of experiments that will prove conclusively if sand improves the mix, but that is not something I have time or energy enough for at this time.
Several children complained that the inside of the house smelled bad when it was drying. Milk glue is quick to ferment this should be expected. Now that it is dry it does not smell. We have several cross purposes here. On the one hand I want to build a structure that will last for several years. On the other hand I want a structure that is so non-toxic that you could break it up mix it into the earth and grow tomatoes in the mix next year.
Let me finish with a true story: Around 60 years ago the United Stats Department of Agriculture made an amazing discovery. They found that they could chemically add extra hydrogen atoms to long chain hydrocarbons like peanut oil or cotton seed oil to produce a grease-like substance that never got rancid. This meant that they could make up cake mixes with flour, oil, powdered egg and milk and then make a cake by just adding water and baking. You could also add food coloring and salt and it looked and tasted sort of like butter. Both the "butter" And the cake mix had a long long shelf life because they never got rancid. The USDA called this new stuff olio margarine and/or partially hydrogenated vegetable oil.
The dairy industry objected to this new "butter" saying that since it was chemically manufactured it might not be good for our health, but the USDA overruled all objections with a doctrine of equivalence saying that it was generally recognized as safe.
Thirty years later, I was talking to a friend of mine named Price Faw in the Patent Office search room. He told me that no male in his family, in modern times, lived to retirement age. Fifty five years of age did not seem to be a particularly lofty goal since his grandfathers and their brothers had lived into their 70s and even 80s.
I did not know what to tell Price at the time. No one did, but unbeknownst to us, the Framingham Heart Study had already noticed a dramatic increase in the number of heart attacks and strokes in the United States. They would later conclude that saturated fat the cause and then later amend that to say it was all or mostly the partially hydrogenated oil that was causing heart attacks, but that information was 15 years too late for Price Faw, who died at the age of fifty four.
Our sense of smell developed over thousands of years to tell us what is good to eat and what is not good to eat. We should not extrapolate this to apply to our building materials. I once stayed at an adobe bed and breakfast in Texas. The house we stayed in was more than 100 years old, and the owner was in the process of building an additional unit with "stabilized adobe". His main objection to the new adobes was the $1.00 each cost. My objection was that they had a very faint smell of crank case oil. I asked owner what the blocks were stabilized with and he did not know.
I would not go so far as to say that smelling bad is good, but the fact that a finish material will ferment or go rancid from sitting around too long indicates that it is biodegradable. Mold is not good, but I have never had a problem with mold in any structure that remains out of contact with liquid water. I live near Washington, DC on the Potomac River, a place never known for dry climate. I would regard the persistence of a bad smell or the appearance of a bad smell after many years of no odor as a sign that something needs to be done, but it is not a reason to avoid natural building materials.
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