Ojinaga, the painted city

We went to Ojinaga several times during the Adobe Alliance workshop. I loved it because it was so colorful:  almost every building is painted a really imaginative color, and no two are the same.  Houston is so gray and boring by comparison.

Also, most of the commercial buildings had signs painted on them by hand.  The signs were often pictures of what was for sale in the store, along with words about the business.  I realized suddenly that in the states, most ads are photographs nowadays, rather than paintings.  It's kind of a loss.  These hand-painted ads are beautiful and wonderful and varied and weird sometimes.  There must be lots of sign painters in Ojinaga.  It would be a fun job.

This foxy lady was painted on the outside of a store that sold fancy dresses for weddings and quinceaneras:

A bar called the "Lolita" had a slightly racier girl on it:

 

Is this Humbert Humbert's Lolita?  I wondered because I am reading Reading Lolita in Tehran.  Do they read it in Ojinaga?

 This painting of a cowboy on a horse was on the outside of a restaurant. 

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This one was on a grocery store.

 

Because we had been learning about painting on plaster on adobe, I wondered if the tradition of decorative plaster on adobe buildings had caused this efflorescence of painting on regular cement stucco.

Adobe arch

One day some of the participants in the workshop made an adobe arch.  They made a form out of adobe bricks, arranged in a sort of post and lintel way, and they draped some black plastic over the blocks. To make the form more rounded, they packed some clay and straw on top of the  adobe blocks, under the black plastic.

Then they stacked the adobes and mortar in an arch shape over the form.  (It's also possible to use a plywood form.)  It dried for a day or two, and then we tested its strength.  It was surprisingly strong!

We decided that it was a triumphal arch for a dog. A dog could run through it after catching a rabbit, for example.  But the dogs that were there wouldn't try it out.

Plaster

On the last day that I was at the adobe workshop, we learned about plaster, a fascinating subject.  Jesusita Jimenez had told us that she considered plaster to be the most important, make-or-break aspect of an adobe house.

We made several batches of plaster to check which one would work the best on the particular wall we were working on.  It was the wall of one of the vaulted outbuildings at the Swan house.  Stevan told us that with any adobe project, it is necessary to do this trial and error testing to get the mix of clay, sand, and straw right for the particular conditions of the site, and the particular qualities of the ingredients you are working with. The objective is to get a plaster that won't crack as it dries.  The clay is the element that causes it to stick like glue to the side of the building; the sand and straw keep it from cracking.

We started out with a mix that was one part sand, one part clay or dirt, and one part chopped straw.  The sand and clay had been sifted through a 1/4" screen, and the straw had been chopped in a leaf eater machine (essentially a weed eater in a plastic funnel).  Plaster can be mixed in a mortar mixer or with your hands.

We plastered this on the wall using hands and trowels, working upwards rather than downwards, and feathering the plaster at the sides as it met the walls.

We also tried three other mixtures, with a bit more sand and straw. Test number two for example had one part clay, one part straw and one and a half parts sand.

When the coarse plaster had dried a little, we put a finer finish later over it.  That was when it really got fun.  The finer finish layer just had finely sifted clay and sand.  You can also add color at this point:  we added some yellow color.

 

I thought this was really beautiful, and I got excited about the decorative possibilities:  I began inscribing the wet plaster with spirals.  At that point Stevan told me that there are whole workshops devoted to plaster artistry at the Canelo workshops in Arizona.  I looked at their website and got very excited. Maybe I will make an earth structure darkroom at my farm just so I can decorate the walls with earth plaster.  An adobe vault wouldn't work in Tennessee, but earthen walls of cob or adobe or stucco over straw bale with an adequate roof and foundation should work.

Jesusita Jimenez

Ms. Jimenez came to talk to us toward the end of the first week of the workshop. She grew up in an adobe house, and she had a lot of interesting things to say about her experiences building with adobe.

Ms. Jimenez was the project manager for Simone Swan's house in 1998, so she knew about its construction in intimate detail. The original plaster was earth, sand, and straw. But on top of that was a lime and cement covering. It was painted blue, over the lime and cement. The original lime and cement plaster began to crack eventually, and the cracks leaked. So that original plaster had to be removed, at great expense. That plaster was replaced by a natural plaster of clay, sand, straw and prickly pear juice.

The prickly pear (nopal) pieces are chopped with a machete and left to macerate in water for four to five days. Then the "tea" is scooped out and added to the dry ingredients, along with some manure tea.

Ms. Jimenez said repeatedly that sand and soil have changed since she was a child. It is not as easy to make good adobe as it used to be when she was a child. She said that when she was little, she and her siblings made an adobe play house that lasted for years; but now it's harder to get the adobes to stick together and be hard. She thinks it's because the soil is polluted.

When a lime plaster is added over the first layer of clay, sand, and straw plaster, it has to dry slowly, in order to be durable. One way to do this is to lay wet sheets over it while it dries; or one can sprinkle water on it periodically while it dries.

Ms. Jimenez believes that re-plastering should be done once a year. This was traditionally done when she was a child.

Carlos house

Somebody left a comment asking some questions about the house in Ojinaga that I wrote about a few days ago. I can't figure out how to respond directly to comments in Blogger, so I will respond here.

The house does have a lime plaster, but I'm not sure if it's the same as the plaster on the Kern house. I think it has two vaulted rooms in front. Not sure if it has any flat roofs or not.

I have one picture of the interior, showing the squinch that supports the dome.



Simone Swan explained to us how the squinch works and how it is built. The purpose of the squinch is to enable the builders to put a circle on top of a square: it makes the square building into an octagon. When the walls reach a certain height, a form is used to build a little arch in each corner, over the form. Then when the arch is dry, the wall is built up to the top of the arch, creating a new octagonal wall on which the dome rests.

Oregon cob; Jesusita Jimenez

On Friday we had an Oregon cob demonstration. Oregon cob is another form of earth architecture, developed in the Pacific Northwest, but based on ancient building techniques that were used in Devon and Cornwall in England for centuries, and also in the southwest of Ireland. In cob construction, you don't make bricks and then stack them, as in adobe construction; it's a "monolith," in the sense that the wall is like one big adobe brick that has been formed gradually. You start forming a "course" of cob on top of a stone foundation and you work all the way around the foundation; then when that dries, you trim and shape it a bit and start the second course.

The first thing to do is mix the clay and sand, just as in adobe brick making. The clay and sand are shoveled onto a tarp, and then mixed together by rolling the tarp. (Both were sifted first through a 1/4" screen.) The clay makes the mixture stick together, and the sand gives it compressive strength and prevents cracking.

Then you add water and mix with your feet.



Straw is added to give tensile strength to the mix. (Sometimes manure is used also because it too has fibers in it. The fibers in manure have been chopped up a bit more, obviously, by the animal's teeth and digestive system.)



Finally the cob is shaped into a loaf-like shape on top of the foundation. The cobber uses his thumbs to push down into the cob. This causes the cob mass to cohere, and it also creates a surface for the next layer of cob to stick to. It's a bit like a wet mushy lego.

It's interesting that walls can be formed without bricks or even forms .

Cob walls are often very thick, as much as 24" thick. The first course is often wider than subsequent courses; the walls can taper as they go up, but usually they are never less than one foot thick. A rule of thumb is that for every one unit wide the wall is, it can't go over ten units high, but in practice, according to our teacher Stevan, this rule is sometimes violated to no ill effect.

A thin coat of lime and clay is often used as a plaster on the outside and inside of a cob wall.

Cob houses usually have framed roofs, but it's possible to make an arch by corbelling the cob inward gradually. I'm not sure if cob vaults are possible, though.

Simone watched the cob demonstrations in a beautiful North African style robe that she sewed herself from fabric she bought in Ojinaga. (More about that later on my other blog, All Fibers, All the Time.)

Later that day we met with master adobe craftswoman Jesusita Jimenez. Jesusita was the project manager for Simone's house and several other adobe houses in the region. She is retired now from adobe building, but her influence is still felt in current adobe construction. Her craftsmanship, precision, and speed in adobe masonry are legendary. She is shown here with El Maestro, Sevan de la Rosa, our teacher during the adobe workshop. I'll write more about what Jesusita had to say in my next post.

Keystone

It's not all hard labor at the Adobe Alliance workshop. The other day we took a day off and went to Chinati Hot Springs near Ruidosa, TX.

Chinati Hot Springs is a remote little low-key resort on the border between Texas and Mexico. Vaux le voyage!

The next day we achieved a milestone: the first keystone at the top of the arch. Efren, a master mason, quickly cut a small adobe with a trowel to make it fit the space perfectly.


We made a field trip to Mexico and looked at another adobe house with vaults and domes. It is smaller, and it is not finished yet: the doors and windows have not been added yet.

This house was not built by the Adobe Alliance.



The owner is from Lebanon, thus the Middle Eastern style of the building.