Sunday, March 22, 2015

African Pizza Dreams

by Big T

I’ve spent the last two weeks, among other things, building a masonry bread oven according to modified plans for traditional Italian wood-fired pizza oven. It has been refreshing to work with my hands, be creative, and overcome non-people related obstacles.

The goals are fairly simple: 1) to provide vocational training as bakers to some of the kids, 2) to develop a micro-enterprise from which the kids can learn business skills and a trade, 3) to provide bread to the kids and community with proper use of local resources and appropriate technology, and 4) I’m admittedly hoping to eventually get some pizza out of the deal. This calls for building an efficient oven using local materials and which uses readily available fuel. There is a shortage of fuel of all kinds here. Basically the only readily available fuel is firewood, but even that has to be stewarded carefully, because deforestation is a major problem. All petroleum products are very expensive, often impure, and relatively hard procure. We have, over the past five years, planted perhaps two thousand trees. We can see a difference on our 66 acres already, because many of them have already reached thirty feet. Things grow fast in the tropics. They also happen to be nitrogen-fixing trees, which improves our soil. And when you cut one down, another trunk quickly grows from the stump, so our fuel source is at least theoretically renewable.

So it has to be wood fired. No problem. Wood fired pizza ovens happen to be very much in style (in the West) these days, so there is a plethora of information available. I choose a plan for a homemade backyard pizza oven modeled after traditional backyard ovens in Italy, which could easily be adapted to our needs: large scale bread production and utilization of local materials.

My seven year old has helped me often, though he tends to wander home during the heat of the day. But along the way, he has managed to learn some building skills and even some thermodynamics. My dad was here for a few weeks and all three of us worked on it together for a time. Collaborating as three generations was rewarding. I have also had two Tanzanian helpers. My main goal for them has been to teach them how to build one of these things, because it could become a good trade for them. There is not much bread around here, and what is available is poor quality and usually stale. The nearest functioning oven I have been able to locate is an hour away at a commercial bakery (which makes lousy bread if you ask me). But the local people like bread and will eat it readily. They see it as a treat. And some of them, I’m pretty sure, would also buy it. So our assessment is that not only is there a local market for bread, there is a local market for ovens. If nothing else, the young people we teach to be bakers could work in partnership with these two young oven-builders. I’m not sure how much my building assistants have absorbed. The challenge is to convince them that they could even do such a thing. They tend to think that I’m a clever and powerful foreigner while they are powerless and uneducated shovel wielders who could never accomplish such a technological feat. I realized that would be a challenge ahead of time, and the fact has been reinforced repeatedly along that way. But I’m trying to keep it simple and keep it local. Changing their view of themselves (worldview) is something that takes the power of the gospel and years to bear fruit. We go at it one step at a time. 

I also have three ten-year-old helpers who have caught a vision for the project who show up to crush charcoal and fetch water from the cistern before and after school. I’ve figured out they’re not quite ready to be trusted with the trigonometry necessary to build a perfect brick dome. Or carefully maintain the proper ratios for mixing refractory cement. But they are enthusiastic assistants and tell me they are aspiring cake-eaters. Hata mimi. (Even, me.)

The oven is theoretically super efficient because it is dome-shaped, like an igloo, and very well insulated. You build a fire inside and let the heat soak into the inner layer of firebricks for an hour. Then you remove the whole fire (saving the remaining fuel for tomorrow), and seal the door, which also seals off the chimney. The heat is entrapped in the dome and floor, and can’t go up because of eight inches of insulation over the dome. So it radiates back into the oven cavity all day long. Think of a sizzling satellite dish sitting upside down over top of a fiery hot pizza stone, all covered up by a hundred blankets.

According to my very rough approximations, our 48-inch (inside diameter) dome should be able to soak up enough heat to bake at least sixty large loaves of bread over four to six hours. Twenty loaves per load. Through the rest of the day, you can still cook other things, like meats or vegetables or whatever, and you can even put a kettle of water in there at the end of the day to take advantage of the remaining heat for you evening bath or bedtime tea. All from one load of firewood. It’s applied thermodynamics, which is all about controlling the heat by making it stop and go where and when you want it to. At least that’s how I explained it to my son. I always found thermodynamics the most difficult subject in school.

I had to do some learning about local bricks, clay, and soil. I researched via the phone, books, and local elders. Firebricks, which are basically bricks with a high tolerance to heat and a high capacity to hold and conduct heat, are hard to come by. The only truly local bricks available are of two types. One is basically just portland cement mixed with sand. The other is basically what the Israelites made in Egypt: clay soil packed into rough shape and fired in a pile—a heap of bricks with mud and straw piled over them and heated for three days. Neither of these types hold up well under the stress of repeated heating and cooling. To give you an idea of how strong they are, I will tell you that for building purposes, both types are typically cut with a machete. So we had to bring firebricks from Nairobi—not exactly local, but at least available. And they were cheap.

The next materials challenge was insulation. Firebricks conduct and retain heat. Insulation stops heat by not allowing it any conductive pathways to follow. In most types of insulation, this is accomplished via a consortium of many tiny air bubbles. Air is a poor heat conductor, and much less so when it is trapped in tiny spaces so that one air molecule can’t give its heat (molecule speed) to a neighboring air molecule. We are at 1-degree south latitude. It never gets below 60 degrees F and never above 85. Insulation basically doesn’t exist here, unless you count clothes and blankets, which are not heat resistant. We settled on charcoal, pounded into pea-sized bits, and mixed with a little cement to give it structure and to prevent it from burning by sealing it off from oxygen. We mixed these together and heaped the amalgam eight inches thick over the dome. We also spread a thinner layer under the firebrick floor.

The most interesting materials challenge was refractory cement, which is brick mortar that has the same characteristics as firebrick. Regular mortar cracks too much under the heating and cooling. It won’t hold up. I located a recipe using sand, fire clay, lime (a good heat conductor), and cement. Sand and cement are common enough, and we found lime in town, though not knowing the Swahili word for lime, it took me a long time to describe what I was looking for. The clay was a challenge. I investigated the soil near a local brick kiln, the soil near our spring, the soil in our vegetable plot, the soil used for traditional clay pots, and the soil in our neighbor’s back yard. Then, in consultation with a couple of village elders, I hit upon the solution we eventually employed—termite mounds. You’ve probably seen these six to twelve foot high brown monoliths on a nature show. The elders told me that soil makes the strongest bricks. We located one (providentially nearby), and I investigated. I loved this idea. The little critters choose the soil, sort it, clean it, and carry it to the surface for you! All you have to do is exhume it. It contains no stones or impurities because it is conveyed to the surface from deep beneath the ground one tiny termite mouthful at a time. Genius. And clean. The stuff is so tacky that a handful slung at the ceiling will easily stick.

The next challenge was simply lack of power. Everything has to be done by hand: hauling sand, cement, lime, charcoal (made by hand from hardwood), bricks, gravel (also made my hand!), water, and clay. Obviously these things are all heavy. And the oven is big, six feet across by eight feet tall, not counting the six-foot chimney. Mortar and concrete are mixed with a shovel. Hundreds of bricks are cut by hand. The charcoal is crushed with mallets. It all adds up to heaps of heavy work in the hot sun. I often begin at twilight in order to make progress before the heat of the day. Actually, every farmer in Africa does that. It just takes this white man a while to catch on.

The last challenge was the geometry. A dome of 250 bricks is no small feat. It takes a keen eye and careful hand. And again, I tried to keep it simple so that the young men can follow what I’m doing and don’t feel the need to have special tools or secret knowledge to pull it off. For the first six courses (rows of bricks) of the firebrick dome, we used a 24-inch measuring stick to maintain consistency in the distance from a nail placed in the center of the cooking floor to the inside face of the bricks—no measuring tape necessary. After that, the wall inclined too sharply to be built upon, unless you have twenty hands, so we filled the cavity with wet sand, sculpted it into a dome, and continued assembling upward and inward. I was quite proud of our six-sided carefully hewn keystone that clinched the construction. For me it echoes a sophisticated polygonal gemstone meant to adorn on a queen’s finger.

The project has become quite the local spectacle. Despite its private location, people stop by often to watch the progress, ask questions, and offer their hope that we will soon have good bread to eat. They are also delighted by the cleverness of both the sand dome and the radius-describing measuring stick. I invented neither contrivance, but I’m given credit anyway. People look at me strangely when I tell them I got those ideas from a book. They regard me even more strangely when I tell them that I’ve never done this before. 

After two weeks, I have a sunburned neck. My hands are a mess, between the pinches and nicks and caustic cement mix. But I’m happy. It has been wonderfully fun and pleasantly challenging. Today we finish the insulation and tomorrow we erect the chimney. On Monday I hope to clean the sand out of the dome—a dramatic step. Tuesday will be the first fire—small at first, to cure the oven slowly.

Someday I hope to get some pizza out of it. First we have to overcome the cheese obstacle. I tried negotiating for a milk goat today, so there’s hope. But long before that day, I plan to see some kids proudly baking, eating, and selling their own high quality bread.


  1. I love this! Such a neat project. I've actually asked Matthew to build me one of these before. :)

  2. He should do it. Actually, I will build one at my house, and you can use it. Will you make me pizza too? Please?

  3. Awesome!! Great project. My dad built one and uses it often. Perhaps we can enjoy them with you and Val :)

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  5. Wow, that is a pretty neat project! And to think that it is all for the learning of the kids, makes it a wonderful endeavor. Anyway, I hope thing are going well with the rest of the construction progress. I look forward to seeing its end result. Thanks for sharing

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