Lorena Stove

The kitchen we replaced for Vielca and Yarelis

One of the most important things for us living on Ometepe is our community. We have built strong ties to our neighbors here and want to help them improve their living standards. At the same time, it important that we respect their culture and don’t try and impose our ideas on their lives. So Trevor and I have thought long and hard about ways we can help implement change here. We try primarily to lead by example. We have built our home out of locally available materials. However, while our home would not be considered lavish by Western standards, here it was seen as a monumental construction project considering many people live beneath one sheet of metal roofing with walls made out of black plastic.

We have spent many hours looking for a project we could use to introduce small scale natural building and struck upon the Lorena stove. The stove designed by Ianto Evans of the Cob Cottage Company in Oregon while he was working in Guatemala. Made out of cob, like our home, the materials to build it are readily available. Having been designed in Guatemala, the style of cooking is similar to that in Nicaragua. We found these factors, among others, make the idea easy for our neighbors to adopt.

There are many advantages to building a Lorena stove. The stove design is incredibly efficient, particularly as my neighbors currently only have a few bricks they use to support a pot over a burning log. In this stove there is a burn chamber to protect the fire from the wind. It has been demonstrated that this design can reduce the use of firewood by 50%. Given that Ometepe is a protected forest we hope that this can help slow the rates of deforestation here as it has in other areas where Lorena stoves have been adopted. Less wood used means less time chopping wood, decreased cook times mean less time spent preparing food. All of this leads to improved quality of life. But the most compelling feature is improved health with the addition of a chimney. While the stove will not be completely smoke free, a significant portion of the smoke will now exit the cooking area. This is particularly important for improving the health of women and children.

We also are including the local women in our build. We think it is important that they understand how the stove is built so they can maintain the stoves over time. It is also a wonderful opportunity to begin to train them on how to work with cob so they can see the advantages in implementing it in other aspects of their housing. We intend to make it a requirement for every stove we build that the woman of the house participate in the build. It also gives them valuable employment skills as the demand for cob increases in our area.


So, how do you build a Lorena stove you ask. Really it’s not that hard and doesn’t take that much time. Ideally, the entire stove would be built out of cob. However, for this stove we chose to start with a concrete block base. There were a couple of factors that lead to this decision. One factor was timing. A cob base must be fully dry before you begin to build the stove on top. Our timeline didn’t allow for this. In other projects you will see stoves built directly on the ground or even on a wooden table. For us, getting the community to accept the design was really important and people here love concrete. We decided with our neighbors the concrete base was the best option. We built a form out of concrete block and the filled the interior space with sand.


Concrete block base filled with sand

Leveling the sand before we add the cob mix

After having built our entire house with soil dug from our property we are quite familiar with the soil on our land. We dug from a clay rich deposit on our land a dried the clay in the sun. We then broke the clay into manageable pieces and ran the dry clay through screens to create a fine powder. We wanted all our materials as dry as possible so we could ultimately control the dampness of our mix.


Breaking the clay and sifting it

We decided on a ratio of one five gallon bucket of clay soil to three and half buckets of coarse sand. We mixed the dry ingredients first and then added the water. We mix with our feet- cob dancing. Get some friends over, turn the music up and have fun. I find the mixture with all the rocks sifted out the sand and clay is better for my feet than a pedicure.


Adding water to the dry clay and sand

Cob dancing

We used the plastic tarp to roll a cob burrito insuring the bottom gets mixed in well

Our aim was a dry, very sandy mix. We opted not to included straw in this mix because of the proximity to the fire. There are several ways to test if your mix is ready. I always listen for the sound of the sand rubbing against the sand. You should hear a crunchy sounds as you squeeze a ball of the material. We got a lot of laughs as we were listening to the dirt. You also can throw a ball of the material at a rock or a wall. It should stick with out falling and not crack too much. You want enough clay to coat each grain of sand but not too much. If you have too much clay in your mix then as it shrinks you will experience cracking, not enough clay and the mix won’t hold together well. A certain amount of cracking is to be expected during the drying process but too much cracking will endanger the structural integrity and the longevity of the stove.

We filled the last four inches of the space in the concrete form with cob to serve as the base for the fire. Above the concrete base we built a wood form for the stove. We set our form slightly inside the concrete base. That way if there is any settling the entire cob form will slide down into the space rather than sagging and cracking. We filled the form with our cob mix and compacted it down. You can get creative on how you compact the cob. We had people stomping it down with their feet.


Filling the concrete base with the first level of cob

Compacting with our feet

The form is full

We filled slightly higher than our form to have enough cob to cover the sides of the pots. The thermal mass of the cob will help retain the heat increasing the efficiency of the stove. We let the form sit over night to dry before we returned to carve the seats for the pots and the channels for the fire.

When day two arrived we were all anxious to take off the form and start carving. After we remove the form we marked out the spaces we needed to carve for fire and the pans. We opted for a design housing three burners and a 3 meter chimney. The first will be closest to the fire and therefore the hottest. It is also designed to house the biggest pot. The pots decrease in size and heat as you move away from the fire. The final hole we carved is where we placed our chimney. We purchased Vielca new stainless steel pans for her new stove. Ideally we would use cast iron but it is very difficult to find here. Aluminum is the most common. Trevor was concerned with problems leaving the aluminum close to the flame over time as the pans will stay in their seats to keep the burners closed off.

Removing the form
You can see the layers where the cob was compacted
Marking where the pots will sit

We carved inside our guide line to ensure a snug fit
Carving the burners

When carving we started inside our guidelines. This ensures that we will get a snug fit when we sit the pans inside. Dipping your tools in water regularly helps get smooth cuts and prevents material from sticking to your tools. Once we were close we sat the pots in the holes. We wet the outside of the pots to help them slide into the seats. By wiggling them around we were able to get the perfect fit. It’s also important to keep the seats level. Then within the seat we carved a smaller diameter circle down another inch to create a space for the flame to spread out beneath the pan. This allows the flame to spread out over the bottom of the pan.


Seat for the pot and channel

You also need to carve out your burn chamber. Again, start inside your guidelines to make sure it doesn’t grow too large. You will need to ensure you have enough cob between the top of your burn chamber and the bottom of the pot so the structure doesn’t collapse under the weight of a full pot. We left four inches. The burn chamber is a 6 inch diameter half circle. We used a string and two nails to score the guideline. Dig back far enough so that the fire will burn directly beneath the first burner.

Guideline for the burn chamber

Once you have your seats and the start of your burn chamber it is time to carve the channels. It can be a bit tricky carving out the channels between each burner. Someone with long arms and small hands is the person you are looking for. We began by carving a hole in the center of each burner about the size of your hand holding an egg. Spoons are the best tool for this job, think about tunneling in a sand castle. You dig down about four inches heading toward the other burner. You are aiming to create a smooth curve that leaves enough structural integrity that the weight of the pots don’t cause a collapse. As you begin this process you will get a feel for how much material needs to remain above you. It is also important to avoid hard corners as these interfere with the draw of the fire. You want to be working from both sides simultaneously to create the connection. It is an exciting moment when your fingers create contact!

We started by connecting the first burner directly above the burn chamber. Then we channeled over to the second burner. For the second and third burners you must do a little more shaping to control the flame. You want to create a “speed bump” to drive the flame channel back up towards the bottom of the pot. Without this, the flame would pass too far beneath the pot to heat it. Using the mixture that had been removed by our tunneling we built up the baffles. It should look like the photo below.

Baffle. Notice how it resembles the valves in a combustion motor.

We began the chimney exit by connecting the third burner to the chimney seat. This is a little different than your other channels. Our chimney is 5 inches in diameter so we dug a five inch seat for the chimney straight down for four inches. Then we narrowed the diameter of the hole by an inch to create a seat for the tube to sit on. We continued to dig straight down until we connected with the channel from the third burner. The channel from the burner is carved with the same smooth curve as the other channels. One we made contact we continued the straight chimney channel down an additional four inches. This space serves as the ash trap. It will need to be cleaned periodically.

In addition to carving all the channels, we ensured all the surfaces were level. This included the seats for the pots and the top surface. We also smoothed the inside of all the burn channels. To all for the use of larger pots or comals and to help prevent chipping we added a chamfered edge to all the burners.

Ideally at this point you would leave the outer surface rough to aid in drying and minimize surface cracking. Given the scope of our project we chose to burnish the stove to provide a more finished product at the end of our build. We felt this was important for community acceptance. Some cracking is expected to occur over the one to two week drying time before we fire the stove for the first time. We will use this as an opportunity to teach our neighbors how they can fill cracks and maintain their stoves over time. This is particularly important if the idea grows in the community and people begin building on own their stoves with a less than perfect mix.

We have an astounding response to our first stove build both from the community here on Ometepe and our friends and supporters who follow us online. We are excited to have completed the first step in our larger journey towards increased education on living more healthy and sustainably. We look forward to being able to spread the knowledge and reduce the building costs of the stove to make them more accessible to everyone. Please continue to follow us as we share the first burn and plan for our next community development project in April 2019.

For more information on how you can join us please visit www.eljardinometepe.com

For more information on how you can donate to help support our project please visit https://www.gofundme.com/help-build-clean-stoves-on-isla-de-ometepe?pc=ot_co_dashboard_a&rcid=3f6f4c57e2374e7abbd9ad2de804bbcf

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