Hot From the Oven – updates on wood-fired ovens, Cob Ovens, Earth Ovens, Brick ovens…how to build them, how to use them

Once you’ve built an oven (or three), things start happening. Each oven is unique, and offers its own opportunities and lessons. You can learn something every time you use it, or every time you build a new one. Look here for questions, answers, and stories, not only from Kiko Denzer, who will be adding on to what’s in Build Your Own Earth Oven, but also from readers and other oven builders and pyromaniacs. Please do add your stories, recipes, questions, sources, and experiences.

Contents

Wood-fired earth ovens: experiments in DIY firebrick (aka “castable refractory”)

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I’ve been experimenting with cheap ways to improve lo-cost wood-fired earthen ovens. How can I make mud denser, harder, and more durable? Without going to bricks and/or spending a lotta dough? Adding sand to mud reduces shrink and increases density. But clay and sand are generally still less dense (hold less heat) than a good, hi-fired dense firebrick. Hmmm……

Experimental Goals:
1. to increase the density and toughness of a clay/sand thermal mix appropriate for building wood-fired ovens (and other wood-fired appliances?), 2. to fabricate a higher quality cast dome (“earth-oven”) style oven. Strategies: 1. adjust the mix of particle

Combining Earthen and Masonry Techniques in Wood-Fired Oven Construction

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Is it made of earth or brick?  This is a common distinction in the world of wood-fired ovens and comes with a whole slew of assumptions.  “Earth ovens are cheaper, easier to build but less durable.”  “Brick ovens are expensive, harder to build but more professional and will last longer.”  The oven build documented below is an exploration of the combination of these techniques to leverage the advantages of each.  We use earth where its sculptural quality allows us to perfectly mold it to the shape that we desire.  We use brick where it will give a good durable surface …

UK Earth Oven Project to help Bedouins

Here’s a new oven story that popped up one day via Google Alerts. It comes from the founder of The Makhad Trust, a UK non-profit focused on helping Bedouin tribal desert communities. It began with the planting of an acacia tree in the desert and continues, in part, by restoring the communal hearth — an earth oven. The back story, as published on their website, follows:

“Danny Shmulevitch, the founder, was walking along an ancient pilgrim route that runs through the Sinai Desert. He saw, sitting by the side of the path, a small girl wearing traditional Bedouin dress, who …

New Rocket Oven design by Flip and John

Jon and Flip Anderson have been working with Aprovecho Research Institute and building smokeless cookstoves in Haiti. They came up with this neat “rocket oven” design that answers some of the questions I get from folks about combining the dome oven design w/rocket technology. By simply using clay and organic matter and applying principles of mass and insulation they have created a beautiful, versatile, oven that can do significant baking w/very little fuel. For more about their work on developing business opportunities and helping with deforestation problems, goto www.RechoRoket.com. Here are a couple of their videos (they’re also working on …

Bluegoat Restaurant Oven, w/insulation-in-a-basket

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Here’s a little video showing the construction of a super-insulated restaurant oven. The “basket” design seems to be a pretty inexpensive and effective way to insulate — not necessary for every oven, but for ones that really get regular use, I think it’s worth it… It’s a pretty big oven, too, so I opted for hand-made mud bricks instead of mud over a sand-form. For more details about the technique (including brick-making, as well as photos of how well the insulation protects the bamboo), there’s an extensive post and pix about the Gathering Together Farm Oven, which was similarly (re)built.     …

Earth Oven variant: insulation in a basket over jumping bricks!

The earth oven at Gathering Together Farm's restaurant, Philomath, OR

Insulate! Insulate! Insulate! This oven gets used about 5 days a week, so it never cools down — partly thanks to 11″ of insulation under the hearth (vertical wine bottles in perlite), and about 8″ of loose perlite over the dome (poured into a basket made of bamboo covered in clay/plaster soaked burlap and mud). I built it for a local CSA farmstand restaurant (gathering together farm). The whole story (build and repair) follows, complete w/photos of making our own bricks and laying them up from the inside out!

The oven started in a public workshop; folks came to make …

Build Your Own Barrel Oven Book!

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Hand Print Press has published a new book about a hybrid style of wood-fired oven called a Barrel Oven!

Build Your Own Barrel Oven
A Guide for Making a Versatile, Efficient, and Easy to Use Wood-Fired Oven

The tools for a sustainable future continue to grow! In this book, Max and Eva Edleson offer a comprehensive guide for planning and building a practical, efficient and affordable wood-fired oven. The Barrel Oven offers surprising convenience because it is hot and ready to bake in within 15-20 minutes and is easy to maintain at a constant temperature.   It can be the seed …

Hawaiian School Garden oven

Mud ovens in Hawaii:

“These bricks, stacked and left to dry for about 2.5 weeks, are the start of a future earth oven at the campus’ Ulumau School Garden. The oven will be used by HPA (Hawaii Preparatory Academy) students, staff and their ohana to bake breads and pizzas, as well as to cook vegetables grown on site, said Koh Ming Wei, HPA’s sustainability curriculum facilitator.”

“HPA’s Hawaiian studies teacher Kuwalu Anakalea appreciated how the process included everyone’s mana. For her, the oven will serve more than tantalizing delectables. It cooks up a sense of community and value for building …

Cob oven ‘zine from Jorie Kennedy and Lizzy Rieke

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Below notes and gifts from Jorie Kennedy, who I met when she was apprenticing at the North American School of Natural Building, last year (2011). You don’t need a book to make an oven. Best is a friend who’s built one, but for friends she hasn’t met yet, Jorie put her oven love into this “hot-n-dirty oven lovin guide.”

Here are the notes she sent about it:

“My beautiful friend Lizzy (Rieke) and I (Jorie Kennedy) wrote this zine on how to make your own basic cob (earthen) oven.

“We dream of offering natural building, carpentry, and metal working skills …

Roberto Monge’s Oven Story

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Roberto Monge’s father – Alfredo Del Transito Monge Menjivar – grew up dirt poor in a jungle village in El Salvador, one of 8 surviving children in a family of 14. By good luck and hard work, he earned a law degree, found paying work, got married and started a family. I didn’t know him, but according to his son Roberto, the elder Monge felt indebted to his campesino roots; when he had to choose between a military dictatorship or a revolutionary people’s movement, he chose the latter, later assuming the position of Attorney General of the Poor in the …

Lily Gordon, 16, helps build ovens in Tanzania

David S. Cargo, who assembles info about community ovens for the St. Paul Bread Club sent me a link about Lily Gordon, a remarkable young woman, now 16, who has been helping villagers in Tanzania to build ovens so they can make their own bread (previously, bread had to be transported from so far that it would often be inedible when it arrived).

At the age of 11, Lily Gordon started raising funds for the village of Shirati, Tanzania. For her 11th birthday, instead of gifts, she asked her friends to bring money for the children of Shirati. The party …

Rainer Warzecha, sculptor, oven mason, collaborator, Germany

Rainer, working in Lübeck, 2009, building with a class of a secondary school students. "They were very enthusiastic and the whole process was a lot of fun. Especially the first fire in the oven made them jump around; it's always magic with the element of fire."

Some years ago now, I got an unexpected email from Elke Cole, a German-born architect now living in Canada, whom I had originally met at the first Natural Building Colloquium in Oregon, in the mid 90s. Elke was traveling in Germany, where she’d come across a public art project in a park in Berlin. It was full of earthen sculptures made by a German artist named Rainer Warzecha. At the time, I was collecting stories and photos to expand a little pamphlet about earthen art projects (Dig Your Hands in the Dirt). But most of what I had were …

Ian Miller, baker, oven builder, translator

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Ian’s Miller’s oven story (adapted from his translator’s note for the German edition of Build Your Own Earth Oven):

I saw my first earthen oven in Santa Cruz, California, where I was studying Agroecology. The fellow student who built it had a small bread business selling bread that he baked in it. My studies in Santa Cruz led to an internship on a biodynamic farm in Austria and there I got to know whole-grain sourdough bread and learned to bake it. I eventually learned that this bread was best out of a wood-fired oven but since I had never …

Ovens, builders, a new (oven) book for German readers

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Out of the blue one day I got a phone call from a guy named Ian Miller. He said he had built a few ovens, baked a fair amount of bread, was married to an Austrian and (among other things) interested in translating Build Your Own Earth Oven into German. With that began an adventure that is now resulting in a new (German!) edition of the book, published by Stocker Verlag, out of Austria (they also publish Austrian permaculturist Sepp Holzer, which makes it even more of an honor). Very interesting to let go of the book and let someone …

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New Community Oven in New Jersey

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HANDS stands for Housing and Neighborhood Development Services. They work out of Orange, New Jersey to try and reclaim dilapidated houses and other “eyesore properties,” and return them to the neighborhood as affordable homes and community assets. They also work with individual people and neighborhoods, and are creating an Arts District in a former industrial area called the Valley. A recent Google Alert brought in notice of a new community oven they built, and the following story from their quarterly report:

It started as a dream idea of our Executive Director, Pat Morrissy: “Let’s build a community outdoor, wood fired

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Video: clean & hot: how to light a fire in your oven

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How you prep and lay a fire makes a big difference to how things work — or not — in your oven (and other stoves). It’s really pretty simple: dry fuel, small sticks (plenty of surface area), plenty of space for fuel and oxygen to mix — and put your kindling on top, so the fire burns down, clean and hot, like a candle. The video here is a (pretty poor) attempt at sharing some pix of how I do it. It’s too long and wordy — a rough draft. I’ll try and get the next edition done soon! Meanwhile, …

Adjusting mass for optimal performance

Here’s a valuable perspective on the benefits of smaller, easier, cheaper, “faster-cooling” ovens, and a working baker’s comparison w/the classic Alan Scott brick oven design (which isn’t always the best option for someone who wants to start small and simple).

The baker is Noah Elbers, who runs a small bakery in New Hampshire. There are some nice photos of him and his oven(s) on the web, but he’s clearly spending his time in the bakery rather than on the computer — hurrah! He does participate in the brickoven group on yahoogroups, which is where this comment came from.

It is …

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Guest Article: An Earthen Oven Odyssey by Joe Kennedy

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I have been making earthen ovens for over twenty years now. I made my first one in 1991 when I was working with architect Nader Khalili at CalEarth in the Mojave Desert. We were making a lot of adobe bricks at the time (friendly Persian-sized ones – 8”x8”x2”) and also building domes of regular fired bricks. I’m not sure what got it into my brain to make an oven, probably an old picture of the ovens at Taos Pueblo. One day I made a round foundation of adobe bricks in a mud mortar bed right on the ground, then hammered …

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Terra Preta and “the Biochar Solution”

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The Biochar Solution: Carbon Farming and Climate Change, by Albert Bates
A review by Kiko Denzer

Living trees lock up carbon, and burning releases it. That’s the conflict-ridden equation of global warming. Albert Bates has been at the front lines of the warming conflict since his 1990 title, Climate in Crisis. In this book, he defines “biochar” as “charred (pyrolized) organic matter intended to be applied to soil in farming or gardening,” and argues that partial burning of waste wood and other carbonaceous matter can effectively “lock up” carbon and store it underground in a human-fired echo of what …

Alan Scott, Brick Ovens, A Marriage

Alan Scott (front) at work on an oven (photo courtesy Ovencrafters)

Alan Scott’s Ovencrafters provides DIY masonry oven plans and hardware (doors and pyrometers) for bakers wanting to start their own small business, or just to bake large amounts of bread and other food for family and friends. It was set up on Gandhian principles of “Policy with principles, commerce with morality, wealth through work, and science with humanity.” Many ovens and many small bakeries now feed good bread to their communities as a direct result, and the book Alan inspired and co-wrote, The Bread Builders, has become a bible for a growing circle of builder/bakers.

Alan, an Aussie who inadvertently …

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How Wide A Door?

This seems to be one of the bits of the book that could be improved in the next edition.

Yesterday, I got it again in this lovely note from a lady named June:

Hello Kiko:
I am a 68 year old woman making my first mud oven following the design in your book – I’m really excited about it, and have a question. Does the width of the door matter? A friend gave me a beautiful peel ahead of the oven and it is 16 inches wide. I am making a 27 inch oven and would like to know if

Kiko’s Recommended Oven Links

This is a somewhat random list of sites and sources of information — mostly free. It also bounces around between earthen and brick ovens, traditional and modern, simple and complex. If you have any recommendations, let me know!

— Kiko

The Masonry Heater Association’s oven page: A goldmine!
Le Four a pain de Jean-Marie: Mobile ovens ala Francaise
Brick oven plans: free from Forno Bravo (vendor of hi-end modular ovens)
“Nifty, easy-to-make (earth) oven”: the quick and dirty version, as printed in Mother Earth News in 02 (before I got really serious about insulation!)
Bread Ovens of Quebec: a classic …

Dan Wing on Trailers for Mobile Ovens

Dan Wing with his mobile (trailered) oven -- and bread

Much as I try to discourage them (see pp 98-101 of Build Your Own Earth Oven, 3d ed.), lots of people want to put their oven on a trailer and tow it long distances at high speed. Dan Wing, co-author of The Bread Builders and builder of fine gypsy trailers, as well as the maker of a well-travelled oven, kindly wrote up a thoughtful and practical set of notes on the safe and proper construction of hi-speed auto-trailers suitable for heavy ovens. It’s a downloadable word file that you can get by clicking here: Oven trailers. If you want to …

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Michael Pollan, a Cob Oven, & the NY Times

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“Communal table: A 36 Hour Dinner Party”

The NY Times Magazine recently published this article by Michael Pollan about a 36 hour dinner party cooked in a mud oven. Best, for me, was how he explained the purpose of the oven:

The idea is to make the most efficient use of precious firewood and to keep the heat (and the danger) of the cook fire some distance from everybody’s homes. But what appeals to me about the tradition is how the communal oven also becomes a focus for social life (“focus” is Latin for “hearth”), a place to gather and …

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Solstice, 2010: bring in the mud! (into the house, that is)

about 300 pounds of masonry moderates a small space

This time of year I don’t usually get too muddy, but I brought some mud into my office last month so I could have a better and more efficient source of heat — finally! This little “heater hat” effectively turned my little iron box stove into a mini-masonry heater — with an oven! (note the wooden door on the right, just above the iron stove door). The wood that used to over-heat me, briefly, in the morning, now keeps me comfortably warm all day, and into the next morning (depending on how long I fire it and how cold it …

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the upside down fire

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You can greatly improve how your oven performs by how you lay and manage the fire. Here’s how and why I build what Pat Manley calls “an upside down fire.” (Follow the link to an overlong video version). The first principle of fire requires applying to heat to fuel. When the fuel gets hot enough, it bursts into flame. But if you pile many pounds of wood on top of your kindling, it will take a long time before all your fuel can really start burning. Meanwhile, you’ll get a lot of smoke in your (and possibly your neighbors’) eyes, …

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Frequently Asked Oven Questions

If you can’t find an answer to your question here, in the book, or elsewhere on the site, please feel free to leave a question in the comment section and we’ll get back to you asap (please do scan the comments first, as you may well find your answer there).

Jump to: Efficiency, design, etc. | Using the oven | Materials & Construction | Foundations | Mud vs. Brick Efficiency, design, etc.

Q: How efficient are earthen ovens? A: There are two things to consider here. First, since you have to heat up the whole mass of a retained heat …

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ovens and efficiency

Dear Oven builders, mud teachers, bakers, and eaters:

I would like to talk to you about some of the claims being published about the efficiency of earthen ovens.

I think we need to be clear that any masonry oven, whether it’s made of unfired earth or fired brick, is not, by definition, a “fuel efficient appliance” — especially if it isn’t insulated.

There are more and less efficient ways to work with an oven, and some of them make quite good use of the wood burnt in them, but in my experience, those ways don’t apply to people who just …

Noah Elbers on earth vs brick ovens

Noah loading his current oven, a spanish Llopis with a revolving hearth!

Noah is a working baker, builder, and farmer who has built and used earthen ovens, a classic Alan Scott oven, and now a very fancy Spanish Llopis oven. Here he provides very clear and detailed data on the differences in fuel consumption and food production between earth and (massive) brick. In short, he explains exactly why an Alan Scott oven may not be the best option for a home- or small-scale baker.

Elbers owns and runs The Orchard Hill Bakery in New Hampshire. He participates in the brickoven group on yahoogroups, which is where this comment came from, but as …

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Oven dome height for different size ovens

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In the space of two days, I got two emails from people asking the exact same question. So here’s clarification, which I’ll have to include in the next printing! Thanks to those who wrote…

“Typical dome height” is 16” (p. 51). Some pizza ovens are lower because they’re used exclusively for pizza, which means they can have a low door without losing the 63% ratio of dome to door height — and they don’t have to worry about getting a turkey through the door.

The previous edition didn’t specify an ideal height, and in fact, a high domed oven will …

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new commercial oven at CSA farm

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Here’s a new commercial oven at Gathering Together Farm, a small farm/CSA restaurant in Philomath, Oregon, with cooks JC and Lisa posing with tools. This is a super-insulated design, with an external basket frame covered w/clay-slip-soaked burlap and insulating (sawdust-clay) plaster. When dry, the open cavity was filled w/loose perlite for insulation. The thermal layer is the standard clay/sand mix, covered with a cardboard expansion gap/thermal break (see the oven-fuel-firing-times-and-insulation post), and a layer of sawdust-clay insulation. Then about a 6″ space, and the final covered frame. The base is a stout metal box. Less well insulated ovens are typically …

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oven journal: details of fire & food

My oven journal, such as it is, follows. It includes how we went about preparing several big holiday meals, as well as other details that may be of interest if you’ve just built an oven and you’re not quite sure what to do with it. Or maybe it will all read like so much unintelligible shorthand. (If so, please accept apologies. I’ve posted a summary of what I learned as a separate item, under the title “oven fuel, firing times, & insulation.”)

Of course, once you realize that your oven will cook anything, the best inspiration will be in your …

oven fuel, firing times, and insulation

A couple of years ago, I decided to try and keep a bit better track of my oven’s performance. In particular, I was interested in seeing how much wood I was burning compared to how much bread and other cooking we were getting out of it. My data is neither consistent nor precise, but the exercise has been useful, if only as a good excuse to focus my attention on what I was seeing and doing.

I’ve posted my “oven journal” separately; it includes specifics of each oven firing, including how much fuel I used, how long I fired, what …

cob ovens on trailers

“I was wondering if you might have any info or resources for cob oven on trailers?”

This is without doubt THE most frequent inquiry I get. It’s also a large part of why I decided to put up a blog. So here’s my thoughts and experience, over and above what’s already in Build Your Own Earth Oven:

I wouldn’t try to put a cob or earthen oven on a trailer myself. I do know of one guy who did — he had to do repairs on the oven before the year was out — but I haven’t heard from him …

waterglass for binding earthen surfaces & pigment

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“Waterglass” for protection & paint

Waterglass has become my preferred binder in places where it’s needed. The chemical name is sodium or potassium silicate. It’s an inert mineral compound similar to window glass, but under heat and pressure, it’s soluble in water. I get it from a ceramic supplier for $9 a gallon. It’s clear, viscous, and pours like heavy cream. It dries into a clear, brittle substance that crushes to a fine powder, but it has significant binding power, and is used in some refractory cements, as well as numerous other industrial applications.

I’ve only discovered it in the …