Thursday, August 14, 2008

wheat harvest

boys, their cousins (and Uncle) from England all helping -- for a few minutes, at least. Won't know yields until I get the grain threshed and winnowed. It looks better than the past few efforts, but still not the 300 pounds I was aiming for when I fenced off the 3,000 sq. ft.

performance data on cob/clay ovens

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. Copied here w/his permission...

-- Kiko Denzer

Re: Thermal Mass
Posted by: "noah elbers" breadwks AT
Thu Jun 26, 2008 4:40 pm (PDT)

When I was just starting out commercially I baked in a minimally insulated, 4-5" thick cob/clay oven. Here was my schedule and quantities just to give you an idea. This was a 5 foot deep oven, 3 ' wide app. but scaling up or down does not affect the number of loads much at all.

I would fire the oven from cold at 4:30 am. With three stokings (a brisk fire most of the time) the oven was fully saturated by 10:30 am.

2 loads of pizza (6 each load)
3 loads of bread (30-36 loaves each load)
2 loads of cookies or bars (totaling 150 pieces) sometimes pies, but not always, up to 15 on a regular basis, but over 100 at thanksgiving and christmas.
25 lbs of granola
overnight beans
By the end of the next day the oven had cooled enough to dry fruit like apples and plums, or herbs and tomatoes from the garden. Three days after sweep out the oven would be back to air temp.

Light up was very easy in this oven even from cool temps since it heated so fast, wood quantity was miniscule compared to my later AS design, and baking quality when I was within it's production capacity was better I feel.

When I built the AS oven, a 4X6, I routinely baked upwards of 700 lbs of dough on a single firing, (500 loaves) and a few times over 1000 lbs of food (bread plus wedding catering). Those things when properly heated can really hold on to some heat, but until they are nice and soaked with heat (something I didn't fully appreciate until after two years of baking in it) I don't think they bake very well.

When I retired my AS it took well over a month for it to come back to room temp. Amazing, but not useful for home bakers. The other downside of the AS design for home use I think is that once the thing is fully heated, you either need to wait a long time before it enters the lower temp zones better for more delicate things, or you need to have huge amounts of food to bake. The low mass oven will drop lazily but steadily once it is up to full heat, and in a matter of hours you can go from great pizza to great lemon meringue pie. Half an hour at pizza temp, 2 hours in the bread zone, 5 hours for cookies and desserts, 12 hours for braising and roasting, 24 hours for drying etc.

I have no agenda here, just ten years of small scale commercial baking experience that spans three ovens now. I was basically a home baker when I started, the business grew and required greater baking capacity, and I now no longer bake in a black oven. I think retained heat baking is fascinating, rewarding, and generally as good as any other cooking method. My motive in going on and on about this is to help people who have not baked with retained heat understand some of the heat dynamics of different thermal materials. Saving on costs, fuel, air pollution are tangential for me. The experience of using the oven is what I care about most, and I share this from my experience with the two types of ovens. (now three, but the Llopis is a whole different animal)

Noah Elbers
Orchard Hill Breadworks
breadwks AT
East Alstead NH 03602
(603) 835 7845

Sunday, July 20, 2008

more images of recent sculpture

more images of sculpture:
The reddish leaf pattern is one of a pair of relief pieces in earthen plaster, which were done to decorate side panels on one of the performance stages at the Kerrville folk festival in Kerrville, Texas. It was a shared project that came out of a decorative plasters workshop at the Texas Natural Building Colloquium — many folks took part, all drew up various ideas, and the group chose this pattern, which is one I’ve been working and re-working in various materials and various settings for several years. This is the biggest!

Friday, July 18, 2008

recent sculpture

The tall cedar piece I just finished for a friend who had experimented with growing wheat; she asked for a vertical sculpture to fit a space in front of her house. All the grasses were just coming up when I started, so my model was a very early stage of growth when the first leaves are just unfurling. I started w/out drawings, which meant that when I needed a second look, the grasses had advanced to a completely different stage, and I had to work from memory and imagination. The piece of cedar was probably cut from an old snag by a local homesteader, sometime in the early 1900s, and split into a post that held up a barn. When the homesteader’s grandson repaired the barn, he took a couple of old posts out, and I got lucky. There was an old square nail embedded in the wood, which shows up about 1/3 of the way up, as a dark bruise and a scar. I finished it with a torch and oil.

Wednesday, July 9, 2008

Oven dome height for different size ovens

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 work — the traditional southwestern horno is typically quite high. In general, however, for bread ovens you don’t want to increase oven volume any more than you have to, as it reduces the concentration of steam — and steam is what causes the formation of an ideal crust. In addition, your door would have to get higher and higher in order to maintain the 63% ratio.

If you make a really large oven, it gets much trickier maintaining the right curvature of the dome to keep it from falling in (“large” might be 10 feet wide or more...). But otherwise, I use 16” as a standard height for 22”, 27”, 36”, and larger ovens. The largest I’ve built was 4 feet across, with a 16” dome.

At that size, I was very careful to make sure that the shape of the dome was truly catenary. In fact, I made a template by hanging a loop of heavy cord so that the ends were 48” apart, and the center hung down 16”. I traced the line, cut it out, and used the template to shape the sand form so that I would be sure of the strength of the dome.

The little pic is a postcard of a typical Southwestern horno — clearly more than 16” high inside the dome.

Monday, June 23, 2008

oven ready to light

Here's a fire laid and ready to light: sticks stacked log-cabin style, w/lots of open space and air around them for good combustion, and a small teepee of fine kindling at the front, waiting for a match. Another reason I like oven-dried wood is that I don't need paper to start a fire -- just fine slivers of wood and, poof! a bright fire. In the bottom photo, you can see the clear path that inflowing air takes down the center-right side of the hearth floor, where there are no obstructions to create turbulence. 

Tuesday, June 17, 2008

new commercial oven at CSA farm

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 barely warm on the outside after hours of firing, so I'm expecting this one to hold its heat really well. But so far it's only had drying and test fires, and doesn't even have a baking door! Mason Trevor Norland is going to fashion stone feet and skin for the lower portion of the base.

Monday, May 5, 2008

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 garden, pantry, farmer’s market, or grocery store.


32 lbs of oven-dried wood, mostly small split fir, two larger (3-4”) chunx of ash forming bottom channel, one 3” chunk of oak across the top, all under small fir. Looks like insulation job might be pretty much dry by now.
1:45: went out to light the fire
2:45 or before: already going white
Well, Hannah suddenly realized the bread was over-proofed, so I took out the (newly stoked) fire, browned stew meat, cooked pitas, and then she said it would be better to re-form the loaves for a second rise after all. So I re-loaded the fire and added more fuel. Turned out to be a good thing, because I think the oven wasn’t as hot as we need, due to firing sample bricks for CA workshop. So now it’s all going again. Burnt just about the whole load of wood. Not necessary, but didn’t want oven to cool down that much.
When the bread was ready again, oven was too hot. Put in a large pan of water for ten minutes. Bread was perfect. Then pies, stew, heated gallon of milk to 160 or so, then it was time to make meringues.
10-30 or so, took out last batch of meringues, oven at about 250; still seems to be losing heat too quick. Loaded her up with wood.

Re-insulated the oven last weekend, with friends. Discovered not that a critter had gotten in, but that I had insulated the oven with about 1.5” of sawdust clay, and approx. 6-8” of straw-clay. The latter had burnt completely out, leaving nothing but ash and a very fragile (but impressively solid) layer of insulating firebrick w/not a speck of sawdust left in it. So we insulated with pure sawdust clay (I think I must have been short of sawdust last time, and rich in straw), and didn’t plaster it. Midweek, for Isaac’s 4th bday, we made pita bread. After feeding the ravening hordes of boys, I left the oven to burn down and didn’t think to close it, much less dry wood, ‘til hours later when everyone had gone home. So I loaded it with partially damp fir and closed it up. It was still 150° the next day. Dried (and still warm three days later), the fir weighs 28 pounds, and makes a pretty full barrow load. I’m not expecting to burn all of it. I left about 5 pieces unsplit, about 3x3” each, stacked them tinker-toy style, and set tinder ready for lighting.
Hannah lit the fire approx
1-1:15, I got back from cutting firewood at about 1:30 and it was burning without smoke, a flaming path under the stack of larger stix clear to the back.
1:45, about 1/2 hour in, the oven was already burnt clean down to the hearth bricks and 3/4 of the way up to the front
2:15: 3d stoking, 4-6 small sticks (3/4” sq.), to keep the smoke down and the flames bright, clean now all the way to the front.
2:35: down to coals, added 9-10 sticks, same size
probably about 2:45 or so, Hannah went for a walk and asked me to brown the meat for a stew. So I kept tossing in a few sticks every 15 minutes or so while I made lamb meatballs, browned elk stew meat in a cast iron pot in the oven – very hot – cut up onions, etc. When Hannah got back the stew was up to a boil in the oven – transferred it to the stove to simmer.
4:20: cleaned and soaked; Hannah rolled out about ten pita; they cooked fast.
4:45: 8-count in the oven, floor hot – flour went black in under 5 seconds; loaded first batch of ten loaves.
5:20: second batch in (3 loaves), first batch was perfect. Abt. Ten minutes later, a big batch of cut up veg go in
5:55: second bread out, internal dough temp just a bit over 200°.

1:30, started fire w/oven dried grape and apple prunings on a base of larger chunks of maple & the like; haven’t had time to re-do the insulation, but looked into the hole a bit further: looks big enough for a whole family of packrats! I hope they’re not heading for the house, or already into the heated bench…
2:24: mostly clean, large chunx still making large flames
3:58, 1st load of ten loaves in, after pita bread and about 1/2 hr soak. Burnt up the whole load of faggot wood, plus the chunx. Starting with the large wood and some small stuff to get it going seemed like a good way to go. I had a nice bright burn for the first hour w/minimal re-stoking, then I did several small stokes, just a handful of twigs at a time, while I was harvesting and washing dandelion root (for tea, which I hope to dry and roast in the oven later).
4:35: two apple tarts in, following the last four loaves. First ten came out perfect after 1/2 hr.
7 pm: the lack of insulation makes things cool off way faster. Had to restoke for pizza anyway, but the pies wouldn’t have cooked without the extra time at higher heat which pizza made possible. Then a pot of beans and a pot of squash for potluck tomorrow.

5:45 pm: started fire w/oven dried fruit prunings and various big chunx o’cherry, maple, etc. wet day, cool house,
6:15: top front was burnt clean, re-stoked w/lots of small stuff
6:29: clean down to about 6” above the floor, most of the faggot wood gone, added more larger stuff
7:08: all clean, added more big stuff
8 ish: added a small number of small fir sticks to goose things
8:30-ish, rolled pita and cooked it
9:00: first batch of bread in, oven hot, 9 loaves, internal dough temp over 200° by 9:35
9:35: second batch in, cinnamon rolls waiting

first firing since sending the new edition off to the printer; everything came out beautiful! Pita, two perfect batches of bread, (14 loaves, 25 lbs), stoved taters, elk stew w/snips & carrots, 2 ginger cakes, pot o’ beans, rice pud, 2 trays of bread crumbs/cereal, and wood to dry. Long soak (1/2 – 3/4 hr), about normal firing times, a bit more than usual wood because we didn’t have anything but big gnarly chunx. Still haven’t looked into the hole in the insulation…

1:45: started fire w/oven-dried grape prunings and assorted big chunx of maple and holly; some cherry too. Oven hadn’t been filled up full enough (hard to get prunings in there!) Tended fire for 15 minutes or so, splitting stuff up, feeding it, etc.
2:30: still sooty around lower edges, otherwise mostly clean, down to coals (Hannah had to come in and remind me to check it!)
-- two stokes --
3:45-ish: flames just about gone; spread out coals, went inside to roll out pitas
4-ish: cooked pitas, set metal against door to soak it
4:15: too hot! About a 6-count, flour went black in less than 5
4:40: loaded 9 of 14 loaves
5:25: second batch of bread in, w/one tray of ‘taters and one tray of sliced delicata squash
oven turned out not to be so hot as I’d thought upon first temp test. Maybe because much of the wood was in bigger chunx than normal? (Pieces were too big and knotty to split down easily, and I was too much inside to stay on top of frequent stokes). Hmmm. But. We got the two batches of bread perfectly cooked, one darker and one lighter, as well as two poppyseed cakes, two ginger cakes, ‘taters, squash, and wood for the next fire.

12/22/06: hannah wants deep heat for extra baking: cakes, cookies, etc. for xmas
11-ish, started a fire w/small split oven-dried wood, and two large gnarly chunks. Added one small batch of small split stix.
1 pm, Oven burnt clean, added another few small sticks. Big chunx still burning.
1:50: added last half of a big chunk, and 2 other small stix
3:20-ish: loaded loaves after doing a batch of pita breads, after running around to get a cloth to cover the table so we could take pix maybe for the cover of the new book. Uh-oh, oven might not be hot enough.
Lost track – but the oven was underfired for multiple bakes; 2d batch of bread came out OK, but we needed 375 for cookies, and didn’t have it. Burnt up the last of the dried, split wood for that, and all was fine. Loaded it up w/wood for next firing, called it quits.

12:47: fire started, no oven-dried wood, it got away from me last time, Coenraad & Courtney & kids coming to visit, regular load of bread, beans, bread pud, etc.
1:17: down to coals and smoke; another small stoke of small (2-3 finger wide sticks) on top of two large, gnarly chunks making a channel to the back of the oven.
1:30-1:40-ish: burnt clean in front, rearranged things to the rear, added more small sticks, big ones still solid
3:50: bread in, after pita, walk, visit w/C&C, who arrived just after walk
bread cooked nicely, two batches, but the temps were lower than usual, cooked bread pud and beans after bread, as well as a big pot of parsnips and leeks for supper. Put wood in to dry that evening, oven down to 125 in the am. Power of dry wood?

35.5 lbs wood, mostly maple, some locust and walnut, dried down to 32.5 lbs (8-9% weight reduction, approx 45 oz water, or 5.5 cups)
12:30, started fire of very small split stuff (finger thick), two small starter stokes while I split wood, then one regular stoke
1:10, almost burnt clean, restoked
1:35, clean, down to coals, spread coals and threw on three more sticks, going to roll pita
1:47, pita cooked, oven floor too hot for bread, used 16 lbs of fuel, quite a bit of coals left, but the bread is ready to go. Saving coals for steak & ‘taters later.
1:53, floor already cooled some, impatient, put bread in (3 loaves, 1/2 white flour, testing bread chapter, and testing a short firing)
2:10, bread almost done, one in back noticeably more done than others, worth noting that short fire makes more uneven temps at surface
2:15-2:20, bread done, one loaf needed a little extra time
2:32, oven at 350, put in large pan of leeks
ended by re-lighting a small fire and broiling steak from Donnie and Frieda. Will ask Hannah to check temperature tomorrow am.

11/23/06, tukkey day
7:30: loaded the warm (200 or so) oven with wood, which I should have done last night, but figured it was still worth doing even if only for a couple of hours
9:30: fair bit of steam came out of the oven when I opened it to take out the drying wood; it felt warm and damp. Seasoned firewood. Amazing. Fired it up, forgot to split it very fine until the second stoking.
Plan was to have the oven up to about 400 by noon, so we could load the 15 lb half turkey that Steve and Sallie raised. We figured a half bird would go faster than a whole one, so we could have it done by 3.
The rest of the day is a bit of a blur. 6 adults, 3 boys, one baby, and a morning visit from a neighbor, plus all the prep, meant I didn’t record all the details. That said, the oven was way too hot at noon ‘cause I hadn’t been paying attention to the clock and stoked one too many times. We should have cooked the leeks and parsnips immediately to cool the oven. As it was, we waited so long we had to separate the leg from the breast and cook ‘em separate. But that worked fine too. Leg cooked faster, but when it was done we needed more heat for pies, so we goosed the oven with one or two small fires. Then it was up over 550, so we had to cool it down a bit with a pan of water on the hearth. Four pies? Five pies? 2 squash, one apple, one gooseberry, plus a pear tart. Why so many pies? The hardest part of organizing this firing was the fact that so many different cooks were bringing so many different dishes. Now the soup is in the oven and it’s time for bed.

11/22/06, getting ready for tukkey day
4:35 or 4:40 or so, started fire w/what had been oven-dried wood left over from the previous firing; even covered as it was, I imagine it picked up several % moisture in the last week of rain. Oh well.
5:20: second stoke
5:50: burnt completely clean before I got out there (distracted, working on book), stoked a third time.
7:25 or so: down to just a few coals; had left firing door on too long while I put Isaac to bed, I think the oven got too much cooling currents; scuffled, cooked pita, they were slow. Soaked it a few minutes w/tin covering door, to see if temp would bounce back. Got an easy 10 count, floor not over-hot.
7:45: loaded 8 loaves
8:25: first loaves out, (internal dough temp just over 200°, oven at 350°), 2d load of 3 loaves in, plus tart in a few more minutes; wet wood? Too long w/just coals? Hmmm

11/15/06, mild, partly cloudy
4:50 pm or so, started fire. A couple of big knotty chunks, plus some small locust.
5:30: yow, oven burnt practically clean (no soot).
6:15, pita bread, so Isaac could have his favorite snack before bed
6:55: cleaned and scuffled
7:21: 6-8 count by hand, but floor burnt flour in less than 10 count
7:35: 8 count by hand, flour on floor browned nice and slow (still not black at 20 count)
7:41: bread in, 6 loaves
8:11: bread out, internal dough temp just over 200°
8:15: 400°, bread crumbs in
8:24: tray of crumbs brown, deeper pan still cooking (also in front of oven)
10:20: german poppyseed cake out, rice pudding starting to brown, covered it w/foil, temp at 300° (need to get a new one, not sure this one is accurate).
11:45: rice pud out, nicely browned (had to put it back in at 11 cause the foil had kept it from browning. Still half a load of wood left over. Temp at 250°+.

11/10/06, rainy! Not too cold (50s?) Hannah had xtra big batch of 30 lbs of dough; 6 extra for Abril’s wedding.
2:15, started fire, all dense, oven-dried aromatic, Port Orford Cedar (from Keith's tree)
3:15, hungry! Nothing since bfast. Cooked pitas right away, then T-bone steaks from Frieda, 3 mins/side (counted off in my head), could have been just a bit quicker, as the hearth floor did quite a bit of cooking. Started a pan of Millie's eggplant w/onions, garlic, & peppers with the steaks, but they were in front, and needed a good 15 or 20 minutes anyway. That back corner was hot!
3:40 spread out the coals and re-stoked twice
5:15 or so, Hannah knocked back the loaves and I re-stoked with about 4 or 5 very thin stix of maple (didn't use all the cedar that had been oven-dried)
6:05 scuffled the oven. OOPS! I forgot to do the simple arm test for temperature, and burnt the bread because of it. My mind was at work on the new edition of the oven book…
6:30, loaded first batch of 9 loaves
7:00: moved loaves to front (very dark in back, still at 140°)
7:10, internal dough temp at 200°, dark! Put thermometer in oven
7:20, oven at 500°! Hannah bummed, Kiko guilt ridden. But flour on floor browned instead of going black. Wait. Hannah put large pan of water in oven to cool it down. Said it wasn't in more than ten minutes, but she might have misread the thermometer, which she thought said still well over 500.
8:05: Kiko removes water, loads loaves, temp bouncing back, around 375°-400°
8:40 or so, most of bread done, save for 3.5lb loaf, which needed another few minutes to get up to 190°,
8:50 or so, last pie shells in, three full pies already cooking
9:30 or after: pot o' beans
8 am next morning, or so, beans had cooked dry, only the bottom layer burnt, oven still at 250. Filled it w/wood two hours later, temp read 225.

October, 30, 2006
2:15: started fire
4:15: fire down to coals, which Hannah had spread. Kiko scuffled and cooked about 6 pitas
4:30: loaded loaves
5:10 or so: 1st batch of bread out (about 8-9 loaves, nice and dark)
5:15: loaded 2nd batch of bread (3 loaves) and pie (oven at 350-400)
5:45: small bread rolls out, bread out later, much less dark, but done
7:15: bread Pud out
8: applesauce in (15 qts; temp was 250)
9:15: sauce out (225)
9:20: wood in
8 am next morning: 125, ambient temp overnight was low 20s.

another small batch of bread (6 loaves) to take us through to next bake day. Started small fire around 3 or 4 w/cedar and locust scrap that had been dried; it burnt clean after first batch of twigs went down to coals, kept adding a few more bits of wood 'cause bread was slow. Bread made w/higher protein white flour and some rye (about 10%); made for tougher bread, but nice air holes. Needed bread for lunch so Hannah made flat breads w/Isaac on the stove; we ate 'em w/fresh salsa verde and outrageous Brandywines -- and a bit of cheddar.
1. Oven hot, threw in more eggplant from Millie and Dave in front corners (cooler), but then added more stix, so they charred on the outside. Cooked soft through in about 5-10 minutes. Cleaned oven, then cooked
2. 4 pita breads, ate 'em for supper w/Isaac, more salsa verde and toms
3. cooked six loaves, didn't think the oven was that hot, but they were done in 20 minutes (in fact, overdone, temps were well over 200°); then:
4. Moussaka, ricotta custard (ricotta, milk, eggs (whites whipped), sugar, vanilla, madeira), apple crisp, pot of beans, squash, pumpkin seeds, milk for yogurt.
5. Took milk out (it was 180°), at about 10:15 pm, wrapped it up in big pillows overnight. It was still 110° next morning, goosed it up to 120° on the stove, added a tablespoon of old yogurt, poured it into a gallon glass jar and set it back in the pillows to yog. (Done when we came back from town about 2 or 3 pm.
6. Oven still at 200° next morning when I went to remove pumpkin seeds and eggshells; I meant to fill it w/wood for the next time, but got sidetracked. Finally, about 2 or 3 pm (24 hours after lighting the fire) I opened the oven and
7. Filled it with wood. It was at 150°.

small batch of bread (low on flour), but eggplant and peppers from Millie and Dave: Hannah wanting to make eggplant parmesan -- for the first time! Fire going hot and fast by 8:30 am; intermission later to burn up some charcoal left in the ash bucket. Rather than frying the eggplant, we'll roast it hot in the oven. Keep the kitchen cooler on a warm late september day. Hannah's folks visiting from UK; Sidney likes cake, but no flour! Raisins in the bread (soaked/boiled in strong tea first). Flapjacks (butter, brown sugar, soaked raisins (left over from raisin bread), oats, and whatever else seems good, maybe nuts & seeds). A large pile of egg shells to dry. Just stacked winter's wood, separating out the oven stix: twisty twigs of locust that won't work in the rocket stove. Soak water from raisins sitting in a cup. Too strong and acid for tea (makes the milk curdle). Maybe we'll try a rice pud w/raisin/tea water and yogurt instead of milk?
8. Oven very hot for cooking eggplant, so they were a bit browner than the cook really wanted 'em, but soft through. Better to have 'em a bit thicker than thinner at such high heat.
9. Pita bread for lunch
10. About 11 am? First batch of bread nicely dark in about 35 minutes,
11. pies in next, w/raisin bread (in front/cooler section), at just over 400. 1/2 hr. tart, 1 hr deep dish pie, then
12. taters and eggplant parm.
13. Rice pud set to boil at about 350, didn't quite get to a boil before we left for a walk, so added yogurt and put it in a bain marie. Took it out, nice and brown, at 10:30 pm, oven still well over 200. (bad experiment, might have been better w/egg in)
14. Put wood in oven to dry.

3/18/06: dry, sunny, a bit chilly
about five: started fire w/load of 2x4s split in 3ds, stacked very open; oven burned clean after 2d stoke, in about an hour
loaded 3d stoke, burned down to almost no coals,
bread wasn’t ready so I loaded one more small load of 2x4s, unsplit, not oven-dried.
After 1/2 hour soak oven still way too hot: loaded pan of water; after another 20 mins or so put in one loaf as test

2/11/06: dry, sunny, t-shirt weather
about noon: started fire
3 stokes, each one small, total amt. abt. 1/2 filled the oven; mostly fir 2x4 offcuts, a few sticks of alder, all pre-dried from previous firing.
2:45: loaded first bread
3:05: first bread done (8 loaves sourdough white)

1/16/06: rainey and wet, ambient temp approx 50, front of oven wet
1 pm, fired approx 2 loads of wood (oven dried);
5 pm, (approx), down to coals, scuffled, baked pita, bread (12 loaves)
6 pm (approx) both batches of bread out
? pm (just after bread?): put in two big pots of chicken stew (1 hot 1 cold?),
10:30 pm: just shy of 300° (unloaded one pot of stew, topped up the other one with water, put it back in – both pots were bubbling).
8:30 AM: just over 250

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 we cooked, and how long the oven held the temps, but being as I was always doing several other things on bake day, the records didn’t have enough hard data to be useful in any scientific way. However, I did learn some things, which I’ll try to summarize here, with some anecdotal information which I hope might be useful.

Four things stand out:
1. The effect on fuel/firing cycles of water content and weight (density) of fuel.
2. The value of insulation, and the various insulating properties of different materials
3. The effect of multiple firings on do-it-yourself, hi-temp insulation materials, and
4. An idea for further limiting conductive heat loss by including a “thermal break” between the dense masonry and the insulation

1. FUEL: Weighing my wood before and after drying it out in the final heat of the oven allowed me to compute how much water I was able to drive out of a load of wood. One 35lb load of “seasoned” firewood came out of the oven 9% lighter than it went in. That means it lost 45 ounces of water – nearly a quart and a half! Imagine how long it would take to mist that much water into your burning oven fire, and how much it would cool off and slow down the fire.
2. FIRING TIME: How long you fire the oven makes a big difference in how long it holds heat. Every half hour is significant. Related to this is the fact that the weight, or density of the wood is what determines how much heat you get out of it. A small pile of dense oak will burn longer and put more heat in your oven than a big pile of soft pine or cedar (assuming they’re both dry dry dry).
3. INSULATION: When I started paying more attention and taking notes, I would frequently end up with temps of 250 almost 24 hours after starting a fire. Then I started to notice that my oven didn’t seem to be holding heat so well. One day I noticed a small plume of smoke or steam rising from the back of the oven. There was a hole! “Aha!” I thought. “A critter has been making a nest in the warm insulation. I’m going to have to fill some holes.” When I finally got around to it, however, what I found was not a critter in my oven, but insulation that had burnt to ash and collapsed – completely.
This particular iteration of the oven (it has gone through more re-designs and rebuilds than I care to mention) was insulated with about 1-1/2 inches of “sawdust-clay,” followed by about 6” of “straw-clay.” Both materials are simply made of straw or sawdust mixed with clay slip (your clayey subsoil thoroughly crushed and mixed with water to a viscous liquid (thicker or thinner according to your preference). Straw-clay, being made of larger, springier stuff, is typically open and loose – great insulation, until the straw went from carbon to ash. Without enough clay to form a rigid connecting “foam” structure, the ash collapsed, and I lost insulation value. The layer below, however, of sawdust mixed with a higher proportion of clay, burnt out to a soft but rigid layer of fired clay-foam.
I repaired it with pure sawdust and clay, thinking it would last longer and insulate well enough. However, the oven did NOT hold heat as well as it had previously. Since I wasn’t prepared to replace the newly replaced insulation and plaster, I just had to swallow my pride in the oven’s performance and continue. However, performance HAS IMPROVED over time! Greatly. Clearly, repeated firings have caused more and more of the sawdust to burn out, so the insulation is getting lighter and more insulative.
4. THERMAL BREAK: Since the insulation is tightly packed against the hot masonry, however, it occurs to me that it would make sense to design in a non-conductive air gap between the dense masonry and the light insulation. Since doing the journal, I’ve tried this idea on several new ovens, using a layer of cardboard or paper machier, which will burn out and leave a void. But they were ovens I built for other folks, so I don’t yet have info about performance (my own or anyone else’s). When I do, I’ll post it.

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 since, so don’t know the whole story of his oven. Maybe it's doing just fine. It's hard to imagine that unfired earth would be able to withstand prolonged exposure to road vibration without serious cracking and ultimate failures.

The only oven I did put on a trailer was made of lightweight, hi-temp cement, as described in the book. I’ll refer you to that and Dan Wing’s article about trailers for ovens, which is on

Other than Peter Schumann's site-built, stacked-brick ovens, which I only know by the reputation of his bread and puppet theater, I haven't heard from anyone who has really tried to make simple, site-built temporary, wood-fired, masonry ovens. I've seen one in Mexico, mortared with mud so that it could be taken apart and moved to another town for another festival.

There are myriad other ways a person might build a quick oven, from simple (stacked bricks) to complicated (pre-cast, fitted pieces of fired clay (or hi-temp refractory cement) that could be constructed into a shell over a brick hearth). I would think that just about any one of these options would be much cheaper than building a road-worthy (and safe) trailer.

I'd love to hear from folks who've got experience they'd like to share on this one, especially anyone with photos of Mexican festival ovens.

waterglass for binding earthen surfaces & pigment

“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 past few years, so I’m still learning, but it has made murals possible in less protected areas where I might not have risked it before. It does interesting things with color. And it’s cheap!

Mixed at least 50:50 with water and sprayed (or brushed) onto dry mud and allowed to dry again slowly, waterglass will bind the mud to a significant depth, preventing damage from rain, hoses, and curious fingers (but not hostile ones). Brushed on, it soaks in deeper, binds more, and may darken colors.

Mixed with pigment, it produces wonderfully varied mottling: more opaque in deep areas, where the pigment settles thicker, and more transparent on raised surfaces.

A 50:50 mix will treat approximately 30 sq ft per gallon — more if you spray, less if you use a brush and really saturate the mud. More saturation provides more strength and water-resistance. If you want to stretch your supplies a bit more, you can dilute it with a little more water.

Make sure to really fill every nook and cranny, otherwise, you end up with uncemented areas which will be fragile. When applying it, especially over deeply textured mud, it's almost as if you're pouring it on with the brush. As you'll see, it soaks in so fast you don't really have time to brush it. Strange stuff.

Spray bottles are a good way to apply it, especially if you want a thinner application. Coarse rather than fine spray is less of an inhalation hazard.

• Waterglass is mildly caustic, so gloves or regular hand-washing is indicated.
• While it’s liquid, it is still silica, and bad for the lungs; if you decide to spray it, wear a mask.
• Be careful of overspray and drips, as the stuff will mar glass surfaces, and can be hard to clean off of other surfaces as well.

1. Mud should be thoroughly dry before applying waterglass.
Waterglass, clay, sand, and water make a gel before drying out completely. Perhaps because of the very binding properties that make it useful, it can take some time for that final drying to occur. If additional moisture is still moving out from deep in the wall, applying waterglass too soon may further slow drying.
So a thick mud wall may just appear to be dry. If you apply waterglass too soon, and then get rain, you may end up with soft, jelly-like patches that can even slough off completely. If you’re not sure, better to let an earthen wall dry completely – a year, if need be – before waterglassing.

2. Let the waterglassed surface dry slowly.
Say you waterglass a dry wall on a sunny day. The next day you find it covered with white powder. Some of it brushes off easily, but some sticks and gives your final color an annoying dusty finish.
I’ve heard two explanations: one is that fast drying pulls both water and waterglass out at such a rate that the mineral ends up drying on the surface where it turns into powder; the other explanation is that the waterglass displaces other salts that may be present, and those get deposited on the surface. Either way, the problem seems to be exacerbated by overly quick drying. I waterglass late in the day after the sun is low and the heat has dropped.

earth, ovens, BREAD, art! - 2008 workshop schedule

2008 schedule: Earth Ovens Bread ART!

Hands-on workshops on wood-fired earthen ovens, good bread, natural plasters & practical sculpture; offered by Kiko Denzer, and others, as noted.

If you can make mud pies, you can build with earth. Good material is often underfoot. Practical, beautiful, dirt cheap, and faster than you think, mud is also sculptural, colorful, and rich, whether you make ovens, benches, garden walls, or houses. And you can do it with your kids! “Mud ovens” were the original masonry ovens (brick is, after all, fired clay). These ovens bake beautiful bread (and anything else), and perform as well as the fancy $4,000 Italian ones. You can build a simple one in a day, and learn enough about cob and natural building to start planning your cob cottage!

April 12-13, Ovens & Bread
Philomath, Oregon, Gathering Together Farms
Gathering Together Farm is a local, community-sponsored farm. Even though the workshop is over, the oven is still in progress (as of May 5, 2008). Come on by. Good food!

MAY May 31-June 1, Ovens & Bread
NE Portland, Oregon
A residential oven in a neighborhood setting. Probably bi-lingual, English/Spanish! Limited openings. $175, includes lunch. (also a good time to make mud at Portland’s annual Village Building Convergence, w/speakers, events, & building projects all around. See for more.)

NEW DATES: June 30-Jul 4: Earth & art for your home: design, sculpture, & decoration with natural materials
Coquille, OR, No. Am. Sch. of Natural Building, with Linda Smiley et al
Natural plasters, paints, and finishes to design, sculpt, and help finish an existing cob cottage. We’ll start with a review of the principles of design, site analysis, 3-dimensional space and spatial dynamics, and practical beauty. Then we’ll get muddy; work will be interspersed with discussion and demos covering technical, design, and materials issues, including earthen and lime plasters, clay paints, and sculptural mixes. Explore, experiment, gain practical experience to apply to your own design problems. The site features a broad array of earthen and natural buildings and related techniques. Contact the school at 541-396-1825, or see

July 26-27, Ovens & Bread
Pringle Creek Community, Salem, OR

August 23-24, Ovens & Bread, near Burnt Woods, OR, at the site of the future Oregon Folk School

We have taught at Bob’s Red Mill, Andrew Whitley’s Village Bakery (UK), the King Arthur Flour Company, and at the Bread Baker’s Guild of America’s “Camp Bread” in San Francisco. Kiko is an artist/ builder and author of Build Your Own Earth Oven (bread chapter by Hannah), & Dig Your Hands in the Dirt: A Manual for Making Art out of Earth (Hand Print Press). Hannah baked professionally for organic bakeries in the UK, and is also an organic gardener and massage therapist. Every other week, we bake 25 pounds of whole-grain sourdough in a mud oven. It’s a staple food. Groups are generally interesting, diverse, and fun; all learn, and all teach. We believe that cooking (and growing) food is essential to true culture. So by working, cooking, learning, and eating together, we build the living fabric of peace.

FORMAT: Both days combine oven-making with bread-baking, adjusted to suit participants. By the second day, we’ll have a “temporary oven” to bake in, and a more permanent oven to finish. We start working at 9 am, and are done by 5 pm.

ACCOMMODATIONS are not provided, tho some hosts may have space and camping facilities.

FEES: $175 per person for two days of hands-on learning, lunches, and snacks. For those with limited, low, or fixed incomes, we can and do reduce fees; please inquire.

TO REGISTER for the “earth and art in your home” course in Coquille, call 541-396-1825.

TO REGISTER for all other courses: Send a check or postal money order for 50% of the course fee, payable to Kiko Denzer, at POB 576, Blodgett OR 97326. The fee is non-refundable unless we can fill your space immediately. 20% discount for full pre-payment 3 weeks in advance. When we get your payment, we’ll send confirmation and other info.

QUESTIONS: 541-438-4300, or

APPRENTICESHIP OPPORTUNITY: This is a home-and-community based invitation to share in and learn from the life of a family that is trying to live, learn, grow, and eat as close as possible to their (rural) home, inspired by a vision of “every man (& woman) ‘neath their vine and fig tree, living in peace and unafraid” – and in community with (urban and) rural neighbors. Help w/garden, greywater, compost (toilet), plastering, cob building & repair, community events, ovens, art & sculpture projects, bread & food, noisy boys (2 & 5 yrs), creek, walks, a small publishing business, etc. 4 days work/wk, plus cash for room & board. Write and tell us about yourself! POB 576, Blodgett, OR 97326.

beauty and utility

There is an important, practical relationship between beauty and utility: to be beautiful, life must be useful, and vice-versa. The combination of beauty and utility is our common, human art. It seems to me that natural building, and particularly earthen building, restores that relationship.

Being human requires an understanding for and appreciation of fundamental harmonies. All the parts must fit together well. Thus art is essentially about harmonious integration, and beauty is essentially how we qualify harmony; our knowledge of beauty is what allows us to determine the goodness or “rightness” of fit. (Art, harmony, and a remarkable string of other words (including “reason” and “hatred”), all share a common indo-european root, “ar,” meaning “to fit together.” The root of “beauty” is a latin word meaning “good.”)

But our knowledge of beauty is limited when we lose touch, literally, with the world around us. If we don’t know the first thing about where we live, if we don’t know the soil, the plants, the animals, the stars, then how can we know harmony, or beauty? How can we make the right decisions? It’s difficult for many to even take the time to look — and I think knowledge of beauty requires time. One only knows beauty by direct contact; the more contact, the greater the knowledge — and vice-versa.

In Western society, however, artists are often deemed “unusual” or “different” in part because they may spend days or years in contemplation that produces nothing except, perhaps, a painting, sculpture, poem, or dance. “What good is that,” they say, “if it won’t even put food on the table?” So the “practical man” imagines that art, and it’s pre-requisite, contemplation, are solitary and useless activities.

Yet contemplation is, in fact, a fundamentally social activity in which we work with memory, imagination, emotion and reason to work out the harmonies of life. It is considered a solitary pursuit, because no more than one human is needed — but contemplation is born out of our relatedness to each other and the life we share. It is the critical tool with which we forge our relationships with every one of innumerable members of creation! And it is typically the result of some kind of encounter with reality, whether the encounter is a non-verbal experience of the world, a conversation, a book, or chatting to someone while your hands are busy making art out of muddy earth. So those “useless” actions of dreaming humans, in solitary or social contemplation, are central to our shared life. Contemplation is the conscious practice of the butterfly effect.

The social status of “artists” aside, as living bodies that fit together well and work, individually and in groups, each of us has tremendous innate knowledge of our own beauty, our own relatedness to the beauties of the world. Even if we aren’t in direct contact with them through our hands and eyes, we’re all constantly in our own beautiful, useful bodies — and whether or not we’re mentally conscious of that, we are physically in contact with it.

What a surprise, then, to find that such a simple thing as shaping the mud under our feet can restore that contact and that confidence, that we are indeed beautiful, and that we can integrate beauty into our lives and our relationships. Here you’ll see photos of people “jumping in the mud,” a “solitary” experience that is easily and directly shared, that produces smiles and laughter, and that easily progresses to become shared, practical labor that produces a building or a sculpture (or both in one) that is larger than our combined selves.

It is by such experience that we come to know the manifestation of our shared goodness, our common beauty. And it is by such knowledge that we acquire real authority — and it is authority that inspires hope — for every individual, as well as for the community — especially in a context where our institutions are failing, our individual confidence is under siege, and the world seems to be falling in on us.