Thursday, March 24, 2011

Blogging and Publishing

As of March, 2010, I'm consolidating all my blog posts here, at Hand Print Press, which now also has pages where anyone can submit posts on topics related to earth ovens, community earthen art projects, learning-by-doing, Making Things, and the like. Publishing originally meant the simple act of taking a story to the public so it could be shared, amended, learned from, improved. In those days, "the media" consisted of true crafts — sculpture, painting, song, dance, theater — it's only recently that "media" has been limited to print, paper, and now, bits and bytes. But people are still people, despite the growth of industries that would reduce us to mere "consumers." At Hand Print Press, we're trying to use privatized linguistic cyber-tools (aka the web) to support the arts of fabrication, discourse, and story, and to nourish living crafts and public health — it's all learning by doing.

Thursday, December 30, 2010

Masonry "hat" for an old box stove

My old cast iron box stove heated up my office quickly, but was hard to regulate, dried out the atmosphere, burned a lot of fuel, and cooled off quickly. Now, with a little masonry "hat" to capture the heat that was previously vented out the chimney, I heat up a few hundred pounds of bricks and mud which radiate a gentle heat into my office for up to 12 hours (depending on how much wood I use).
The surface temperatures are much lower than hot iron and (except briefly, at it's hottest), very huggable. In addition, I lined the firebox with brick, which makes the metal surfaces less dangerous, and increases combustion temperatures for a cleaner burn. Once hot (which takes up to about 10 minutes), there is no visible smoke coming out of the chimney. I typically burn it for less than an hour and have heat all day (I live in western Oregon, so it's not that cold). In my under-insulated cabin, the "hat" usually holds heat until the next morning. The stove was an old cast-off that now provides clean heat with minimal smoke. Oh, it also has a little "white oven" that we can bake in (note the wooden oven door on the lower R).
I don't have the technical apparatus to do the testing, but I do have neighbors with "approved" stoves that they load up with damp fuel that they allow to smolder all night long, clogging their chimneys with creosote and putting clouds of grey smoke into the blue sky.
Here's a quick video that gives you an idea of what's inside the heater. Most of the bits are recycled brick and tile, with a few new firebricks for good measure. The base I cast from special hi-temp cement.


Wednesday, December 8, 2010

efficacy of firing doors


Watch (and listen) how the firing door improves combustion. How it works: the chimney determines how much air can get into the fire. Without the firing door, the air all goes in at once, and the fire burns primarily at the edges, where air meets flame. The firing door, however, limits airflow, forcing the fire to suck in a smaller "jet" of air. Because it's smaller, the jet has to move faster in order to get the same amount of air into the chimney. Increased air speed and pressure create more turbulence and better mixing in the fire -- you can hear it quite clearly, even in a low-quality video. Better combustion makes more heat, more heat heats up your oven faster. (Note that the opening is at the bottom of the door. Letting the air in at the top would interfere with the hot gases trying to get out.) So, to optimize combustion in your wood-fired oven:
1. use bone dry fuel (boiling away any water in wood takes over 500 times as much energy as just heating up the wood itself),
2. burn only a small amount of small pieces (more surface area means better mixing of fuel and oxygen, and more complete combustion; there should always be enough space around the wood for combustible gases to expand and burn completely. I would say roughly 1/2 to 2/3 of the volume of the oven chamber should be free of fuel),
3. maximize turbulence (a firing door: the openings should have an area approximately equal to the cross-sectional area of the chimney -- for most home ovens, that will be somewhere in the range of 20-30 square inches -- or about 4x5 to 5x6 inches.

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.