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Old 03-22-2006, 11:31 PM
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Default Oven in the snow

Jim,

We get a lot of questions about how brick ovens perform in the cold and snow. I've seen photos of ovens in deep snow, and have cooked outside in light snow and reasonable freeze, but I wanted to ask how your works in serious cold.

Would you mind giving us the background on how your oven works, and what to expect?

James
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Old 03-23-2006, 07:48 AM
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Default Ovens in Snow

James,

Through trial and error and frozen hands , I've learned several things about oven performance in cold weather. All the following is oriented to bread baking. First off, it's really, really important to orient the oven door directly opposite the prevailing wind (here, from the northwest and quite strong and steady in January). Second, cold, dry draft air has a drastic effect on firing times, unlike, say, the more humid warm draft air going into an inside wood stove or summer temp air, because it's cooling both the fire and the brick; working against you, in fact. This also has an effect on the initial fire, and it's important to make sure that you get a bright burn going right away. A draft door is key, almost from the very beginning. Overall, you have to tend the fire more in cold weather. My oven is high mass (9 inches, refractory cement), so in winter I need two full burns and about 8 hours to bring it up to baking heat if it's dead cold at the start, but I'm after multiple bakes from one firing. The hearth will reach about 850-900 F, but the dome and cladding will be at about 550-600 before resting, but in winter the rest time is pretty short. I'm still experimenting with that timing. It's vital in winter to get the cladding about as hot as the dome. Otherwise, there's just too much wrong way heat transfer. Although I went a bit nuts with insulation (11 bags vermiculite and batts over that, around 7-8 inches total), the ability to hold the heat is drastically lessened in winter when overnight temps might drop to 20 below Celsius or lower, but, still, the hearth will be at about 350 F the next morning (the hearth bricks are set on a 6 inch refractory slab). I plan to add more insulation in the spring, and I'd like to know some details about the batt insulation the store has, or maybe blue foam board would be better over the vermiculite? So you'll understand the structure, the dome is surrounded by 4 inch block walls set on an 8 inch block foundation, an inch of air space, and brick all round for the facade. The ceiling is made from metal studs, with cement board laid over them. I vented the small space between the top of the insulation and the cement boards. The roof (vented) is made from wooden trusses (34 degree pitch) with cedar shingles.

As for fuel, it must be absolutely dry and seasoned. For full burns, I use wood cut to just shy of the depth of the hearth, so it burns front to back. I've found that, as Alan Scott says, you need a bright burn, so I've begun layering my fires. I start with softwood kindling (even 2x4s will do), then hardwood branches, then some split hardwood stovewood about 16 inches long. Next, for the first full burn, I add longer pieces of mixed softwood and hard to get it really roaring with the draft door in place. I find this spikes the temps fairly quickly, at least on the surfaces. Once that's gone to coals, I spread them out pretty evenly on the hearth floor, and pile on mainly hardwood, mixed with cedar to get a quick catch. This is a slower burn, with more BTUs, but in winter you have to be careful that it burns, not smolders or glows, which would be okay in a wood stove but not here. In the second burn, I'm looking for a sort of plasma effect inside the oven. That's when the heat is really coming on. But, in winter, you just plain need more wood, a lot more. I've found, too, that you have to tend this second fire to make sure it's burning brightly the whole time, and add to it if necessary, or else you stall at a certain temp, usually about 600 on the hearth.

Although my vermiculite layer below the slab is thicker than the AS plans, I still feel I'm losing too much heat from the bottom in winter, so I'll be adding about two inches of, I think it's called GlasClad insulation used as house sheathing, below the vermic layer. Unless, of course, someone knows of something more effective. Even though my oven door faces south, I'm planning to glass in the walls of the seven foot long portico in front of the oven (see attached pics), which I might even heat in winter. I'm hoping this will control the draft better and raise the draft air temp. I guess overall, what you're fighting in winter is the temperature of the draft air, wind (here, very strong at times), and the temperature of the bricks at start-up. Just so you know, the chimney draws very, very well. The AS plans call for 8 inch square flue tiles, but I used 7 inch round, because I've found round draws better.

One solution that's turned out to be effective in cold weather is to light a smallish fire the night before the bake. The Bread Builders suggests a "small" fire, but I've found that sub-zero requires something bigger than that, about what you'd put in your inside wood stove overnight. I've found that split hardwood is best for this, and it's okay if it burns slowly, better in fact. This preheating really helps in the initial burn the next day and causes the cladding to absorb a fair bit, somewhere in the 250 F range. Preheating also means the first burn, well, burns better because the bricks are at least warm. I'd prefer to stick to using wood, but I'm wondering whether, in winter, I might be better off with something like an industrial salamander propane heater overnight . Of course, I've been baking on a fairly small scale this winter, about 50 loaves a week, and I suspect that when I start baking on an almost daily basis, winter heating times will lessen because the cladding will remain at a higher heat from day to day.

Having said all that, it might be worth knowing that the climate here in southern Ontario is relatively mild by Canadian standards. To the south, across Lake Ontario, northern New York gets quite a bit colder, so, too, New England, which is a fair bit north of here. Maine in particular. We're on about the same latitude as northern California

I'm really in my infancy for cold weather oven management, but these are the things I've discovered during my first winter baking. I would really welcome any comments from more experienced cold weather bakers.

Jim
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  #3  
Old 09-18-2007, 10:29 PM
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Default Re: Oven in the snow

James, what would you consider serious cold? 30degrees, lower? Pebble in winter is 50's- correct? Maybe 40's a couple days. Reno/ Carson can get to 10 below like last winter.
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Old 09-19-2007, 04:53 AM
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Jim,
an excellent report!!Congratulations on a job well done (from an adult educator).
It makes me all the more appreciative of what must then seem very mild mediterranean climate here in South Australia, maybe very cold on a 4įC day, very rarely below 0į (only a couple of times in 50 years).
Sorry that I can't add to the posting but had to comment on Jim's report.

Neill
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Old 09-19-2007, 06:37 AM
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Default Re: Oven in the snow

It got to 20F here a couple times last winter and I like to froze! I'm never going to Canada!

Is the storage area under the oven open or closed? If open, try putting a door or even just a plastic curtain over it. That way the cold air isn't sucking heat away from the bottom of the slab as much (we do something similar here by enclosing the space under houses with pier foundations and it helps).
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Old 09-19-2007, 08:45 AM
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Default Re: Oven in the snow

Neill, are there children as educators on this forum?
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Old 09-19-2007, 05:41 PM
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Default Re: Oven in the snow

Living near the ocean is pretty unusual. It's cold and foggy in July and August, then warms up in Sept and Oct. The hotter inland areas draw in the fog from the ocean that keeps the coast cool in summer. If you drive inland about 40 minutes, you go from 60ºF to 95ºF. It might even be hotter here in the winter than the summer. I don't think it ever gets lower than 50ºF (about 10ºC). Pretty unusual.

I really miss the Florence weather. That is a real four season climate, complete with blistering heat in the summer and frost (and the occasional snow) in the winter. Just when you get tired of one type of weather, it's starting to change.

Oh well. My oven is coming soon, so I will be outside enjoying the cool fog. That's something to look forward to.
James
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Old 09-19-2007, 07:12 PM
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Default Re: Oven in the snow

James - Pebble Beach, cry me a river They are calling for snow tonight on the hill. Had to cover the project up tonight with tarps.

Les...
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Old 09-19-2007, 08:02 PM
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Default Re: Oven in the snow

James, your detail reminds me of that same temp range and heat/ cold factor. I lived in San Mateo a number of years, as well as Tracy.
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Old 09-19-2007, 10:43 PM
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Default Re: Oven in the snow

Ah, San Mateo. The Penisula has great weather. The US Geographic Society (I think) is in Menlo Park, and one of the weather groups claims that Palo Alto has the best weather in the U.S.

Rarely freezes, not too hot in the summer, and warm evenings. Great lemon trees and mature bouganvilla.

Les, this is pretty early for snow! How high are you?

James
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