Thursday, August 14, 2008

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


Jim Buckley said...

I found Noah Elbers' experience with cob and AS ovens very interesting and instructive.

I built a 36" Superior Clay oven in our office. See

It's taken me a little practice but I have found that it's really important to get the oven "saturated" - hot enough - as Noah says. This oven, which is only 36" in diameter inside with walls about 4" thick plus another 4" of fiberglass and insulating concrete, takes about three hours to get "saturated" to about 1,200 degrees - or whatever temperature burns the inside clean and my 1000 degree thermometer is pegged. Since it is lighter (and smaller) than Noah's cob oven it heats up faster but also cools down faster so that after four or five hours it's only about 400 degrees.

More comments and construction details at

Jim Buckley

edinburghwhisky said...

just to say this is a great site ,i have just built my own oven and was having a problem getting a handle on heat and what to cook when
good advice on the blogi appreciate it
take a look at ours

keep cookin !!

Hilton said...

Hi : My son is building a clay cob oven in Mexico, and I wondered whether it would be helpful for him to know the inside temperature, using some kind of thermometer that he could remotely read from the outside and so he could more precisely time the baking cycle. If so, where would I find such a gauge ?

Hilton said...

Hi : My son is building a clay cob oven in Mexico and I wondered whether knowing the inside temperature would help him with the baking cycle.
I was thinking of a thermometer with a sensor in the oven, and being able to read it remotely outside the oven. Would this help ? If so, where would I find such a device ?

Kevin Kossowan said...

Thanks for sharing his perspective. I was actually planning, for nearly a year, to build an AS oven, but I've read too many compelling arguments not to. This was one of many nails in the coffin. [another being a recent re-read of your book]

Dorie Goldman said...

Hi Noah and Kiko,

I was up and visited Noah in the fall at his bakery. I'm in Amherst, Ma, where I am starting a sourdough bakery. I've been baking and selling out of my kitchen and told Noah I was planning to build a cob oven in the backyard, but plans change, and I am now buying a house with a detached garage which I plan to convert to a bakery. What I'd like to do is to build an oven onto the back of the garage, so that the oven door opens into it. Advice? I'm concerned about the smoke, both filling the bakery and the neighbors' yards. Also I am hoping to be able to fire it before I go to bed and bake first thing in the morning. Is this realistic?

I fear that this rocket idea would completely freak out all my town inspectors, from whom I'll need all sorts of permits. They are extremely strict about such things in this town. And the smoke could be problematic for the same reasons.

Any advice would be appreciated!

Dorie Goldman