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Steve D. 11-01-2009 10:46 PM

36'' or 42" oven?
Hi everyone. First time poster, but have trawled through many of the threads and have gained invaluable tips and advice.
My question is regarding oven size, and specifically the difference in time required to fire up the different sizes. I'm tossing up between the 36" and 42" dome ovens. I have room for the larger one and it is my preference, however my only reservation is if there is a much longer time required to fire up the larger oven to the appropriate temp. I would appreciate any comments on this aspect of wood fired ovens.

Frances 11-03-2009 02:03 AM

Re: 36'' or 42" oven?
There are a couple of threads addressing this question, so maybe read around a bit more to find them.

One I point I've made before is that you don't have to choose between the biggest and smallest sizes, but could make your oven any diameter inbetween - mine's 40 inches and suits me just fine.

As you say, big ovens take longer to heat up but have more room (and you probably will start making bread and roasts, whatever you may think you'll be needing the oven for now ;)), smaller ones work perfectly well and can also bake bread etc... so basically its up to you, there isn't a better or worse, they're just different (or at least that's what I think).

Heat up times can vary so much, depending on the wood you use, the weather, how long since you last used the oven, what kind of insulation you have, what day of the week it is.... Mine is usuall ready in a bit over or under an hour, depending. Hope that helps! :)

Alter ego 11-03-2009 02:16 AM

Re: 36'' or 42" oven?
I'm building a metric oven which is 1.0m diameter.

There are enough Aussies and Europeans on the forum now that we could start a conversion to metric. Want to join me on this mutiny???


texassourdough 11-03-2009 04:04 AM

Re: 36'' or 42" oven?
The heat loading of an ovens of different size and similar construction (i.e. both refractory) or both brick of similar thickness is primarily a function of temperature difference within and across the wall. The temperatures and radiant heat load inside the oven should be similar if you build a similar but slightly larger fire so the times should be similar. The time to heat up will be similar. Higher mass ovens with thicker walls will take longer. I will almost guess that fire starting and burning style have more to do with heating times than oven size.

My one meter oven is typically cleared in about 45 minutes and ready to go about ten minutes later. I don't have a lot of experience with other ovens but I would be surprised if the heat up time was much more than five minutes difference between similarly fired 36 and 42 inch ovens.

What makes a big difference is mass - particularly in the form of thicker walls. Barrel vault ovens can take several hours to heat load but they can do three batches of bread.

I agree with Frances. Unless you have a reason to build a big oven,the one meter ovens are a good compromise. After having a one meter I would find 36 cramped but I also have no use for the extra space and a bigger oven needs more bread to get appropriate humidity for great crust so I would personally not go bigger. will almost certainly be happy with whatever you build!

Good Luck!

ThisOldGarageNJ 11-03-2009 04:14 AM

Re: 36'' or 42" oven?
Hi Steve,, (welcome to the forum)
I built a 42 inch (1.0668 m) Pompei Oven.. I think heat up time is going to be a minor debate on this one, difference should be minimal.. I usually heat up for pizza in less than an hour.. and dont forget, cooking pizza s usually done with a live fire in the oven to help keep a good heat going... But If i want to bake, cook a chicken, etc, I will heat the oven for a minimum of 3 i want to load my thermal mass with heat so i can take the live fire out of the oven...

Hope this helps


dmun 11-03-2009 05:29 AM

Re: 36'' or 42" oven?
I specifically made a small, thin wall brick oven with the idea of quick heat-up, and mine seems to take about the same time to heat up as everyone else's. I would say size is a secondary consideration. Dry, small firewood is the main speed consideration, in my estimation.

You can't avoid physics: It takes more wood to fire more mass, and things happen faster in hot dry weather than they do in cold damp weather. There are many variables.

Short answer: build the size oven you think you need.

kebwi 11-03-2009 08:04 AM

Re: 36'' or 42" oven?
My theory on heat up time would be that it is purely a function of wall thickness, not oven diameter, with the caveat that a larger oven requires more wood overall. Thus, all half-brick ovens (Pompeii) should heat up in the same time. I don't have an oven of course, and even if I did, I wouldn't have multiple ovens to compare, but that's what makes sense to me. Is that not what other people think?

texassourdough 11-03-2009 08:25 AM

Re: 36'' or 42" oven?
Lots of good comments dmun & Mark. My only divergence would be that my refractory oven is adequately loaded for one batch of bread or a chicken after only an hour and a half or so. Three hours is good but probably more than is necessary.

On a simplistic level you are right kebwi ASSUMING ALL OTHER FACTORS ARE CONSISTENT. Which they aren't. Wall thickness is an increasingly important factor as the walls get thinner. Wall material also has some impact. My oven is refractory cement and that will have somewhat different heat transfer properties and heat capacity than fire brick. Fire variables are also of critical importance (dryness of wood, specific wood used, size of fire, nature of tending, all have an impact).

I have heard really short heatup times for the Primaveras (like half an hour) and will guess that is because they are thin. But thickness is ultimately not all that big a deal because the inside surface temp is a fxn of both the heat being absorbed from the oven and the heat being lost (transferred) to the outer, cooler parts of the oven. You don't have to have the transferred heat all the way through the shell for the interior surface to reach 750 and clear and thus be ready for pizza. So the pizza time for a 6 inch thick oven and an 8 inch thick oven may be virtually identical. At two or four inches it would probably make a difference.

Your ultimate conclusion...however is I think very correct in that half brick Pompeii ovens should be expected to have very similar heatup characteristics and times for any given person (for they will would tend to use the same wood, and fire technique in any size oven).

kebwi 11-03-2009 08:57 AM

Re: 36'' or 42" oven?
Oh yeah, obviously. I meant for a given material, say, firebrick. I was just responding to the original question. I'm certain that ovens made of different materials would saturate with heat at various rates.


jmhepworth 11-03-2009 09:58 AM

Re: 36'' or 42" oven?
I decided to go with 42. I was pretty sure that I could do everything a 36 could do with a 42 but I might not be able to fit some things into a 36 that I could in a 42. And I had the space for the 42. I have fit 3 pizzas in a 42 and there's not a chance I would try to do more than that. Way too much going on at once. But most of the time I cook one or two at a time, something a 36 would be perfectly adequate for.

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