#11  
Old 12-20-2007, 07:45 AM
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Default Re: I think oven mass needs to be brought back up.

Dave,
If I remember correctly, you bought used bricks (?). I'm wondering if you perhaps got medium or high duty fire bricks, such as those used for kilns etc. that take more heat to get them up to temperature, but hold the heat longer once there. That might explain the longer firing times but great heat retention.

George
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  #12  
Old 12-20-2007, 10:01 AM
Peasant
 
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Default Re: I think oven mass needs to be brought back up.

It's interesting that this comes up just as I've been wondering about adding mass to the oven floor. I was specifically thinking about laying the floor bricks on their edges increasing the floor thickness from 2.5 inches to 4.5.

I was thinking about this because I have notice several posts where people mentioned that the floor quickly lost heat. I was wondering if the pizza itself sucked heat out of the floor, and if each subsequent pizza should be made on a different part of the floor to allow the previous floor section to re-absorb heat reflected from the dome.

So would a thicker floor hold heat longer and would it be so thick that the fire time would be to long?

I notice that Dutchoven was also thinking along these lines,
Quote:
Less mass less time to heat up yes but, brickwork has to be spot on because the line of thrust has to fall within the inner 1/3 of the thickness of the brick...on a 2.5 inch thickness that leaves only a little space. I suggested on an earlier thread(one that I can't find right now) that the lower courses(1-3) be comprised of 6 inch units created, then through the middle courses go to the bricks cut in half 4.5 inch units and then the last 3 or four courses go to 3 inch units. This design would load the haunches of the dome and thin out the upper level of the oven to(in theory) shorten heat up time. As for thickness of the floor, to me it would be a personal choice...my oven floor thickness is about 4.5 inches
Dutch is your oven finished? Are you happy with your floor thickness?
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  #13  
Old 12-20-2007, 10:30 AM
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Default Re: I think oven mass needs to be brought back up.

Quote:
Originally Posted by Dannyboyblue View Post
It's interesting that this comes up just as I've been wondering about adding mass to the oven floor. I was specifically thinking about laying the floor bricks on their edges increasing the floor thickness from 2.5 inches to 4.5.
There is a lot going on in this thread. :-)

First, for those of us who have been doing this for a longer time, the question of whether a 4"-4.5" thick round oven dome has too much mass, not too little mass, is validation that we are doing something right. When I started FB, the only resource available in English was the Bread Builders, which describes a 9" thick dome and 9" thick floor. I built it, saw the problems, and started writing about it -- and caught a lot of flack. Some of it pretty nasty. It was as though I was criticizing a cultural icon.

So let's enjoy the moment to appreciate breaking through that problem.

In terms of the question, I believe that a 2"-3" dome and floor are perfect for home cooking. They heat up quickly, hold high heat (that is critical -- more to come on that), and they hold more than enough heat to bake and roast anything you want to cook. The FB residential ovens are all in this range, and they are the real deal; made in large volume in Italy and used by huge numbers of home owners.

One other note. Commercial pizza ovens, hot 365 days a year, are about 4" thick.

The issue with the floor, and to a less degree the dome, is keeping it hot by recharging it with your fire. A thicker floor actually makes it more difficult to maintain high heat -- because the thicker mass will wick heat away from the oven chamber to the outer mass of the floor. Definitely stick with the brick on its thin side for the floor.

Here is a copy of the Holding High Heat graphic.

Hope this all helps. Great topic! :-)
James
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I think oven mass needs to be brought back up.-holding_heat.jpg  
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Last edited by james; 12-20-2007 at 06:39 PM.
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  #14  
Old 12-20-2007, 10:48 AM
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Default Re: I think oven mass needs to be brought back up.

Auroville Earth Institute is a research, design and developing agency for vaulted structures, construction of various Vaults, Arches, Domes (VAD).

Quote:
Originally Posted by dmun View Post
At the end, there is an interesting condemnation of cement-based mortars. Of course these folks are working with compressed earth blocks, or adobe.
...hmm, I didn't notice that bit. What exactly are they saying, why are cement-based mortars supposed to be a bad idea?
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  #15  
Old 12-20-2007, 06:20 PM
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Default Re: I think oven mass needs to be brought back up.

I agree 98% with James, the other 2% I still agree but with a little reservation. The oven I constructed is of a Scott style. The brick are laid on edge and therefore 4.5 inches plus concrete of 3 inches for a total of 7.5 inches and the walls and dome are 4.5 inches of brick plus 3 inches of concrete for a grand total of 7.5 inches. It is a lot to heat up. I like James deal with the drawbacks. 2 to 3 inches with lots of insulation is PERFECT in my very humble opinion. Now for the reservation, comes the same as in my last post. For amateur builders like most are constructing a structurally sound dome with only a 2-3 inch thickness is a difficult process. The modular ovens are made to fit together and be structurally sound. So in truth I am 100% behind James on this.
Dutch
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  #16  
Old 12-21-2007, 09:02 AM
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Default Re: I think oven mass needs to be brought back up.

For the record, I added about 1" of extra refractory mortar/mass to my regular 1/2 brick dome, it still heats up quickly (45 min to 1 hour) and I have plenty of heat for several bread bakes. So for those who don't want to try to engineer a sideways/thin brick oven, don't worry, the regular design is most excellent...
Drake
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