Pompeii oven - too thick?

[Smiriglio]

Re: Pompeii oven - too thick?

Thanks, I thought it was nuts too.

[dmun]

Re: Pompeii oven - too thick?

I don't know what you would gain from building a dome from splits and covering it with concrete. Castible refractory is more expensive per unit of mass than firebricks in the US, particularly if you use the recommended stainless needles to prevent cracking. If the goal is just reducing mass, you also reduce strength, and the ability to hold heat.

[Smiriglio]

Re: Pompeii oven - too thick?

Has anybody used the thinner fire bricks to make the dome. Although they do not cost any less, their use may provide less mass and more room for insulation. Instead of laying the bricks in the "classic" manor, I am thinking of making a wooden form that I can lay the fire bricks on [like tile] and then cast the entire dome in a few inches of thermal cement. I would also build an outer dome to allow for the addition of the vermiculite fill. Is this nuts?

[Barberque boy]

Re: Pompeii oven - too thick?

I'm curious do you support the idea of wrapping the oven with wire and mortar for strength and/or mass or just support the idea of 4 1/2" thick fire brick.

"Since Jim brought up this historical thread, I should add that I no longer think the half-brick thick dome is too thick. The additional thickness adds only a little to heat up time, and adds a great deal to dome strength and stability."

[edschmidt]

Re: Pompeii oven - too thick?

I cast my pieces at 4 in. and added an additional 2" of remesh reinforced concrete on top. And the other thing I measure with displacement.

[gjbingham]

Re: Pompeii oven - too thick?

edschmidt,
I concur completely. Please explain your six inches of mass. That sound dirty, but for the time being, I'm not joking.

[edschmidt]

Re: Pompeii oven - too thick?

My 36" oven has approx 6" of mass and I LOVE having the ability to throw a pizza party on sat. night, Wake up at 10:30 on sun. (sorry pastor) and throw in a roast which will be done around 6pm sun afternoon. I dont bake a ton of bread, but realistically a full burn of seasoned hardwood is going to take a good 2 hrs. before the coals are gone. Why not store all of that heat?

[dmun]

Re: Pompeii oven - too thick?

Since Jim brought up this historical thread, I should add that I no longer think the half-brick thick dome is too thick. The additional thickness adds only a little to heat up time, and adds a great deal to dome strength and stability.

[SpringJim]

Re: Pompeii oven - too thick?

I love researching the historical posts on FB...

It's amazing how many times we can go around on very similar but important issues....
....the truth is out there.

Thanks to all those old time FB members from '05 who still contribute and stay in touch! Thanks.... David, Rick, Bob, Les, Wade, Luis, Marcel, Kiwi, Michael, Jim, Keith, Southpaw, and of course James (and all the others surely missed !)

This collective knowledge, experience and opinions is a valuable energy and inspiration within the growing FB community.

[Marcel]

Newbie returned to round - igloo after much research

#16

(M) "fmed" wrote:

(F) "
This is my rationale behind designing a rectangular oven with a precast vault. It looks easier to build. I'd love to have the time and space to build a Pompeii style dome, but I am frankly intimidated by the brickwork."

================================================== ====

(M) I was in your position but compelling arguments by Jim, James, Paul and Robert Musa finds me back to "circle one" ;-)

(M) It is not too late for me to change my mind, Fred, but I would need to read even more compelling arguments than those offered by my "oven gurus". I have read virtually every post in this Forum I could find.

(M) The following are some of the reasons I returned to the Pompeii design:

1- There has been such detailed and thorough analysis here that I have a lot of confidence in getting guidance. If you look at the "vault" sites, I don't believe you'll find this kind of cyber support.

2- Robert Musa convinced me that the dome is stronger; even when built to less than rigorous tolerances.

3- Fred di Napoli turned me on to a template that comes with a CD and is available at Home Depot (mine sells them for $16.95) that does all the Math. for not just the number of bricks per ring, but the angle of the wedge shapes required. The movable template will let you project those angles onto your bricks. A cheap ($85) tile saw that cuts 1-3/8" will let me either cut about 1/2 way and split, or, for visible surfaces, turn the brick and let me cut all the way through. The "Angleizer" is the name of the template and CD Combo.

4- "Paulages" (don't we all, Paul?) has contributed a great many terrific photos of his process. He indicates where he would have done things differently and makes excellent recommendations.

(M) These are not the only really active members here. There are David, Luis, Hope, etc. .... all of whom are available to help you. Yes, the comraderie of a community oven building outdoor workshop is enticing but we have a cyber community that is open to exploration. They do not build only by formula. There is terrific variety here.

(M) Note that I have said nothing of mass because like many, I believe either foot print can be utilized with greater or lesser thermal mass.

(M) Ultimately the decision as to footprint is yours and I'm sure your views would still be welcome here if you chose not to go with the Pompeii.

(M) Good Luck irrespective of your decision!

Ciao,

Marcel

[Robert Musa]

but I am frankly intimidated by the brickwork.

ha!! once you build the base and the hearth form you become imbued with magical brick laying powers. i actually found building the dome to be the "zen" stage of the oven construction as opposed to the "man with a hoe" aspects of the other parts...

[fmed]

question: would it be more difficult to build a structurally sound thin oven for those of us with stubby fingers?

This is my rationale behind designing a rectangular oven with a precast vault. It looks easier to build. I'd love to have the time and space to build a Pompeii style dome, but I am frankly intimidated by the brickwork.

[Robert Musa]

thinner might be better. here's my (amateur ) reasoning.

assuming all other aspects of the oven are identical (except brick thickness);

1. it would take less fuel to heat the smaller mass to a given heat (or the mass could be heated in a shorter period of time given the same amount of fuel). thin wins...

2. the surface area of the domes (both interior and exterior) would be roughly the same (exterior surface of thick oven would be somewhat greater). so one would expect the number of btu's lost through radiation over any given period of time (the bleed rate) to be about the same. thus, once the oven reached pizza temp, both ovens would require about the same amount of fuel to replenish the lost btu's. maybe a tie - maybe advantage thin ....

3. because the thinner oven stores less btu's, once the fire is removed (or becomes smaller than the amount required to replace lost btu's) the thicker oven would require a longer period of time to return to ambinent temp than the thin oven. thick wins ...

question: would it be more difficult to build a structurally sound thin oven for those of us with stubby fingers?

like paulages, i find that maintaining a "super hot" oven requires attention. in our last pizza go around i adopted the previously discussed method of lots of wood right up front and was able to get the dome over 1000 (f) within 90 minutes, however the bleed rate is a pretty steep curve at that temp.

i have a theory that the height of the dome may have more to do with getting 90 second pizza than anything else. (mine is too high). then again, we're just guilding the lily here. my experience is that anything which comes out of our oven is better than anything we can buy in a restaurant by a factor of 10. i would be surprised if tweaking this a little one way or another will result in dramatic differences.

[fmed]

Thanks for the quick reply James. I have read that very informative Why Round page. Thanks for writing that.

If the vault is a pre-cast piece, would there still be the outward thrust issue? If so, I would imagine some steelwork could alleviate this without adding thermal mass.

Decisions, decisions....

[james]

Ciao Fernando,

Take a look at the "why round" page -- it has some good information on why round ovens are a good idea for pizza.

http://fornobravo.com/pompeii_oven/why_round.html

In general, regardless of mass, round ovens do a better job of storing and reflecting heat for pizza than rectangular ovens. I think you can make the case that the rectangular foot print is more efficient for a commercial bakery producing lots of bread. I think this is why virtually every pizza oven in Italy is round.

Also, the outward thrust of the dome of the barrel vault forces you to use a certain amount of concrete (or an engineer butress system ala Notre Dame), which drives up the mass beyond where you want it.

I have a thinner mass barrel vault oven (split firebricks set on the thin side), that still has a lot of concrete around the dome. It really doesn't cook pizza nearly as well as our Forno Bravo precast ovens, or a Pompeii oven -- in terms of heat, heat up and even, consistent heat on the floor. Also, the rectangular footprint is a pain when you are trying to do lots of pizza.

My two cents.

Have fun and share your progress however you decide to go ahead.

James