Pompeii oven - too thick?

[fmed]

Hi All,

(...new here)

I thought I'd bump this thread since I'm in the research phase on building my own pizza oven. My goals are to build an oven specifically for pizza (and if I can bake a few loaves of bread afterwards -- bonus!)

The Pompeii page on this site asserts that this oven heats up quicker than a barrel vault oven. Is this really true? I can see that this is true for an Alan Scott oven with the thick thermal mass. Can you not build a well-insulated barrel vaulted oven with less mass (or no mass) which will heat up just as fast?

I'm currently leaning towards a rectangular oven with walls and floor of regular firebrick. The vault will be cast refractory done in sections. For insulation I'm thinking of using dense mineral wool (maybe 5" thick?). The outside may be clad with cement board on steel studs. Then stucco for the final surface.

Here is a reference:

http://mha-net.org/msb/html/bakeov17.htm

Looking for feedback,
-fernando

[paulages]

more fodder for an 'advanced building" section?

i thought about this same concept when building my pompeii, but didn't quite have a total grasp on what that would actually mean-- in terms of the building process and what that would change. so i followed the instructions gratefully and now have a well-functioning oven.

i can see the benefits of an oven with less thermal mass, and especially a floor with less thermal mass. i would like to see how this would affect overall temperatures. i ended up cutting all of my bricks with a 10" bricksaw anyway, so cutting them into thirds would have been almost as easy.

to keep my oven as hot as i like it for pizza, i have lots of coals and at least a couple of large logs really putting out a large flame. as soon as my flame is not licking all of the way to the top of the dome and a bit over, the floor begins to cool down below 600 deg F, and upper dome below 850 F. 90 second pizzas become impossible, and the crust starts to suffer and toughen up.

i can't help but wonder if less thermal mass and more insulation would help?

[james]

Dmun,

I think this has a great deal of merit. It's also interesting (ironic?) that you would want to develop this theme, when early on in the development of the Pompeii oven there were many people who had read the Breadbuilders book and thought the oven had too little mass. Of course that isn't right, and your posting touches on some interesting ideas. Don't forget that the barrel vault oven has something like 9 1/2" thick walls (4 1/2" brick and 5" concrete) -- so you can see the irony.

As an aside, I have fired my barrel vault oven a couple of times now, and am finding it as challenging as I feared. More on that later.

To your points:

1. Yes, you can definitely lay the cooking floor directly on the insulating layer. Many of the precast oven installation guides say that you should do that.

2. I will be looking forward to seeing responses from previous builders on whether they think the effort of the extra cutting is worth the return of having a lighter dome. From a practical perspective, the real issues are heat up time and heat retention time. You want the oven to heat up as quickly as possible, while still holding enough heat to cook lots of pizza (and the oven not give up), one batch of bread and a turkey (with veggies), which might be the most challenging. The FB precast ovens are designed specifically to do just that, and it would make sense that a site built oven could be tuned to the builder's specific requirements.

Thanks for the thought provoking posting.

James

[dmun]

Ok, I'm gonna say something that may be completely wrong, but I'd like some feedback from people who have practical experience. In my field (clockmaking) there's nothing more irritating than some amateur, who has no experience or feel for the traditions of the craft, get on some list and say that something that has been done for hundreds of years is completely wrong. So here goes.

I think that for the purposes of a home oven that the pompeii oven is too thick, or has too much thermal mass. For my purposes, I want an oven that will heat up quickly and efficiently to make some pizza, and retain enough heat to bake one batch of bread, or at a stretch, bake the Thanksgiving turkey.

For my purposes, I don't think the oven needs to be much thicker than the commercialy made refractory pizza ovens. It seems to me that that with three simple changes, I'd get an oven that's much more fuel efficient, and is ready to bake more quickly:

1) Lay the oven floor with the fire clay slurry directly on the insulating layer of the hearth, without that addtitonal slug of concrete for thermal mass.

2) Make the first, or soldier course, of the oven with wide side of the half bricks facing in, instead of the narrow side.

3) Build the dome with fire bricks cut in thirds rather than half, reducing the thickness of the dome from 4-and-change to two-and-a-half.

Now I know that cutting the fire bricks in thirds will leave some bricks without a factory edge, and a cut face looks different than a factory face, but I could use these middle sections on either side of the opening where they are less visible. It also means that each brick needs full cuts rather than score-and-break treatment, but I'm inclined to get the big brick saw anyway.

I don't mean this to be critical of the people who have designed and built the pompeii oven. I know the project was designed to built by beginners in masonry, who could split the bricks with an inexpensive brick set. I just think that these few changes could make it a better home oven.

Any comments?