42" Pompeii Beginnings in VA

[ConstantBuilder]

Hello everyone,

I have been lurking and learning on an off for a few years. I am at the point where I now have time to jump in and start building the Pompeii.

I am going to build the 42" oven with the normal dome (vs. low dome.) I intend to do a lot of bread baking in addition to weekend pizzas. I am looking to maximize heat retention, so I am looking at beefing up the insulation. I found what I think is a good deal on CalSil and FoamGlas at around $5/sq foot picked up. My plan is to go with 2" FoamGlas and 4" of CalSil on top of that. I am also going to incorporate a steam injection setup at some point for the bread. Someone on the forum did this with a pressure cooker and valves that fed into the oven with copper tubing.

So, the questions start. This starts to add up in height on top of the hearth slab. I am wondering if it would be good to inset the foamglas in the concrete and then add the CalSil on top of that? That does raise some concerns with water, but I could put in some weep holes on the concrete under the FoamGlas. The other option is to just build up from the slab and end up around 8" above slab with the oven floor. I guess that really doesn't matter, I just have to drop the height of blocks or slab to get to a comfortable landing height. Any thoughts on this would be appreciated. It seems like the 8" height above slab may look a little awkward, but maybe it will all be hidden behind the framing.

If I go down this path, it seems that it would be safe to skip the vermiculite in the hearth slab. Again, thoughts would be greatly appreciated.

These are my main questions right now. I think the hearth buildup will control any moisture issues. I also plan to add some cladding (maybe 1/2 to 1 inch on the dome) then wrap with a ceramic blanket at about 4-inch thickness to help with heat retention.

Any other beginning thoughts or things that I may want to consider from other's lessons learned...before I get too far down the path?

Thanks to everyone that has gone before me for all the great information out here!

Bob

p.s. pics and progress to follow in the coming weeks.

[Gulf]

Hi Bob,

Welcome to the forum. 2" of foam glass is an excelent material to use under the CalSil. It doesn't wick moisture and it is also added insulation. I would not recess it in the concrete hearth. I would use it as a medium to elevate the CalSil high and dry above the hearth. The drain holes in the hearth are still a good precaution. UtahBeehiver (Russell) used foam glass on his build. I don't think that he recessed his. Any thickness that you add to the oven will also be added in some way to the entry and possibly the landing. It will not look unproportionate when finished. You are correct in considering the finished floor height while planning the oven stand.

Since you are mostly interested in bread baking, you may want to think about orienting your floor brick to have a 4.5" thickness. That may not be necessary if you don't plan on multiple batches. Maybe some of the bread folks will jump in here on that.

[SableSprings]

Welcome Bob! Joe pretty much covered what I would have suggested. My only comment on the proposed build is that the cladding between the dome and the insulation doesn't seem worth the effort. The added mass would not be that significant (IMHO). I do primarily bread baking in our oven and have pitiful insulation compared to your plan. My oven is 39" ID with about 5"-6" of 5:1 perlcrete for base insulation and about the same thickness of 10:1 perlcrete for my dome insulation. And yes, with your plan you won't need any vermiculite or perlite below your foamglas.

I bake every week and put through 15-25 loaves each firing. I usually make 400 g (dough loaves) as my baguettes and 650-700 g dough loaf whole grain breads. Normal count is 14-18 baguettes and 4-6 of the larger whole grain bread. I fire up the night before, with a possible small fire in the morning, and bake generally around 2-3 in the afternoon. My main issue is simply fitting & working the loaves in the oven. Baguettes (6-8 per load of 66% hydration dough, baked at preferred 575F) and whole grain (4-6 loaves/load @ 64-65% hydration, baked at 500-525F). No problem with my heat for that bake amount, so the superior insulation in your oven would certainly allow you more loaves. My cooking floor bricks are just normal firebricks laid flat (2.5" thickness). My only issue with heat sometimes is when I have overheated the chamber and it's warm outside...I can't bring the temp down very quickly. If my dough is ready to go in and the oven's too hot, I've got to bake on inverted sheets until the cooking floor cools down .

How large of an oven chamber and how many loaves are you planning per bake? I certainly don't have any problems with my oven spring and only use a pump-up mister for initial oven chamber steam. We never had a follow up on any of the "steamer additions" posts that I remember, so I'm not really convinced it's worth the extra effort. You get quite a boost of moisture in the chamber with a good load of dough and a couple good shots of water with the mister. It's really only to keep the dough skin from setting until after full expansion of the crumb or to give it a shinier crust (which I consider a bit tougher and not in my goals).

Good luck and looking forward to your future posts. I hope this info helps.

[ConstantBuilder]

Hi Gulf and SableSprings. Thanks for the welcome and your thoughts on my approach. I will probably keep the floor bricks flat on the surface, I am thinking the insulation will be enough for the heat retention and I won’t have to heat up extra mass from the bricks being on their sides.

And Sable, thanks for the information on the bread baking. I am shooting for 15-20 round loaves per baking if possible. It is good to know that the moisture content in the oven is sufficient with some help from the mister as needed.

I hope to get started next week. I am planning on going with a corner build to fit in with my existing patio. I am ordering materials tomorrow then the fun begins!

[UtahBeehiver]

The steam injection was done by Faithinvirginia, unfortunately for us, she does not participate in the forum anymore, much to the members loss. She is a master bread maker like Mike. Here is a link to her injection post.

https://community.fornobravo.com/for...injection-test

[ConstantBuilder]

Thanks for the link UtahBeehiver. I have been going through your build and the details have been very helpful. I am planning on the corner build also, do you happen to recall your base dimensions? I want to make sure I have enough room for the landing. The original Pompeii plans don't seem to allow for much room for the landing for the oven opening.

Thanks again!

[UtahBeehiver]

Im out of town for a few days will pull my notes when i get back. Just to make sure, are you talking the concrete pad or the cmus

[ConstantBuilder]

Thanks. I meant the pad mainly, but if you have the CMU base measurement, that would be great too!

[ConstantBuilder]

I picked up the block and firebrick today and metered concrete is coming in two days. CalSil and FoamGlas should be here in a few days also. Getting the site prepped today and tomorrow. I am planning on a 6" base slab and a 3.5 inch oven floor supporting slab (please let me know if this is an acceptable thickness for the upper slab?) I will have extra CalSil insulation above this slab, so no need for the thicker vermiculite slab. I am ending up with a 82" x 82" x 51" x 51" (shorter wings) corner slab to fit the 42" oven and leave room for a wider hearth leading to the oven opening. I used SketchUp to mock up the slab and base and it all seems to fit well with the 51" outer diameter oven. Any last minutes thoughts before the cement starts flowing? I have a few pictures coming, just need to get them off the phone.

[UtahBeehiver]

I PM my dimensions earlier today.

[ConstantBuilder]

Thanks for the measurements UB!