baking expert seeks oven expert. MHGSOH!! Introductions Discuss baking expert seeks oven expert. MHGSOH!! in the Good Background Information forums; Another idea, if you build the dome/iso/hearth inside of a pan like structure you might be able to use air ...

[n2iko]

Another idea, if you build the dome/iso/hearth inside of a pan like structure you might be able to use air bags to dampen the vibrations. Deflate the bags to use the oven and pump it back up to travel.


--mr.jim

[michaelthebaker]

thanks for all the positive advice. will be speaking to forno bravo about a precast oven but they are in segments and i wonder hwo they would perform on a trailer. we will see. i would really prefer to build my own. anyone one know about these silica fibres or stainless steel needles that could be added to the cement to give it strength. i'll continue with the planning stage. later.

[edschmidt]

I just checked the castable refractory which I used and it has a modulus of rupture of 2000psi. With one caviat, it must be brought to 2950degF to reach this strength. Even at 2500deg. the modulus is only 500psi. What is the modulus of normal concrete?

[cvdukes]

>>I'm a little concerned about the re-inforced concrete idea. Regular mesh/re-bar re-inforcement isn't used with refractory concrete because of the large temperature variations in ovens: the big difference in co-efficients of expansion between the masonry and steel can set up stresses and cause cracking and failure. Cast refractory is re-inforced with stainless steel needles.<<

When I mentioned ferro-concrete...I was not thinking of refractroy cement and stainless steel.... My experience is strictly with normal ferro-cement made with standard hog-wire fencing, chicken wire and masonary topping mix cement. Maybe I got lucky when I made my pizza oven this way but I've fired it up to full temp at least 10 times now and haven't had any indication of cracking anywhere in the dome. Last weekend, we ran 14 pizzas through it during an oyster roast party. I could have cooked several more, but everyone was full from the oysters too. Thats on top of our temps swinging widely... had a low of 16 F the day before the party. Normally I'm at cooking temp in an hour of firing but it also took longer last weekend because all my firewood was wet when I started and I was more occupied stoking the oyster fire.
I've rechecked my construction costs and now think that I have a total of $63in materials in the actual pizza oven dome. Since cost is an issue, I would sure try to replicate my success with your mobile oven. Figure the worst you'll be out of is less than $100 if it doesnt work, but I pretty sure it could take the vibrations of a mobile oven.
Just to repeat how I did the pizza oven (see my post on newbie intros)...the shell was 3 layers of 1 inch mesh chicken wire over hog wire fencing (picked up off rubbish pile at no cost), hand-packed with topping mix and kept moist during a week long cure. After that, handpacked unfired stoneware clay inside the dome...couple of days of air-drying during which the clay cracked something fierce. So covered clay with layer of fiberglas reinforced concrete Then since I didnt want fiberglass fibers flaking off into my food, I did a thin layer of portland-fireclay-sand-powdered kaolin.
My oven floor was a single pour of the portland-sand-fireclay-kaolin mix to about a 3 inch depth. Now I do have slight crack in it because it has no reinforcement and probably did not cure long enough before I starting firing the oven...but nothing major.

[dmun]

This is interesting to know. Our refractory ovens are way overspec for our under 1000f temperatures. Ceramics people build kilns exactly like ours (firebrick with refractory mortar, wool and cal-sil refractory insulations) in similar thicknesses, and regularly fire them up to orange heat.

The pompeii plans have long said that you could use plain red brick if that's all you could get. Folks in Australia where fire brick is expensive and hard to get have built such ovens successfully.

If a plain concrete dome with chicken wire reinforcement will work fine, it's good news for our builders on tight budgets. I found that the insulation was more costly than the dome materials, so I don't know if it's that much of a overall saving.

This is just me, don't beat me up or anything, but I think a brick oven should be made out of brick. I love sliding a pizza onto that herring bone pattern floor.

[cvdukes]

With my construction method, I would agree about the costs of the insulation except I found a vermiculite mine just over an hour away from me and was able to buy it at wholesale (~$1.25 per cubic foot). Of course I had to buy a large quantity but I'm using to insulate the bottom of the pool and making a few roofs with it too.

Oh, my infared thermometer goes off-scale at 1024...don't know that it is super accurate at that range but I always fire til it reads "High" so my ferro cement is going up at least above a 1000.

But also have to admit that the pics that ya'll post of the herringbone brick patterns do look really nice and it would be cool to have that pattern on the bottom of the loaves!

[Frances]

You're lucky in the US. My bricks cost around 800 USD - and this was for non-perfect ones that I was able to get cheaper...

Actually when I was looking for plans for an oven on the internet, the first site I saw was in German, and it has a pizza oven made of cement:

Projekt Steinbackofen/Pizzaofen (Bauanleitung) | majoo.net

Those peolpe seem happy with it, too, so it does seem to be a viable alternative.

But having said that, I'm still very glad I found this site before starting the oven!!!

[asudavew]

I didn't think concrete would work.
I'm impressed.
Now I am thinking of building a much smaller oven out of concrete.
That way I could have much faster heat up times and compare the two.

I guess I have a summer project now!

[edschmidt]

Ive seen enough firepits surrounded by concrete retainingwall blocks to know that they crack and prettymuch disintegrate within 6 months. Some fireclay added would help, but long term, I have doubts.

[asudavew]

Originally Posted by edschmidt

Ive seen enough firepits surrounded by concrete retainingwall blocks to know that they crack and prettymuch disintegrate within 6 months. Some fireclay added would help, but long term, I have doubts.

Fireclay!
Good idea!

It will be fun to give it a try.

And not much involved so......