An all-firebrick oven

[Brock]

Suppose you could get firebrick really really cheap. How much mass would you want around your oven before you felt you had enough? Does firebrick hold heat better than sand? Better than common brick? Suppose you could get firebrick cheaper than common brick; would there be any advantage in building the whole oven from firebrick?

[mn8tr]

Fire brick is very porous and would soak up a LOT of moisture. Also there would be nothing to stop the heat from working it's way out rather than holding it all in.

[GianniFocaccia]

It would be wise to read through the Forno Bravo Pompeii oven plans before proceeding. The construction materials for the base, oven and insulation and their respective dimensions and properties are all covered in great detail. The only really significant variable is how much time and attention to detail (craftsmanship) you want to invest in making your design and finished oven unique.

[Wiley]

Here's a link to a WFO close to what you are describing:

Jefferson County Man Bakes Big With Brick Oven » Kitsap Sun

I've seen this WFO and feasted at a couple of Phillip's parties. If I remember correctly his WFO is 17 inches thick and solid brick. Takes a bunch of wood to heat (and time to heat) but wood is not a problem where Phillip lives.

Please note: I insulated my WFO as did John Shelley (mentioned in the article, who also has a WFO). Even if wood is free and plentiful I think insulated is the way to go.

Bests,
Wiley

[dmun]

How much mass would you want around your oven before you felt you had enough?

Exactly the amount suggested in the pompeii plans: 2 to 2 1/2" in the floor, and 4 to 4 1/2" in the dome. This is the amount of thermal mass proven by much experience to be the ideal balance between a reasonable heat up time, and adequate heat retention. More mass means wasting time and fuel, Less mass means a significantly weaker structure.

Does firebrick hold heat better than sand?

Yes. Firebrick is a refractory material. How and why would you use sand as your thermal mass? It doesn't make any more sense than the occasional notion to use sand as an insulator.

Better than common brick?

Yes. Firebrick is a refractory material. Some people build their domes out of common brick if they live in places where they can't afford firebrick.

would there be any advantage in building the whole oven from firebrick?

The whole thing? From ground to chimney top? That wouldn't make any sense, aside from being an oven without insulation. (This is a completely unworkable idea.) You would be much better off selling the excess cheap firebrick at a profit, and buying the proper materials.

[Brock]

So I ended up getting some firebricks that were key-shaped with angles to make the arch (I'm building a barrel vault). The roof is 9" of firebrick. The people I've talked to who have used this brick say that it holds heat extremely well, and it stays hot for days after. So thermal mass, solved, now to the insulation...

[GianniFocaccia]

Have you checked out the Alan Scott design for barrel vaults? I'm a Pompeii kinda guy, but the AS ovens are so beautiful, if I could get firebricks really cheap I would seriously consider building one, just for bread.

[Lburou]

Originally Posted by Brock

So I ended up getting some firebricks that were key-shaped with angles to make the arch (I'm building a barrel vault). The roof is 9" of firebrick. The people I've talked to who have used this brick say that it holds heat extremely well, and it stays hot for days after. So thermal mass, solved, now to the insulation...

9 inches of mass is fine as far as heat holding performance goes (assuming you insulate)....Did you understand the significance of what dmun said about heat up time?

You will be hours (perhaps three or four hours) heating that 9 inches of mass each time you fire your oven, assuming you insulate it. without insulation, you may never get it hot enough for 90 second pizza....That would be a show stopper for me

Great find with those specially shaped bricks!

My advice about getting smart about building wood fired ovens is here. (A newbie’s survey of the Forno Bravo treasures hiding in the archives) I was planning to build a barrel oven. After looking around on fornobravo.com, I changed my mind to reduce the unknowns in a build by a novice. Happy with my decision to build the standard pompeii oven.