Rustic Primitive Materials

[Annie M.]

..........

[brickie in oz]

Re: Rustic Primitive Materials

I am wondering do I need to infill with beach sand (that is what I would use) to help insulate the bottom of the oven?

Sand is not an insulator, it will conduct the heat away from your oven into the base.

I have plate of 1/2 inch thick cast iron that is 3' x 5' that I was planning on placing on top of the rock base as a platform for the firebricks for the oven... my reasoning was that the cast iron would provide heat retention & stability... is this a good/bad idea?

Again, all the heat from the oven will escape through iron/steel and brick into the base, you need to insulate.

[wotavidone]

Re: Rustic Primitive Materials

Hi mate.
I applaud your decision to go with what you have.
Here are my thoughts:

1) Rocks might be heavy but, unless you are a very short person, trying to cook in an oven with a floor only 2 feet 6 inches off the ground will be a pain, too.
2) Find some insulation to go under the floor bricks. If you use your oven, and then decide it needs insulation over the outside, it's very easy to add later, and can be quite cheap. For example your insulating layer over the outside could be clay with sawdust in it if you were really short of cash.
If you build your oven with no insulation under the floor bricks, adding it later is next to impossible, so it's much better to "bite the bullet" and do it now.
Is a layer of vermiculite concrete beyond your financial reach? This would be good, as you can "screed" it fairly flat.
Perhaps you can get scoria or pumice? Essentially you need either something that traps air, which is a poor conductor of heat, (pumice, scoria, vermiculite, perlite) or a material that itself doesn't conduct heat well (ceramic?)
3) Most people say red bricks are probably not as good as firebricks, but thousands of ovens would have been built with them, and many have lasted decades, even centuries. Advice from a brickie - most bricks have been fired at least a bit hotter on the surface than inside, so make sure that an original outer surface is facing your fire - it will be that little bit more robust.

I know a guy who has an oven made of red brick (dome) and fired clay pavers on a sheet of steel for the floor. His advice to me was "Don't worry about insulation, these things get bloody hot."
The difference between his and my moderately insulated oven is that his takes well over two hours to get to pizza heat, and presumably takes a lot more wood.

So insulate if you can, but if you can't build it anyway and be prepared to accept it will be slower to heat , and hungrier for fuel, and you may never get a 90 seconds margherita out of it.

All the best with your build.

[wotavidone]

Re: Rustic Primitive Materials

PS check you red bricks. Make sure none of them have gone soft or crumbly. You should be able to tell when you cut them.

[Tscarborough]

Re: Rustic Primitive Materials

Beach sand contains salt so it should not be used for any kind of construction.

[Laku]

Re: Rustic Primitive Materials

Ceramic is an interesting idea... perhaps I can put something together from a potter friend's shard pile.

As far as I know not an insulator, unless in fiber form (ceramic blanket or board)

[Laurentius]

Re: Rustic Primitive Materials

Hi Annie,

Here are the plans for a modern(meaning well insulated and fuel effficient) traditional pompeii oven. Look at it and see how you can modify it to your needs. Keep it Rustic Primitive, but make it function as if solar powered, go with ceramic fiber boards and blankets, since this wil be your only real expense. Good luck and in a few months, start sharing your recipes.
Pompeii Oven Plans2.0

[wotavidone]

Re: Rustic Primitive Materials

As far as I know not an insulator, unless in fiber form (ceramic blanket or board)

Ys, I should have been clearer - ceramic fibre or blanket is what I meant.
That's a beautiful door by the way, you certainly must incorporate it in your build.

[Laurentius]

Re: Rustic Primitive Materials

Hi Annie,

We didn't think that you would be picking ceramic boards and blankets from your friend's shard pile? That door looks great, but HEAVY, and it will get HOT and you need handles. It might be better served as a rustic plaque?

[brickie in oz]

Re: Rustic Primitive Materials

I made a little progress today... I hope.

I was able to acquire some new firebricks at what I hope is a reasonable price (1.25/1.45) for split and full bricks. However they were just on a pallet with no manufacture identification but I jumped in anyway and purchased some.

The splits weigh 3 lbs 9.5 oz & the full bricks weigh 6 lbs 8 oz does this sound like the correct weight for the type of brick usually used for the oven floor?

Fingers crossed... Annie

Sounds good, the heaver the brick the denser it is.

[brickie in oz]

Re: I have a plan!! ...almost

a prototype dome using angle iron for supports to test the design and see how it holds heat before I do anything permanent with mortar.

The steel will buckle with the oven heat.

[wotavidone]

Re: Rustic Primitive Materials

Annie,
Have your read the plans that Laurentius posted yet?
I ask because, even if you don't actually follow them, they give some good guidance on the basic dimensions and concepts.
There is a need to balance the amount of thermal mass in the dome against the mass in the floor.
I'm a bit concerned about your intention to have a layer of cast iron topped by two layers of brick. I am interested to know how thick that would make your floor compared to your dome.
Most builds seem to have a single layer of full thickness fire brick for a floor.
The floor is heated mostly by reflected/radiated heat from the dome, and if there is too much mass compared to the dome, you may end up with a large temperature differential.
What do more experienced builders think?

[Laurentius]

Re: Rustic Primitive Materials

Hi Annie,

Yes, you can mud cover your bricks or even go totally cob. But now it seems as if you have community interest and offers to help, If I were you, and I have been you in respect to my oven. I would build the most efficient oven I could and the first concern after size would be insulation. A well insulated oven will allow multiply uses during the week without having to use more fuel with little or no maintaining. Three(3) inches of ceramic blanket is recommended for the dome and two(2) inches of ceramic board for the floor. I see the wheel spinning in your mind saying,"What the hell am I getting myself into"? It will take about the same amount of time to do something (half-assed, something my mother used to say to me) as it would to do it right. If you are having doubts(don't do anything for a while, thing about it). Word of caution: Take no advice from Cob Ovens Builders, if they mention glass, sand, mud-straw or fiberglas as insulation for an oven.

[deejayoh]

Re: Rustic Primitive Materials

Annie -
fellow NW builder here. Take a look at mcgillswarehouse for your blanket and insulating board. You can insulate top and bottom for ~$200. Rustic ovens are cool, but insulation is really the thing that makes modern ovens so much better than roman ovens.

[Laurentius]

Re: Rustic Primitive Materials

Annie, once its up and running, you will forget about pizza, you'll be thinking, breads, stews, casseroles, bake potatoes, dried tomato, baked hams, candied yam and sometimes peanut butter and jam-----------pizza. Dream on, make your dream come true.