Oven dome material

[Hafsteinn]

Hi everyone!

I'm new here and i want to start a build on my first oven. The problem is however that I live in Iceland and I can't find anyone selling refractory cement and only one company sells firebrick and they are expensive to say the least! It is also impossible to get clay around here other then in very small batches.

So my question is.. Can I use any other material to construct the oven dome?

[ooed3m]

I am really into brick ovens. The first thing that is important is to build a round oven, with a spherical dome. It is efficient with wood, heats up fast and puts even heat down on your pizza. The next time you are in a wood-fired oven pizzeria, look in the dome -- it's very fun to watch the fire dance in the curved dome.

There are two types of dome height. The Naples oven is lower, while the Tuscan ovens are higher. The Naples style is said to be better for pizza, while the higher dome better for bread and roasting, but both really work well.

A front opening and vent is traditional, and works best.

[wotavidone]

Iceland - volcanic rocks , correct? As in igneous rock.
Can you get rock/stone easily? Dense stuff for floor and dome.
Scoria or pumice for insulation?

Edit: Further research suggests igneous rocks like granite bdon't do well with thermal cycling.
Might do better using some sort of sedimentary rock.
But, ovens get built from rock. even if it might be a bit of a challenge finding the right ones.
Research suggests it is of questionable legality to harvest your own rock "from the wild" in Iceland, but there must be quarries?

If pumice is available for the insulating layer, I envy you.

[wotavidone]

As for mortar, hmmm. The old Greeks and Italians in my neck of the woods leave out the fire clay and use 6 sand, 1 Portland cement, 1 lime.

[Hafsteinn]

Thanks for the reply wotavidone.

it is possible to get sedimentary rock here, but its very expensive. I might check that out though.

We have a lot of pumice here and its very cheap. Should I mix that with cement and apply directly to the dome for insulation? 1:5 ratio perhaps?

[wotavidone]

Probably 5 or 6:1 under the floor, maybe leaner over the top of the dome. (I reckon DavidS suggests more like 10 or 12 perlite:1 cement for over the dome.) Under the floor you require some structural strength, over the dome it only needs to hold together, not support the weight of an oven.

Your situation seems unique. Apparently a material called soapstone is the bet for tolerance to thermal cycling.
Google it you'll see it is sometimes used as a fireplace liner. Soft enough to carve so it might wear quickly if used as a floor.

Granite breaks down under heat, they say.
Basalt is used as an aggregate in high temp concrete but might spall if used in brick like sizes.

Has to be a way though - looks very rocky in photos on the web, just a case of working out which rock to use.
Is there a very old Icelandic person you can speak to who might have some cultural memory of how things were done back in the old days?
It looks a bit cold in the photos I've seen, Icelanders probably had to build fireplaces and things before man made bricks and refractory mortar came along.
Has this stuff ever been used in a fireplace - helluhraun? Also known as phoehoe

It's all a bit of an experiment.

[wotavidone]

Lava rock is looking good:
http://www.pacificgunite.com/pizza-oven.html

Watch the video

[UtahBeehiver]

Wow, that is interesting lava oven, all hand made dome and floor bricks no wonder it costs $7500. My family is from the islands, although I am a mainlander, and everything cost more but not like what our downunder brothers have to pay for materials.

[wotavidone]

Yes, $10,000 Australian had me gasping for breath.
It is a very well built oven, but Hafsteinn would possibly want to pay a little less, I'm guessing.

Anyway I posted it because it seems to confirm that if you live on a volcanic island you can use lava rock to build an oven, Refractory products being almost non existent in Iceland, you wouldn't be making a thin shell dome and coating it with refractory. I'd say they probably do that to make it more robust for transport.
Rather make the dome 3-4 inches thick with lava rock and a mortar of sand lime and cement, and a floor of basalt. Insulate the whole lot with pumice, I'm envious, and Bob's your Auntie's live-in lover.

Disclaimer: I've never built anything from lava rock. It would be good to rig up something just cobbled together and light a fire in it just to make sure the rock is going to work before all the effort of building a full oven.

[Hafsteinn]

Its very easy to acquire lava rock here and Helluhraun is no problem to come by. I was just so caught up in using the same materials as most people do that I forgot to look around me and see what we have here.

I'm going to investigate the lava rock option better and see if I can use that. Could probably use regular firebrick for the floor, Ytong bricks (I have a lot of these http://www.ytong.gr/) for sub floor insulation, lava rock for the dome and pumice for dome insulation.

I'm a bit concerned about the lava rock for the dome as it is very "airy" and would probably be a better fit for insulation rather than thermal mass

Sounds like a plan?

[wotavidone]

Airy? hmm, no good. For the dome, you need at least 2.4 density, in my opinion. i.e 2.4 Kg/L, 2.4t /m³ etc. Like a firebrick. There must be a rock that meets this. Basalt?
I dunno. Ain't no volcanoes where I live. Find a dense rock. Must be one somewhere.
Ytong is equivalent of our Hebel. People say it is no good because it is made with Portland cement, then recommend "vermicrete".
"Vermicrete" is vermiculite with , you guessed it, Portland cement.
Anyway, think heavy solid high density blocks for dome, aerated low density stuff for insulation, and I'm sure you'll find something.
The tough question for me, who has never lived in an area with volcanic rock is , "define lava rock"
There seems to be some dense, some aerated.
There must be something that flowed out of the earth that is dense?

[wotavidone]

Having trouble leaving this one alone. i'm a product of my upbringing I guess. Way before the back-to-earthers made it trendy my old man was always finding ways to repurpose, reuse, etc.
So I'm always looking for alternatives. Sometimes sets me back, sometimes saves a little money.

Back to the problem of building an oven in Iceland, which seems to have an abundance of rock.
Further research suggests "lava rock" is a bit of a catch-all term, that includes the sort of of lavas that contained lots of gases and are pretty much solidified foams.
I guess you need to find a type that didn't foam up when it soldified.
Avoid granite as it's considered likely to break down at the surface when exposed to the fire.