I've got a bunch of ceramic tiles kicking around, and wondered if I could put them to use to build an earth oven; that is, build the walls and ceiling using ceramic tiles (600mm by 600mm) to create a box-shaped oven. I found some terra cotta tiles (unglazed) that I thought I'd use for the floor. I then thought I'd encase this cube in a layer of clay/cob. My question is - would this actually work?
Does the ceiling have to be barrell-shaped? Can it not be flat, as found in a cube or, as an even better example, the oven we use indoors? I've had only a tiny experience building a rocket stove, but observed how much the vortices from the fire seemed to love hard corners and ninety degree turns. Has this ever been observed in earth ovens?
Over this oven I thought of wrapping a rockwool blanket, before slapping on more clay/cob to finish? Much thanks for taking the time to give this a thought. Any ideas much appreciated.
G'day Of course a cube shaped oven will work as you have pointed out a modern domestic oven is a cube. The best example I've seen work is the dry stacked brick ovens with angle iron to hold the entrance and oven roof up. But you find that all the traditional shapes the circular Pompeii type, the pear shape and the tunnel all have a curved surface. You operating on radiated heat so there better at throwing that heat back to the cooking surface evenly. With the tiles they are not the best choose for a wood fired oven surface. They are baked hard to be a hard wearing surface . But they do not take to being heated and cooled and will crack in a short time . Brick is softer but will handle the heating and cooling cycles a lot better , of course firebrick is best. By rockwool I'm taking that you mean domestic insulation. The glass fibres themselves are formed over 1200 C so they are all right but it's the plastic binders that hold it together that will cause the problem. Stinky plastics and possible poison smells. Not good with food. Nows there's a disclaimer there ... I have used rockwool in my oven ove. 2 ins of ceramic fibre insulation first so it not effected by high heat. So I'm sorry to put a damper on some of your plans but why not a dry stacked brick oven ? Or go a bit traditional and do the clay oven with the cow shit/hay/sawdust insulation? Regards Dave
Hey cobblerdave. Thanks for the heads-up on dry baked ovens . I like very much.
Before I dump all ideas of using tiles, it remains that I am still abundant in unglazed terra cotta tiles - are these any good? Could they be used in some way to act as a liner for the fire chamber? Would these tiles stand up to being the ceiling?
I also had some thoughts about an insulator. If not rockwool - what about air? I thought about surrounding a dry baked oven with empty tin cans (empty that is but for the all important air!) before adding a slap of clay/cob over the top. I had some luck trying to create an air gap to act as insulator when I tried my hand at trying to make a lightweight rocket stove. (By the way, it reminds me of a guy whom went the whole hog and designed his own rocket stove insulated by a vacuum!) Do you know of any examples of where earth ovens have used air gaps as an insulator?
By way of reasoning, I imagine that's why stuff like straw is added to the cob is to help generate air gaps - is that about right?
Oooooh. I found this site offered a pretty straight-forward explanation about air as an insulator...
"Insulation is a material used to slow heat loss, to slow the movement of heat from one place to another.
Most insulation uses air as a key ingredient. But to be really effective the air must be prevented from moving around. Examples of types of insulation that do this are foam and fiberglass insulation. Foam insulation surrounds little pockets of air with foam, and fiberglass surrounds it with small glass fibers."
I wonder if convection is really such a bad thing if I did create an air gap?
Okay. I got really excited about this design for a rocket oven. Me thinks it could be the thing for me ! ~ link
I guess that saves me a job on trying to line the entire oven with clay tiles - only now I have to think about where on earth I can find a mild steel baking chamber! I wonder if I could remove the baking chamber from a scrap oven?