My attempt at an oven

[Devo101]

If I can figure out how, I will post some pictures but here is my "design" and attempt at an oven. Built on my pool patio so I did not dig any footer.

Two layers of cinder block as base - about 20 inches from ground
Used concrete pavers to give me flat surface on cinderblock base
Bought 24 fire bricks and used them to build oven base on pavers
Built up with standard solid bricks for sides of oven - 1 brick thickness (everything dry stacked so far).
Made a roof using fireclay/sand mixture and a homemade 2"x4" form about 2 feet by 3 feet by 2-4 inches thick. Used a concave disk to make "dome" on underside of formed roof. After curing for a couple weeks flipped it over and set on top of dry stacked bricks.

Took roof off and mixed a sand/fireclay mortar. Put a layer on top of drystacked bricks and reset roof so it is sealed.

Used mortar to set a second layer of bricks on all sides thereby adding mass and sealing oven interior.

Dry stacked another layer of bricks on roof (these bricks are concrete bricks not clay bricks - but cheap).

About $200 in project (I looks sturdy but not very pretty - I am not a mason I can tell you). About 2 days all told laborwise.

Fired first time last weekend. Fire burned nicely - for about 2 hours(start to finish). Started small and moved to oak chunks and pushed to back. Top was very hot sides not so much (outside that is). No smoke to speak of seeping from oven. A crack developed in roof but does not appear to be a structural issue yet.

So I used my kitchen thermometer and got about 450 in oven after raking out fire (using bricks drystacked as "door"). Want to get one of those lazer heat guns.

Went ahead with bread - bread got about 2/3 done in about 1 hour and I had to transfer to indoor oven to crisp it up and finish it. But it did get great oven bounce and ended up tasting great.

About 10 hours later interior was still about 250 - top was warm and sides were as well (about equal heat this time).

I suspect I may have to build a brick roof ultimately - but nothing ventured nothing gained. I also think I may not have fired oven long enough to get a good bake out of it. I am going to try to fire it longer and with a stronger fire this weekend.

If that does not work (and roof still looks ok), I may try to mortar real bricks on the roof top to absorb/store more of the heat (similar to the sides). Finally, I may have to insulate the whole thing somehow.

Any thoughts/advice or predictions?

[aliza]

Re: My attempt at an oven

nice post
thanks

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[dbhansen]

Re: My attempt at an oven

A picture would help, Devo. And it sounds like you could definitely use some insulation. You'll be able to achieve much higher temps and hold it there longer.

[Devo101]

Re: My attempt at an oven

So I am going to try to post three pictures. Any suggestions on what to insulate with? (Note: third picture to come in next post)

[Devo101]

Re: My attempt at an oven

Here is the third. You should be able to see the crack in the top in one of the other pics. It does not (so far) seem to be threatening the structural integrity of the top (it is tied into the sides with mortar and supported on three and a half sides. However, I do not want to go permanent with insulation yet since I may have to take top off and rebuild using bricks in an arched roof type setup. What about foil wrapping? Will that help? If I do replace the top with bricks, do they have to be fire bricks or will solid red clay bricks work as well (I suspect I know the answer but just asking).

[dmun]

Re: My attempt at an oven

Made a roof using fireclay/sand mixture and a homemade 2"x4" form about 2 feet by 3 feet by 2-4 inches thick. Used a concave disk to make "dome" on underside of formed roof. After curing for a couple weeks flipped it over and set on top of dry stacked bricks.

This is very interesting. We've heard of the sand/fireclay mixture being used for mortar, but never for a large cast element like this. I'm interested in how it holds up. Did you mix the two in even amounts? (50/50)

And yes, your oven will never do much of anything if you don't insulate it. If cost is an issue you want to use vermiculite/perlite concrete. Since your oven is not mortared together, you should consider dismantling it and putting four inches of the vermiculite mixture underneath the floor, as well. Nothing will make your oven work better, faster, and more efficiently than insulation completely surrounding it.

Another thing to consider is that your fireclay/sand dome must be kept completely dry. It will collapse if it gets wet. You will want to think about some kind of roof over your oven.

And the layer of concrete "bricks" on top of the dome? I don't see any point in that. Also, the use of foil around oven has been completely discredited. Don't do it.

It's looking good for a quick, low cost project.

[Devo101]

Re: My attempt at an oven

Thanks Dmun,

I have a couple questions. Do I mix my own vermiculite/perlite concrete? If so, is it 50% v/p and 50% portland cement?

I am surprised you are recommending covering the fireclay/sand mortar top as it is hard as a rock - the fireclay has portland in it so it is basically a cement slab with fireclay mixed in is my understanding. I figure if I am going to have to cover it, I will just get a supply of excess potters clay (local source) and mix with sand (maybe straw as well) and make a domed roof with brick sides to replace the cracked slab I currently have (easier than masonry work).

That being said, I AM going to have to replace the slab as it is cracked in four. Still structurally sound but not looking good for the long term (especially is I have to cover it). I will try to take a picture so you can see the cracking.

Anyway, baking bread inside in oven today - back to drawing board on outside brick oven.

[azpizzanut]

Re: My attempt at an oven

Hello,

I'm happy to see you so involved in your oven project.

I'd like to recommend that you do a Google search on Perlite. There is much information on mix design using Portland cement and Perlite. You can use one part Portland to four of perlite and an even lighter mix might be 1 to 8. It is insulation and not structural, so no need to go too heavy on the Portland.

You might also gain insight on your oven heating/retention by searching on Pizza Oven Design (or bread oven design or wood fired oven design). A door opening height roughly 63% of the inner oven height will help to heat the structure instead of letting heat directly out the opening. Can you visualize that? There is a lip or overhang from the inside that the heat has to negotiate on its way out. Otherwise, the heat has a straight shot the front of the oven. Also, look at a common horno, cob or adobe oven for some insight. The dome inside is higher than the door opening. Same objective.

Best of luck to you,