brickless dome on a shoestring oven

[cynon767]

Re: brickless dome on a shoestring oven

Congrats! It looks like it's going great. I'd still keep an eye on the dome in the future, but it looks like you probably are going to be fine. I didn't get any cracks until about the 3rd or 4th big fire; but I'm fairly confident in my dome's ability to stand up at this point. I think you should be as well. So far, so good on the experiment with the homebrew refractory... keep us informed about it's longterm performance!

[michelevit]

Re: brickless dome on a shoestring oven

New Years Pizza party was a huge success. Cooked many pies. The oven has since had
several 'scary' fires and no signs of failure. I would recomend this method of construction to anyone building an oven. It was low cost and quick to build. No tile saw or brick cutting needed . The sand form worked great and built a perfect dome. The oven heats up in less than an hour and 90 second pizzas were not a problem.

brickless dome oven gallery here...Gallery | bricklessoven

[Lburou]

Request for Status Report

Its been about 20 months since you finished your oven....How is it doing after that much time and use?

[michelevit]

Re: brickless dome on a shoestring oven

Oven still working great. Just had a huge all day party 2 weeks ago. Cooked maybe 50 pies. One of the guests was pizza chef and he was impressed by the oven.

Still no cracks in the dome. Oven working great and makes great pizza.
Let me know if you have any other questions. I'm actually building another oven based on this design.

[stricsm]

Re: brickless dome on a shoestring oven

Do you have details on the mixture ratio for your high temp mortar (%fireclay, %cement, %sand, %lime)? I'm weighing costs right now and your approach sure looks attractive. Do you think it could be done without the rebar cage or using metal mesh (1/4") instead? Thanks.

[michelevit]

Re: brickless dome on a shoestring oven

The mix I used is the high temp mortar mix which is
One part Portland cement
One part lime
One Part fireclay
Three parts sand.

Mix well dry and slowly add water until it is saturated enough to be wet.

I wouldn't skip the rebar. I think it adds substantially to the strength of dome structure. Rebar is cheap enough. We used a simple angle grinder to cut the rebar to short lengths and mig welded it with a gasless 110 volt wire feed gasless welder. The rebar was done in less than one hour with three people helping.

I was anticipating cracks as the oven aged and believed that the rebar would hold in the broken pieces. So far no cracks!

[robertjusher]

Re: brickless dome on a shoestring oven

HI
I am really thinking making my build the same, just a question. Is the home brew mortar setting as hard and as long lasting as brought castable? And do you have any current photos to show how a few years have gone?, any dressing up of the oven etc
Thanks
Rob

[david s]

Re: brickless dome on a shoestring oven

A sand mould is not difficult and getting the form right is simpler than you would think. Here are a couple of tips.
1. Cut a stick to the exact internal height you want the dome to be and place it in the middle, then pile the sand around it .

2. Use moist sand (10% water if you want to be really fussy)

3. Tap the outer surface with the flat of a trowel, eyeing the profile as you do this. It will become remarkably accurate.

4. Cover with strips of wet newspaper prior to "mudding over".

5. Chop up some sisal rope or add animal hair to the mix to assist water removal (it burns away leaving mini pipes that steam can find its way out.

[david s]

Re: brickless dome on a shoestring oven

While rebar reinforcing may seem like a great idea to increase strength, remember that heat will accelerate any corrosive reaction. I think rust will eventually prove to be the undoing of this idea in the long term. When rebar rusts substantially it increases in volume producing stress cracks in the refractory material. The standard reinforcing for refractory is stainless steel needles presumably for the previously mentioned reason.

[Archena]

Re: brickless dome on a shoestring oven

Um, I don't see any exposed rebar - why would it be at risk?

[david s]

Re: brickless dome on a shoestring oven

The material is porous so oxygen still gets in. from my experience with kilns anything ferrous that is not stainless steel rusts very badly, is accelerated by the heat and is the major cause of kiln failure.Door hinges fall off, frame disintegrates etc. If rebar worked in industry then it would be used in preference to stainless steel. However, I should think you will have no worries for at least ten years, so it is probably not an issue.

[Archena]

Re: brickless dome on a shoestring oven

Ah, okay. Thanks.

[SoCalBri]

Re: brickless dome on a shoestring oven

David, I was thinking about building an oven similar to this. If you think the rebar frame will rust, any thought on another material to use to help support the dome, besides stainless steel?. Do you think it will hold up without and reinforcement?

[david s]

Re: brickless dome on a shoestring oven

Maybe chicken wire, but again, being not stainless and the wire being thin it would probably corrode faster. I think zinc melts at around 400c so who knows how protective the coating would be after a number of heating cycles. It will stand up without reinforcement even if it cracks because of the dome form. How long it will last is anyone's guess. If I were trying to make a cheap oven it is exactly what I'd do. After all if it only lasted a few years it wouldn't be that much hassle to redo it. Castable refractory is very expensive and designed for temps way in excess of those we get to. Build one and let us know how it goes. I advised a bloke to use this recipe about two years ago and he is happy with it, so far.

[david s]

Re: brickless dome on a shoestring oven

Yeah, I would agree, but I've seen plenty of rusty reo in concrete and it wasn't subjected to the high heat we give it. Actually the corrosive gasses given off in kilns, mostly sulphuric are responsible for the corrosion in kilns. Not sure exactly what temp these are given off, but it comes not only from the glazes but from the actual clay as the chemistry is altered as the clay is heated. I've seen concrete paths with steel fibres close to the surface that have rusted and expanded forcing lumps of concrete like little crater marks about 40mm in Diam. All over the surface. These were embedded in the concrete but obviously not sufficiently deep enough to be free from oxygen. Refractory material is also more porous than normal concrete so this would be more of a problem with the extra oxygen available. Look I'm just guessing the effect here, but industry use stainless presumably because normal steel doesn't work too well.