dmun's 36" geodesic oven Pompeii Oven Construction Discuss dmun's 36" geodesic oven in the Pizza Oven Design and Installation forums; Good looking oven, and a pleasure to follow the posts. I have been watching for a while. I don't mean ...

[PizzaMan]

Good looking oven, and a pleasure to follow the posts. I have been watching for a while.

I don't mean to be a critic, but I would encourage you to carefully evaluate before enclosing the oven: A critical issue in masonary construction--of any type--is to avoid running faults or on-going lines from one row of material to the next. (I'm sure someone could explain this better than I.)

I constructed my Pompeii with little difficulty, but when I first fired it I found I made a mistake: about three of my cut bricks lined up to the degree that they shifted slightly, creating a small crack. It is nothing that will affect usage, and has not grown with use. But I was disappointed to see it shift somewhat.

As I look at our photos, it is apparent that you have "broken" all the masonary rules regarding runnng seams. I hope that I am mistaken, but I would be concerned that your hard work and ingenuity may work a little bit against you. At least consult with someone with more experience than me, and bring up to temp very, very slowly. Again, the engineering is great, except that the hexoganal pieces are actually several pieces, each with faults (where edges meet). It may not hold as well as one would hope.

Perhaps this is not an issue. But there are enough qualified builders here to offer some good feedback on this issue.

Best of luck and thanks for letting us watch!

Michael
aka PizzaMan

[dmun]

The picture you reproduced really shows that: an uninterupted mortar line crossing the entire oven. In fact the entire dome is an interwoven mesh of running seams.

Will it crack? Cracking is certainly a issue with homemade dome ovens. I remember one post here entitled "Enough with the cracking already" It's my hope that having closely fitted seams, and refractory mortar matched to the expansion of the firebrick will reduce or eliminate cracking. You just never know. Fio had a piece of refractory flue tile crack on him: You should be able to drop that stuff off a roof.

One precaution i'm going to take is have a slip plane between the door opening and the refractory assembly within, to avoid differential expansion. Another is to let it cure for a really long time: Because I'm building a two story, two flue masonry chimney, it will probably be next spring before I have it properly vented and build a fire in it.

Thanks for your concern. It's one I share.

[DrakeRemoray]

Originally Posted by dmun

I have a big piece of matching slate for that:
I know, not the best material, subject to staining, but it's here, and will complement the rustic look of the oven.

Sounds great. We don't call that staining...we call that "patina".

Drake

[dmun]

We had a stretch of great weather this week, so I took the time to go back to masonry.



First the slate. The big piece of slate that I had gotten to make my oven landing shelf cracked all the way through while being cut. Zut alors. I went to the stone yard and got a 12 x 48 bluestone step, and had them cut it down to the 40 inch width. Not cheap to buy, but the cut was free. I also got another little piece of the same material to make the arch pieces, since many of the arch stones I tried to make were fracturing when sawing. The piece in the center was sound, the original darker color, while the blocks on the sides match the shelf. It's a polychrome extravaganza. You'll be glad I passed up those bright pink marble tiles that HD has on sale for a buck apiece.



Here's the refractory inner arch pieces, cut to fit form,



and mortared together into a pre-fab arch.

[dmun]

Once on this forum, I saw a picture that someone posted of two flue tiles side by side sitting on top of the oven opening. They may just have had them stored there, but it gave me an idea:


If you cut an 8 x 12 flue tile on the bias, as drawn, you get,



Two pieces like this, which,



can be trimmed like this,



and assembled into a thing like this. It fits an 8 x 8 flue tile on top, and flares to 8 x 15 1/2 on the bottom. Cool, huh? Stay away from those pricy sheet metal fabricators. Warning, refractory flue tile is the hardest thing I've cut so far on this project, and the size of the thing means that the long cuts need to be made with a diamond blade in the angle grinder.

[dmun]

The pre-fabricated refractory arch is mortared to the ends of the flared entry walls,



But not to the decorative walls in front. The whole refractory oven assembly is designed to float free of the outer walls.



The gap between the refractory and decorative arches is going to be filled with mortar, so I don't get smoke leaks at the arch, but the inner arch is wrapped with aluminum foil to prevent the mortar from adhering the two together.



I had filled the gap between the flared entry walls and the exterior walls by mortaring in some triangle scraps of firebrick:

[dmun]

I start to build the outer arch:



The exaggerated keystone in:



A rear view:

[dmun]

In our spell of warm weather I got the oven up to the point where it's above the level of the hole I knocked in the exterior wall, so I can put up a temporary roof to close the workshop up for the winter. Some pictures with the forms removed, and the stone scrubbed:

[james]

Is that the coolest thing, or what. That beats Nick's assistants -- well, maybe.

David, are you thinking about a mortar coating to help hold those joint together through thermal expansion and contraction, or are you going to rely on the "mesh of interconnected seams" theory.

I am picturing a low and slow oven curing process before the enclosure is closed in, and even before insulating blanket goes on.

James

[maver]

David, that really looks great - very professional, the slate/brick design fits together very nicely.

David how high is your oven opening relative to dome height?

James - does cladding provide stability for the dome joints? Shouldn't the similar thermal properties of the refractory mortar and firebrick align in a well constructed dome as David's appears to be (with very tight joints)? Thes refractory materials shrink with heat, right?