Several questions from a beginner

[whocanitbenow]

Hi, I've finished building my stand and will pour the insulation slab tomorrow. This site has been exceptionally helpful and I wanted to post a few questions that have been nagging me.

1. Was there any resolution about whether to set the Super Isol directly into the wet structural concrete or wait for the slab to cure?

2. I live in an urban environment and have a small back yard. My stand is 48" x 56". Will I be able to build a reasonable oven on this small a stand (I am looking for something for weekend use, maybe two small pizzas and some other vegetables)?

3. How far in from the sides and back of the slab should the firebricks for the floor be set?

4. I am building a taller style dome. Should I use a styrofoam form or should I try it free hand?

5. The plans on the site mention a "second" insulating blanket under the Oven Insulation section for the Igloo shape. What is this? Is it just the vermiculite concrete layer? Are there two of these?

[Chris]

1. I didn't use Super Isol, but I will on my next oven. After hearing about how it soaks up water like (better than?) a sponge, I'd wait a day or two and then set it on top. Make sure your concrete is nice and level and smooth.

2. My dome is 3" thick, and it worked fine on my first pizza bake. If you build the 36" dome, you'd still have 3" of room for insulation on each side. Look into the insulating blankets.

48" stand - (36" diameter + 3" brick * 2 wall) = 6" / 2 sides = 3"

3. That depends on what you're using for insulation. I used perlite, so I needed to allow 6 inches on each side. Use the highly efficient blankets, and you'll save space (and dust!).

4. I built a 20" tall dome, with a diameter of 42". Using a template, I was able to build about nine courses of brick rings up before using a styrofoam form. At least one person did not use forms at all. Some use forms from the beginning. I liked being able to fill and smooth the joints from the inside as I was working, so I am glad I didn't use the form in the beginning.

5. As I understand it, most people choose one of the following:
a. 6" to 8" of perlite or vermiculite
b. one layer of insulating blanket and 4" of perlite
c. two layers of insulating blanket and ? of perlite

-CC

[maver]

Most of this varies from my oven, and well answered by Chris, so no comments.

Originally Posted by Chris

4. I built a 20" tall dome, with a diameter of 42". Using a template, I was about to build about nine courses of brick rings up before using a styrofoam form. At least one person did not use forms at all. Some use forms from the beginning. I liked being able to fill and smooth the joints from the inside as I was working, so I am glad I didn't use the form in the beginning.

Mine was a low vault pompeii and I was another who built with no forms, just a series of shims for each ring of the arch. It works very well, and allows you to see and control the inner face of the oven during construction. I'd also add that it is fairly quick and efficient. The downside, is that for some of the upper rings it gets to be a challenge, unless you have help. If you have another set of hands, you are in good shape with the shim method.

[whocanitbenow]

Thanks guys. What did you guys use for your high heat mortar? I was considering the Refmix on the Forno Bravo site, but it seems weird to ship all that dust across the U.S. Is there anything else I can find locally that is an equivalent mix? I don't trust myself to get the mix just right on my own (I had enough trouble with regular concrete!)

[dmun]

On the east coast the locally available product is heat-stop. People who have used the both say refrax is better, but I think heat-stop is fine.

Anyplace that sells firebrick will sell some kind of refractory mortar. Look for the dry powder mix, rather than pre-mixed stuff in tubs.

[james]

Hello Who,
It's really nice dust, though. If you strike out finding mortar locally, we're here.
James

[james]

One more thing. Send photos.
James