Wood Fired Oven Questions

Tscarborough

Anything that adds mass is not good. Pea gravel adds mass. Vermiculite is available at garden centers, but perlite is cheaper and available at masonry supply houses. We sell 4 CuFt of perlite retail for $10.35 as an example.

My theory would be that back in the day the ovens were used pretty much every day, so using a dense insulation was not so much of a problem, and was somewhat of an advantage, actually.

Some build on the floor some have the floor float. Since by my calculations the required compressive PSI for a typical oven is less than ten PSI and an 8 to 1 perlite/cement mix is over 50 PSI it doesn't really matter. I built mine on top so I could let the floor run (somewhat) wild and save a few cuts. On a round oven, it would save a lot of cuts to place the dome on the floor.

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joasis

Ok...so you mix perlite 8 parts to 1 of masons mix? Or a refractory cement? Ad no sand, or anything else? And this is placed on the actual base of the oven, and then the firebrick goes on top?

If you were building a brick containment, or outer shell, would you leave it empty, of fill it with rock wool, or plaster it with perlite as well?

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Tscarborough

Perlite and portland cement, although masonry cement should still be fine. No sand (adds mass). Previous to this oven, I had never mixed anything over 1 portland, 2 perlite, 3 aggregate to make lightweight concrete. I made samples from 6/1 to 12/1 perlite/portland, and 8/1 was the most workable. It still is odd to work with though.

I tried various ways to mix it, but the best was to slurry the portland in the mixer, then add the perlite. Add just enough water so that it is damp. I did not mix it long, maybe 3 minutes, then placed it. Mixing the portland and perlite dry did not work at all, don't bother.

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Tscarborough

I am building a shed roof house around mine with wood studs and stucco to match the house (I was given enough standing seam roof to top it) filled with loose perlite. At the minimum, I will have 4" of perlite, but it will average more than 6". I considered several other options and leaned toward making it a barrel shaped structure, but I want to block out my neighbor as much as possible.

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dakzaag

An old mason taught me to use the vermiculite as sand and mix a normal batch. He always put that mix behind the fire brick in a fireplace and above the corbel to form the smoke shelf. First time I did it, I thought it was crazy, but after using it a few times I began to see the insulating value. It won't burn, it is cheap and easy to use. Doesn't get as hard as concrete but if that is a concern, just mix it with more mortar.

Now as far as mixing, I do it totally different. Make a batch of mud like normal but use the vermiculite as sand. It takes at least 15 minutes of mixing before the verm takes up the water. You have to just give it time, but it will eventually take up about the normal amount of water, maybe a little less.

When you grab a trowel full, it really feels weird, like super lite mud or something. I don't lay any brick with it, but it makes a great insulating fill. Takes forever to set up, so mix it on Friday and come back Monday ready to continue.

I bought some stuff by a different name, but it is the same idea as vermiculite. They call it pourable insulation. I had a bag left over last fall, but the dog got into it and spread half way to the moon and back. 4-5 bucks a bag and it is a big bag, not sure if it is 4 cu. ft.?

I will try to pull the old invoice and get the name of the product I used last. I know where it came from, but can't remember the name of the product.

You're not going to find this recipe in any text book, this is an old witches brew that a lot of guys will deny any association with. Probably why it stuck with me.

I used Zonolite, just came back to me. Glad to see the Alzheimer's is fading away again.

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The maintenance schedule for brick
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Tscarborough

Zonolite/Perlite/Vermiculite are all the same mineral in different forms. They expand like popcorn under a high heat process and are then volumetrically stable at high temps.

Vermiculite is a little different than perlite in that the grain size is larger and it is more resistant to abrading while mixing. 6 one way, half a dozen the other so far as insulation.

Most vermiculite or perlite available to us is siliconized since it is usually used for loose fill insulation, so it does not want to absorb water.

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6stringmason

A book I bought is a great read if youre interested in this joasis. It was called The Bread Builders. Great for some plans on domed masonry ovens and it goes very in depth into bread making and cooking recipes and techniques using a masonry oven.

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920-680-3195
Visit our website @
http://www.concretecountertopsdesign.com/

Tscarborough

I have heard that the plans in that book are drawn incorrectly, though. Apparently, they show a slab suspended by rebar with the insulation under the hearth slab. Other than that, I have heard nothing but good about that book.

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jomama

I wish I would have researched this more before I actually built the Buckley oven a few years ago, lots of good info in here.

I found out the hard way that 4" of thermal mass is ideal over the dome especially. Luckily, the HO tested the oven before we got too far, merely needed to pull off some castable.

Mixing your own perlite/portland costs a fraction of what you can buy it for. To mix, we used 2 big plastic totes to shake the stuff up. Compared to mixing standard mortar, this stuff takes ALOT more water. Call me strange, but I actually found the stuff fun to work with as it's so much lighter than the mortar we're acustomed to.

If you're using the 4x8 flues, have someone around with tiny hands/arms to smear the joints for you. I almost got stuck.

A couple of observations of the stoves:

- If you get the oven to 700, you can cook a fresh pizza in ~ 3 mins.
- If you have a good plug made, the inside temp can easily be 300 12 hrs. later perfect for cooking bread.
- I never got the chance ot try the pizza, but the bread was amazing. The odor of it cooking was even better.

6stringmason

Thats true. You have to double check the plans, but most folks on here should be able to figure out that it wouldnt be a good idea lol. It is a great book with alot of info though.

Im planning on doing my masonry oven this early summer up north on some land we have. I'll make sure to take pictures as I go. This is been something I've been wanting to do for awhile now.

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Kamps Masonry & Concrete Countertop Design Green Bay, WI
920-680-3195
Visit our website @
http://www.concretecountertopsdesign.com/