#1  
Old 12-02-2007, 09:51 PM
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Location: Beijing, China
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Unhappy New Pizza Oven in Beijing, China - Help!

Hi all,
With the help of a local contractor, I've just finished building a dome-shaped, pizza oven in my pub/restaurant, and have a couple of questions that I'd be very grateful if anyone could help me out with! I wish I'd discovered this website before we started, because being in Beijing, I've kind of been flying blind on this one! We gave it a good shot, but unfortunately, I reckon that a few crucial steps may have been missed...

1. I've been testing the oven this weekend, and I'm actually getting good temperatures with the oven. It gets up to 400F pretty quickly, but I find I have to "split" the fire to the two sides of the oven otherwise the temperature stays too low. (The first time I did this, the temperature rose to +-600F without a massive fire). Is this normal to have to have two small fires, though?

2. The pizza cooks in a minute and a half to two minutes, but the bottom of the pizza doesnt seem to be cooked enough. (It stays white and doesn't get brown enough). I'm using firebricks for the floor of the oven - should I be using some other type of material? Does anyone have any recommendations as to what kind of material would be better? Also, the floor seems cooler than the rest of the oven. Could this be caused because I don't have enough insulation under the floor? (Actually, I have three layers of firebricks forming floor. Bad idea? Too much mass?) As far as I know, there isn't a layer of sand or anything under the firebrick layered floor.

3. After cooking for a while the outside of the dome is getting pretty hot (and I'm getting cracks). Should I add more insulation around the dome? (I'm thinking about removing the top layer of cement from the dome and adding foil and / or fireglass insulation before recovering with cement). Any suggestions?

4. I seem to have to use quite a lot of wood to keep the temperature at optimal cooking temperature. My pub is open all day, so having to burn this amount of wood to serve pizza is going to prove very costly. What amounts do others find they have to burn to keep a cooking temperature? (Any estimates?) I don't need the oven to bake bread - just pizza.

5. If I've missed too many things building this one, does anyone have any suggestions as to how to rescue this project? (I'd rather not have to do a complete tear down).

I've attached a couple of photos of the oven during the construction stage. (To make the dome shape, we actually welded a metal dome-shaped frame. The idea was to cut it away later on. Has anyone else used this approach?)

Thanks for all the great posts on this site! Any comments and/or suggestions would be much appreciated!

Cheers,
Mike
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New Pizza Oven in Beijing, China - Help!-oven1.jpg   New Pizza Oven in Beijing, China - Help!-oven2.jpg  
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  #2  
Old 12-03-2007, 04:43 AM
Ken524's Avatar
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Default Re: New Pizza Oven in Beijing, China - Help!

Hi Mike,

Welcome to the forum!

It looks like your primary problem is the floor; too much mass and no insulation underneath. Your floor is acting like a heat sink and sucking up all your heat (and not getting hot).

The ovens that most of us are building (designed for pizza) have one layer of firebrick on the floor (about 2.5" thick) and a 2" - 4" thick layer of insulation under that.

Are your floor bricks mortared in place? If they aren't mortared, pull the 3 layers of brick out, pour in 4" or 5" of vermiculite concrete (http://www.fornobravo.com/pompeii_oven/hearth_slab.html), then replace the top layer of brick. I'm guessing that will solve 90% of your problems.

If you don't have any insulation on the outside of the dome, you may be OK by simply adding some. Sounds like your dome has a lot of mass, but that's not necessarily a bad thing as long as you can retain all the heat energy are putting in to it.

For the dome, you have several choices; the best in your situation is probably refractory blankets like this:

http://www.fornobravo.com/store/Insulfrax-p-16152.html
or this:
Product Category - Blankets

2"-3" inches of blanket will keep your heat in.

Again, I think your primary concern is the floor.

Good luck!! and keep us up-to-date on your progress.
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  #3  
Old 12-03-2007, 07:45 AM
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Default Re: New Pizza Oven in Beijing, China - Help!

Insulate! Insulate! Insulate!

Depending on your cost of firewood it might be cheaper to rebuild than to keep firing this thing to heat up the surrounding masonry and air, rather than your cooking area.

As Ken said, you have WAY too much mass under your oven, with three levels of firebrick, and whatever it's sitting on.
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Old 12-03-2007, 07:01 PM
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Location: Beijing, China
Posts: 2
Default Re: New Pizza Oven in Beijing, China - Help!

Thank you very much for the excellent replies. Your advice is much appreciated!

What you have both said makes a lot of sense. Running the oven as it is at the moment is going to prove way to costly - I need the oven going for around eight hours a day, and the amounts of firewood I'm going through right now just doesn't make it affordable.

I guess that this Christmas I'll be doing a tear-down and rebuild job!

Here's what I'm planning on doing:
1. I'll remove the layers of firebricks on the floor and lay an insulating floor. I'm not sure where I can find vermiculite concrete here in China, but it should be available.
2. I'll then rebuild the dome and cover with refractory blankets. On top of that I'll recover with cement.

I'll post some photos and let you know how it goes.
Thanks for all the advice!
Cheers,
Mike
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Old 12-04-2007, 12:26 AM
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Join Date: Oct 2007
Location: Sacramento, CA
Posts: 575
Default Re: New Pizza Oven in Beijing, China - Help!

Welcome Mike,
I don't think Ken was suggesting a complete rebuild. Sounded slightly simpler to me. I think he meant that if you could remove the floor, and then replace the firebricks underneath it with insulation, like vermiculite mixed with cement, then replace the floor, that would solve most of your problem. And I agree. Expecially when you mentioned the bottom of the pizzas. The floor is too massive for the fire to heat up. Maybe your contracter could even saw out the floor with a diamond blade in his skill saw. With this method he could only get about 2 1/2 iches from the dome wall, but, even with that, it would be a tremendous improvement - and still leave the dome itself intact. Then you could insulate the top and sides with some kind of insulating blanket, woven ceramic insulation stuff, or even fiberglass R-19 if that's all you could find there, and you would be back in business. I'm thinking that the dome could remain if you could insulate the floor and then the outside. But expecially the floor.

Hope this helps, and keep us informed

dusty

Last edited by dusty; 12-04-2007 at 12:35 AM.
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Old 12-04-2007, 05:19 AM
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Default Re: New Pizza Oven in Beijing, China - Help!

Quote:
I'm not sure where I can find vermiculite concrete here in China, but it should be available.
Mike,

Vermiculite concrete is something you make yourself (it's not something you'll "find"). It's a mixture of vermiculite or perlite (garden shops, horticultural suppliers) and portland cement. Other options are Calcium Silicate board and Kaowool board. There should be a refractory supplier in Beijing. They will understand what you are looking for.

Before you do *anything*, you need to do more research. This forum and the Forno Bravo website have everything you need. Go to the Pompeii oven plans page (Pompeii Plans) and read the plans from start to finish a few times so you get a good understanding of how all the components of the oven work. We can help you find answers to all the questions you come up with.

We're here to help! You don't want to fix this thing twice
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42" Pompeii


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Old 12-04-2007, 07:04 AM
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Default Re: New Pizza Oven in Beijing, China - Help!

An angle grinder with a diamond will cut around your floor, as well, and get closer to the edge than a skill saw.

If you decide to replace the floor/insulation you could also consider cutting/breaking a couple of the first course bricks away, inserting timbers, and jacking up the dome from the sides, to rebuild the floor. Remember: the large FB prefab oven can be lifted by four people. It has handles. You should be able to lift yours as well if you can get it loose from the floor.
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Old 12-04-2007, 09:28 AM
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Default Re: New Pizza Oven in Beijing, China - Help!

HM,

Not a lot to add to the excellent advice already provided. However, it appears that your dome bricks are touching the walls. What are the walls made from? I'd be a bit concerned about undue heat transfer into the walls, particularly if they are combustible in any way. You'll have to cut them back a bit to make room for insulation batts (I'd recommend two inches), plus as much vermiculite/Portland mixture as you can fit between the dome and whatever is behind the walls.

Jim
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Old 12-04-2007, 09:51 AM
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Default Re: New Pizza Oven in Beijing, China - Help!

I can jump in here.

If it is possible, I would try to find insulating blocks, rather than vermiculite. They are a great deal more efficient, and will be much easier to add a 1 or 2" layer of block, rather than mixing and pouring vermiculite.

I know that Alumina Silicate insulation is made in China, though I don't know where you would buy in retail.

I think it is very cool that you have built your oven -- and I hope it all goes well from here on.

James
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Old 12-04-2007, 08:32 PM
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Default Re: New Pizza Oven in Beijing, China - Help!

I'm off ot Shenzhen china next week. If I could only find wood fired pizza there......

Christo
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