Starting new 36" build

[deejayoh]

Re: Starting new 36" build

I have a question about insulation between the hearth layer and the cooking floor:

I purchased 2" of FB Board insulation to install under my oven. The spec sheet for the board says that:

"One 2" thick layer of FB Board panel reduces the 800?F cooking floor of a pizza oven to roughly 170?F at equilibrium"

I have seen recommendations for 2 layers (4") of the FB board on the board. That seems like total overkill to me - as the goal of the floor insulation should be to reduce the heat transfer to the point where it is equivalent to roughly the temperature of the hearth - about another 100-130 degrees

Beyond that point, you really aren't losing any heat so you are past the point of diminishing marginal returns from insulation

I am trying to figure out if there is a cheaper material I can use at 1" thickness to accomplish that last bit of temperature reduction. Something I can source locally that is more in the $5/sq foot price range than the $12 per sq foot that the FB board costs.

Any suggestions? Would an inch of perlite do the trick?

[GianniFocaccia]

Re: Starting new 36" build

1" of ceramic board is equal to 2" of vermicrete or perlcrete. I put in 3 1/2" of vermicrete (easy to mix and install) under 2" of board, which is becoming common. 1" of perlcrete isn't going to do much for you.

[deejayoh]

Re: Starting new 36" build

1" of ceramic board is equal to 2" of vermicrete or perlcrete. I put in 3 1/2" of vermicrete (easy to mix and install) under 2" of board, which is becoming common. 1" of perlcrete isn't going to do much for you.

Thanks Gianni
So it takes 3 1/2 inches of vermicrete to manage 170 degree temperature? Seems like a pretty inefficient insulator.

Due to height limitations I am looking for something no more than 1" thick

I saw this at our local pottery supply. This board looks like it might do the trick. Any thoughts?

[GianniFocaccia]

Re: Starting new 36" build

Can't tell, DJO. Maybe you can email them and ask for the board's R-Value and MSDS, which will tell you the board's composition. Since you'd be using it as backup instead of hot-face insulation, I'd be tempted to use it as long as it's compressive strength is acceptable.

[deejayoh]

Re: Starting new 36" build

Thanks gianni. BTW, I have learned a lot from reading about your build, as I get ready to start cutting bricks on mine.

[GianniFocaccia]

Re: Starting new 36" build

Cool, DJO. If you have questions, just holler.

The board Seattle Pottery Supply is selling for $10 is Insblock 19, the same mineral wool board alot of us (including me) used in our ovens. I paid $75 for a box of eight 2"x36"x12" boards, but only because the box had been 'torn open by a forklift blade' and scuffed one of the boards.

Although I can't tell you how the board performs, others here can. Since 16 1" boards will cost you $160, it's still a pretty good price. If I had it to do over again, I would add one more layer for a total of 3" on top of my vermicrete.

Let me know if you'd like me to email the MSDS I got from Seattle Pottery Supply.
Gianni

[deejayoh]

Re: Starting new 36" build

Finally got the hearth poured, so I am finished with this phase of work.

Since the back half of the hearth is "on grade", I used a concrete additive called Xypex Admix C-1000 to waterproof the concrete and keep moisture out of my oven. It is supposed to create a crystalline structure inside the concrete that blocks the capillary action. It's typically used in swimming pools, sewage plants, and other high water situations. Hoping it will do the trick for me.

Picking up my bricks on Saturday morning!


Gianni -
thanks for the info on the board. I am going to get 1 inch to supplement the 2" of FB board I already have. That will put me at 46.5" opening height, which I think is perfect.

[GianniFocaccia]

Re: Starting new 36" build

I am going to get 1 inch to supplement the 2" of FB board I already have

Sweet. You're gonna love the heat retention and slower oven coast.

[deejayoh]

Re: Starting new 36" build

Lots of progress today! Picked up the final layer of floor insulation last Thursday.

Today I laid the floor insulation, cut the bricks for the floor, and got about 1 and 1/4 courses of "sailors" cut

I am planning to lay 3 vertical sailor courses, and then start angling the dome. I am going to build an elliptical dome like Dr Sewards, so will be using an off-center IT that rotates on plywood lazy susan to get the angles all correct and have a flat plug.

Here are some updated pix + a shot of parts for my super-cheap IT, inspired by Cheesteak!

[GianniFocaccia]

Re: Starting new 36" build

Great start, DJO. Dr Seward's build has to be one of the tops for build quality and design.
Keep the pics coming.
John

[Amac]

Re: Starting new 36" build

You're a neat worker djo - this'll be a good one. Keep it going. The building process is a lot more fun than I expected - enjoy it - it's magic!
Aidan

[deejayoh]

Re: Starting new 36" build

I have been working on the design for the vent/landing - and I just realized that I may have an issue. I was planning on a 9" landing - basically the length of a single fire brick. But I bought (and am planning to use) an 8" duravent anchorplate - which I now see is going to be tough to fit on top of a 9" long vent arch as it has 12 x 12 footprint

Kind of crazy because the FB plans call for a 8-9" vent, and the use of an 8" flue - so how is this all sposta fit? Am I missing something?

Can you have a narrower, longer slot in top of the vent (say something like 5x10= 50" area) that feeds into an 8" round flue (which is also about 50" area)? Will that work?

What have others done/planned?

[david s]

Re: Starting new 36" build

Yes you can. IMO it is worth the effort to make the entry as shallow as you can, which makes the oven easier to work.

[deejayoh]

Re: Starting new 36" build

Well, good progress to report this weekend. Both days were rainy, blustery, and cold - and as I probably don't need to tell most of you, working with that tile saw leads to some pretty cold hands! But I persevered between trips inside to warm myself - and ended up getting the bricks all cut for the first three courses and the arch.

I'm going to try to follow John's (Gianni) approach on the arch - where you cut the back to conform to the dome - so am planning to leave those un-mortared until I get the rings going. Actually, for now the whole thing is unmortared - because I can't seem to find cement and lime in bags less than 100lbs, and also can't find anything but sandbox sand. Anyone have any guidance on where I might find 50lb bags, and fine sand?

Oh, and I am producing a whole mess-o-fireclay. I didn't really believe it when people said you really don't need to buy fire clay - and now I have an 80lb bag of it and am finding it in my water tray by the bucket load! Newbies take note, learn from my mistake!

Other than that, I am feeling pretty good about the progress. Take a look at my arch geometry and tell me what you think. The "corner" pieces are not final in the picture I posted - but I have finished those too. Ended up using 3 bricks turned on their side to get just the right height/angle. It involved some pretty intricate cutting. I'll try to post a shot of that later.

Pictures are attached. I finally figured out the thumbnail thing!

[deejayoh]

Re: Starting new 36" build

Yes you can. IMO it is worth the effort to make the entry as shallow as you can, which makes the oven easier to work.

Thanks for the reassurance. I did some more investigating and it looks like Ken solved this on his "Kentucky dome". I'm planning to work off of his design. I will probably use refractory cement for the final mounting of the anchor plate instead of mortar - but the basic design seems like it should work.

http://www.fornobravo.com/forum/21/m...html#post19105