#11  
Old 12-25-2008, 04:22 PM
Serf
 
Join Date: Sep 2008
Location: Haleiwa, Hawaii
Posts: 17
Default Re: Building an oven in Hawaii

I am so perplexed. I am about to build the oven. I have one layer of used brick, which I was told is firebrick but I am not sure. I laid the brick flat so they are 3 inches high. I dry set them and encased them in a perimeter of cement. I have extra Kaowool and also refractory cement Mizzou. Can I use this in combination to insulate the oven floor? I don't want to spend more money but I may have to. Thanks for your thoughts on this. Paul
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  #12  
Old 12-25-2008, 05:27 PM
Il Pizzaiolo
 
Join Date: Jan 2007
Location: Tampa, FL
Posts: 1,446
Default Re: Building an oven in Hawaii

First of all, your insulation needs to be DIRECTLY under your hearth firebricks. It sounds like you have set your bricks and are looking to insulate under the hearth slab and bricks, if this is the case, you need to rethink your build. You will use an incredible amount of wood heating both the brick hearth and support slab...you may not be able to reach pizza temps at all. A 3" thick hearth is MORE than enough for retained heat cooking and should work fine if insulated directly under the brick.

I don't see how you can use the kaowool blanket for hearth insulation, as dmun mentions, compression will defeat the insulating value...there is a reason it is a spongy blanket - the air within the blanket gives it the insulation value. Save all of your kaowool blanket for dome insulation, more is aways better.

With all of the horticulture in Hawaii, there has to be someone who sells perlite or vermiculite - have you tried garden centers? Or maybe a local grower? Any shipping supply companies? Both are used as a lightweight packing material, especially for shipment of liquids in glass bottles. If all else fails, you may have to bite the bullet and have Ceramic fiberboard shipped from the mainland.
Seriously, don't rush into completing your oven without acquiring a suitable insulation and remember our mantra - INSULATE, INSULATE, INSULATE - you can never have too much.

RT
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  #13  
Old 12-25-2008, 05:36 PM
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Join Date: Sep 2008
Location: Haleiwa, Hawaii
Posts: 17
Default Re: Building an oven in Hawaii

I appreciate that and I agree. The fire brick that I mentioned that I laid is not the fire brick I will use for the oven. It is part of the hearth slab nicely placed and tight. I have been looking everywhere for vermiculite and the only one I found here is white pellets. Does refractory concrete provide insulation for the hearth oven floor if I incorporate 2 inches into the hearth slab? Thank you Paul
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  #14  
Old 12-25-2008, 06:13 PM
Il Pizzaiolo
 
Join Date: Jan 2007
Location: Tampa, FL
Posts: 1,446
Default Re: Building an oven in Hawaii

Refractory cement only means that it has a high alumina content allowing it to withstand the high temps and withstand the "cycling" of heatup, cool down, heatup.

If it specifically says insulating, yes it would be suitable. This type of cement is usually "insulating castable refractory", meaning it has insulating properties added to castable refractory cement. again, castable products are always specifically labeled as such.
The bottom line - refractory cement merely mimmicks the properties of firebrick, unless it specifically says insulating in the name, it has no more insulation value than your firebricks.

I don't know if this helps, you can order course vemiculite from Uline.com in 4 cubic ft bags. I typed in a quantity of 4 bags ($20 each= $80) and your city (Haleiwa); the cheapest shipping method would be Parcel Poast (and take up to 15 days - shipping from CA) at $87, for a total cost of $167.
You may want to CALL Forno Bravo and inquire about the FB ceramic fiber board, they may be able to ship for the same/less total cost, and the board is the best insulator to use. It will also ship from CA.

RT
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  #15  
Old 12-25-2008, 06:56 PM
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Join Date: Sep 2008
Location: Haleiwa, Hawaii
Posts: 17
Default Re: Building an oven in Hawaii

thank you RT. Below is the link to the data sheet. Please let me know if you think it is insulating. I do understand what you are saying and appreciate it.

http://www.hwr.com/products/datashee...U_CASTABLE.pdf
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  #16  
Old 12-25-2008, 07:32 PM
Il Pizzaiolo
 
Join Date: Jan 2007
Location: Tampa, FL
Posts: 1,446
Default Re: Building an oven in Hawaii

Paul, I'm not an expert on castables but I will give you my take from researching products on Harbison Walkers site (hwr.com).

General castables (with little or no insulation value) tend to have a higher content of alumina than silica as well as lime. These castables have a 55% - 90% alumina content and a lime content of around 2%-6%. The Mizzou Castable that you have appears to be a medium duty standard castable that is not intended to have any insulating value.
Insulating castables have a silica content greater than the alumina content - about the same 55% +; with a lime content of 6% - 12%.

The Harbison Walker site lists your Mizzou Castable as a standard castable, not in the insulating category. You might want to check out the site, very informative with all of the products listed by category and trade names with data sheets - for dozens of refractory products.

RT
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  #17  
Old 12-25-2008, 08:41 PM
Serf
 
Join Date: Sep 2008
Location: Haleiwa, Hawaii
Posts: 17
Default Re: Building an oven in Hawaii

RT thank you for your abundant and thoughtful advice and time. Aloha Paul
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  #18  
Old 12-25-2008, 10:11 PM
Il Pizzaiolo
 
Join Date: Jan 2007
Location: Tampa, FL
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Default Re: Building an oven in Hawaii

You are welcome...thats why we are all here - to help each other build the best oven possible within our means. Good luck with the rest of your build.

RT
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  #19  
Old 12-29-2008, 06:16 PM
Serf
 
Join Date: Sep 2008
Location: Haleiwa, Hawaii
Posts: 17
Default Re: Building an oven in Hawaii

RT: I ordered the ceramic board from FB and it shipped today. Do I just lay the brick, oven floor, on the board? Thanks Paul
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  #20  
Old 12-29-2008, 06:52 PM
Il Pizzaiolo
 
Join Date: Jan 2007
Location: Tampa, FL
Posts: 1,446
Default Re: Building an oven in Hawaii

That should do it. The board provides the flattest surface possible for the hearth bricks, which makes laying the bricks a snap. With any luck you have bricks that are uniform in thickness and high spots will be minimal. The herringbone pattern seems to be the best choice for you brick pattern - if you should have a high edge on any of the bricks. The diagonal herringbone keeps your peel from catching squarely on a high edge, reducing the possibility of a big chip in a brick.
If you do have any high spots after you set the bricks, you have a couple of choices to level them - a little dry fireclay as a bed on top of the board (under the bricks) OR the belt sander method which many of us have used with great success. Take a 40 or 60 grit belt and sand down the high spots ( I then used a medium to smooth even further). No need to sand the entire hearth, just the high spots. Hope this helps.

How about posting some pics of your progress? The wild bunch on this forum LOVE photos.

RT
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