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  #51  
Old 12-16-2009, 07:07 PM
Serf
 
Join Date: Oct 2009
Location: Charlotte, NC
Posts: 22
Default Re: Insulation Efficiency

I am starting to gather materials for my build. My supplier has some 4" wool blanket that is good to 1200 degrees that he will let go for $2/ft^2. My only concern is that this is getting a little too close for comfort in regards to heat. I am just not sure if this is the max temp rating or the working temp rating. With the "mother of all fires" going, how hot would you anticipate the outter portion of the dome will get ( I should mention that I will be casting a dome 3" thick)? I guess a return call is in order! I didn't want to pass it up for that price.

He is also trying to push me on a vermic/portland refractory premix that they sell relativly cheap:

1900 deg-F Insulating Castable (over dome) 30lb/ft^3, so 1 bag covers 1 2/3 cf -50# bag @ $9.00 ea ( I estimate I will need 4 bags to get around 2.5" thick)

Your thoughts??
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  #52  
Old 12-17-2009, 07:13 AM
philiph4@ameritech.net's Avatar
Peasant
 
Join Date: Aug 2009
Location: Farmington Hills, MI
Posts: 26
Default Re: Insulation Efficiency

I haven't posted since I finished my oven so I wanted to give you an update. I ended up using 2 inches of 8# Kaowool covered by 3 inches of vercrete then a stucco finish. Although I don't have a thermometer I can get the dome to go clear in about an hour so it has to be at least 700 degrees F. When I touch the outside of the oven I can't detect any heat. We had our first snow (just a dusting), however, and after about an hour at full heat all the snow melted so it must be getting a little warmer on the exterior. I am having a blast with this oven; pizza galore, lots of fresh baked bread and I even made the Thanksgiving bird. We've had some great parties and my friends love it too. The only problem is keeping my weight down. Oh well, you only live once!

Happy Holidays!

Phil
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  #53  
Old 12-17-2009, 05:47 PM
Apprentice
 
Join Date: May 2009
Location: Austin, Texas
Posts: 102
Default Re: Insulation Efficiency

I laugh along with philiph4 because with my oven just a few months old I find every excuse to fire it up. I bought 2 cords of pecan firewood (1 to use, 1 to age) and I try and fire it up every Friday night. With teens in the house pizza is always a slam dunk, what ever will I do when they go to college? Well that's still 20 months away...
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  #54  
Old 12-21-2009, 12:41 PM
backinoz's Avatar
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Join Date: Oct 2009
Location: Tannum Sands
Posts: 35
Default Re: Insulation Efficiency

Snow is an insulator but I wouldn't suggest it for this application.http://www.fornobravo.com/forum/imag...lies/smile.gif
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  #55  
Old 12-21-2009, 08:21 PM
Journeyman
 
Join Date: Jun 2008
Location: Melbourne Australia
Posts: 399
Default Re: Insulation Efficiency

Quote:
Originally Posted by jbriggs View Post
I am starting to gather materials for my build. My supplier has some 4" wool blanket that is good to 1200 degrees that he will let go for $2/ft^2. My only concern is that this is getting a little too close for comfort in regards to heat. I am just not sure if this is the max temp rating or the working temp rating. With the "mother of all fires" going, how hot would you anticipate the outter portion of the dome will get ( I should mention that I will be casting a dome 3" thick)? I guess a return call is in order! I didn't want to pass it up for that price.

He is also trying to push me on a vermic/portland refractory premix that they sell relativly cheap:

1900 deg-F Insulating Castable (over dome) 30lb/ft^3, so 1 bag covers 1 2/3 cf -50# bag @ $9.00 ea ( I estimate I will need 4 bags to get around 2.5" thick)

Your thoughts??
You will most likely find, if its ceramic fibre blanket it is rated at 1260C not F, so you are safe. You can hold a blow torch on one side of 4" and not feel the heat through it. Melting point is 1700c.
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  #56  
Old 12-23-2009, 09:16 PM
Laborer
 
Join Date: Dec 2009
Location: Christchurch, New Zealand
Posts: 78
Default Re: Insulation Efficiency

Hello
Is it possible to use only perlite portland mix only as insulation and what thickness would you recommend I've been thinking of 100mm (4") in the base and 200mm (8") on the dome?

What is the usual price of the insulating blanket in peoples areas?

Has anyone tried Clay slip and saw dust which I have read of in a few books now?

Any one done clay slip instead of portland cement?

Regards
Bart

Last edited by wemme; 12-23-2009 at 09:23 PM.
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  #57  
Old 12-23-2009, 10:44 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,699
Default Re: Insulation Efficiency

Anything that will bind the vermiculite will work, maybe even flour, but adding mass with either clay or cement reduces the efficiency of the insulation. Use as little binder that you can to retain plenty of air spaces for max insulation efficiency.
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  #58  
Old 12-26-2009, 09:48 PM
Laborer
 
Join Date: Dec 2009
Location: Christchurch, New Zealand
Posts: 78
Default Re: Insulation Efficiency

Does anyone know how the older Clay / Cob Insulations with sawdust or straw compare to perlite and vermiculite concrete?

It is looking like my insulation cost will be about 150% of my Thermal mass cast layer!
I can get all the other cob technology items for free or at least cheap.

has anyone tried Styrofoam bean that are used in bean bags combined with clay/concrete for insulation? even thought the beads break down at low temperature they will leave an air pocket in the clay.
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  #59  
Old 12-26-2009, 10:13 PM
Journeyman
 
Join Date: Jun 2008
Location: Melbourne Australia
Posts: 399
Default Re: Insulation Efficiency

That would be unusual but most likely OK. The old insulation bricks used to be made with clay and sawdust, when they got fired at 1200c the sawdust burnt out giving a lightweight brick. Same deal actually.
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  #60  
Old 12-27-2009, 03:21 AM
Il Pizzaiolo
 
Join Date: Mar 2009
Location: USA
Posts: 1,436
Default Re: Insulation Efficiency

wemme,,
might work, I only would be worried about any leftover stink or chemical from the stryofoam,,, but a high heat fire would probably burn of all the smell and chemicals, I hope.. Maybe like Johnny said you could use sawdust, a lot more organic.. you would need it to be a little bigger than regular sawdust, more like chips from a chainsaw i think.
keep us posted
cheers
mark
P.S. remember necessity is the mother of invention
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