#11  
Old 07-27-2010, 03:56 PM
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Default Re: Why slather mortar on the outside of the dome

Quote:
This raises the issue of cladding vs. vermiculite for insulation.
In what way? They are entirely different things. You MUST insulate your oven either with vermiculite concrete, or a refractory blanket, or both. If you don't your oven won't get up to heat, and won't stay up to heat. Cladding the dome with mortar, on the other hand, is simply icing on the cake. Do it, or not, it doesn't really matter in my book, but don't confuse it with the mandatory insulation.
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  #12  
Old 07-28-2010, 03:00 AM
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Default Re: Why slather mortar on the outside of the dome

If you clad it with an insulating refractory that will not contribute greatly to thermal mass because it's comparatively a low density and correspondingly weaker as a bonding layer. Better to use a denser refractory material that will give you both strength and mass. You need to decide if it is insulation you want or more thermal mass.
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  #13  
Old 07-28-2010, 05:53 AM
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Default Re: Why slather mortar on the outside of the dome

Thanks for the quick response, which helps to clarify my confusion. My question came from the following link: Pizza Oven Construction, where the builder was criticized by Alan Scott for his cladding/insulation. I'm not sure what the problem was, as the oven bricks were coated with refractory, then an aluminum foil sheet and then Vemiculite, as most people have discussed. In my planned build, I will only have about 4 inches once the firebricks are constructed. Hence my problem;refractory or vermiculite cement, and I'm thinking it needs to be the latter, yes?
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  #14  
Old 07-28-2010, 06:19 AM
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Default Re: Why slather mortar on the outside of the dome

Refractory concrete = MASS (no insulation, some structural rigidity). Vermiculite concrete = INSULATION (no mass, no structural rigidity). Extra thermal mass is not required. Insulation is essential.
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  #15  
Old 07-28-2010, 07:37 AM
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Default Re: Why slather mortar on the outside of the dome

I really do not like that base design in the link above.
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  #16  
Old 07-29-2010, 09:51 AM
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Default Re: Why slather mortar on the outside of the dome

The whole thing "hanging" on a few pieces of rebar made me nervous when I was deciding what type to build. Better to overbuild than to underbuild when you have to support that much weight.
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  #17  
Old 07-29-2010, 10:02 AM
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Default Re: Why slather mortar on the outside of the dome

"The whole thing "hanging" on a few pieces of rebar made me nervous"

That is part of the "Alan Scott" design. People should be aware that the Alan Scott type ovens have a very different design and insulation placement than the "Forno Bravo" type ovens usually seen on this site.
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