#21  
Old 09-20-2007, 10:22 PM
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Default Re: Questions, Questions, Questions

With Dan's oven, it's easy - insulate, then cure. With a pompeii, some people are nervous about cracks and would like to seal them prior to insulating (after curing), although by curing without insulation you may increase the risk of cracks. I think if you have a solid insulation like a blanket or vemiculcrete it's probably best to insulate first to reduce thermal differentials that could increase the likelihood of cracks.
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  #22  
Old 09-21-2007, 05:38 AM
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Default Re: Questions, Questions, Questions

I am doing a Casa 90 in gabled house. I have already mortared the seam and lower outside of the oven. I plan to insulate with blanket and loose vermiculite (4"). What I'm hearing is that I should cure after insulating. Any other thoughts? Thanks again.

Fred
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  #23  
Old 09-21-2007, 06:24 AM
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Default Re: Questions, Questions, Questions

Hi Fred.

There's no reason to cure before insulating. Part of the curing process is to drive any water out of the insulating layers. Although pre-cast ovens are much more thermal shock tolerant than brick built ones, you still subject your oven to less stress by not firing until you insulate.
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  #24  
Old 09-21-2007, 07:45 AM
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Default Re: Questions, Questions, Questions

Quote:
Originally Posted by Dan94550 View Post
What does this mean?
What I meant was that I thought Dan's re-statement of the situation was correct. This was obviously the wrong term to use as it was confused with a refractory mortar cap.

J W
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Old 09-21-2007, 09:28 AM
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I agree with dmun. I covered the dome with a layer of mud and after it dried I put on the ceramic blanket. Most of my hot fires were done with the insulating blanket on. I did notice something rising from the dome late in the first few hot fires and thought at first that I had a smoke leak. Turned out to be steam working its way out of the bricks and through the blanket. Finally exhaled! The blanket would be damp after the fires as the oven continued to dry out. Finally nothing, not even any real warmth could be detected.
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Old 09-21-2007, 10:00 AM
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Default Re: Questions, Questions, Questions

Just to present another point of view, I cured before insulating. This allowed me to patch the small cracks that appeared. If you insulated first and then cured, I don't know how you would identify and patch the small cracks that inevitably occur...

Drake
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  #27  
Old 09-21-2007, 09:51 PM
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Default Re: Questions, Questions, Questions

I think I was trying to indicate that for the pompeii where cracks are fairly likely, curing first, then patching cracks, then insulating may make sense, but for precast like Dan (as James has also said), insulating then curing should be ok.
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Old 09-22-2007, 06:57 AM
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Default Re: Questions, Questions, Questions

I'm probably in favor of a modified approach. Apply the ceramic blanket and wire it down. Do the oven drying fires to the point that you are satisified.

Number the blanket pieces with a marker or tag, remove and inspect and repair as required. (it's what I ended up doing with my oven)

I really feel having an insulation layer is important to reduce stress/expansion deltas.

Christo
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  #29  
Old 10-23-2007, 09:10 AM
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Quote:
Originally Posted by James View Post
I can jump in here.

With a precast oven (such as the FB Casa or Premio), you use a band of refractory mortar outside the joint, without pointing mortar into the joint. That completely seals the oven and keeps all the heat and air inside the oven chamber.

If you want to add more mass to the oven, you can also coat the rest of the dome with 1/2"-1 1/2" of refractory mortar. That will give you more mass for retained heat baking (such as bread), and will require a slightly longer heat up time.

The reason you seal the outside of the joint is to allow for thermal expansion and contract. Otherwise, the mortar inside the joint would eventually crack and fall in. Our oven producer (and experience) is really clear on this one.

James

I just came across this and with all due respect it does not make sense to me, then again I have no experience with the bagged refractory mortar. If James or someone could explain further I would appreciate it. The true refractory mortars really interests me and I'm trying to understand them better.

Here is my issue, if its not advisable to put the mortar in the joints because "the joint would eventually crack and fall in" , how is putting a band of mortar on the outside any different in this regard? Its still going to be subjected to expansion and contraction and since it is on the surface its got 3 plains to deal with instead of 2 (2 dome sections moving and the dome itself expanding and contracting) I just don't get it

Having the band, weither it is thick or thin its still resting on a cold joint between two surfaces we know are going to move, my logic tells me its gonna crack right where the joint is. Is this stuff that plastic that it expands and contracts? and if so why would that ability to do so not work in the joints?

If the manufacture recommends this there is clearly logic I'm missing, I would just like to understand it.
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