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-   -   HELP! Can I cure and test oven before enclosing? (http://www.fornobravo.com/forum/f8/help-can-i-cure-test-oven-2690.html)

Nick 10-03-2007 05:00 AM

HELP! Can I cure and test oven before enclosing?
 
My mason has a mind of his own. I gave him the Pompeii oven plans MONTHS ago an have talked to him about what I want (a neopolitan low-dome) but he pretty much works out the design in his own head and does what he wants. So far this has been okay. He really is a talented man. He started the dome this week. He's just about to the point where he'll fill the oven with sand to finish off the dome. (He decided he didn't want to do the extreme neopolitan, so we agreed on a hybrid.) Last night I went out and measured the cooking floor. It's barely 40" and it was supposed to be 42!

In and of itself, this is not an oven-killing thing. But since he has obviously not followed the instructions, I'm concerned he'll do something else that will result in a poorly-functioning oven. He's a very stubborn man.

My question is: Can I cure the oven once the dome is complete and then test it to see how it works? Should I install the insulfrax blanket first? Before curing or just before full firing?

There's always a chance the oven will work perfectly. But if it doesn't, I don't want to have to tear down the outer wall, roof, etc to rebuild it. I can live with just tearing down the oven and starting on the base again. If testing the oven at this stage (assuming a full cure as outlined in the plans) isn't possible, I will tear it apart and start over from the base.

Thanks for your help!

Dominick

asudavew 10-03-2007 07:36 AM

Re: HELP! Can I cure and test oven before enclosing?
 
I think most have concluded that it's best to insulate and do the curing fires.
(less thermal shock)

That can be accomplished with the fiber blanket.

There are other opinions though. Some have cured without insulation at all.

Good Luck!

dmun 10-03-2007 08:09 AM

Re: HELP! Can I cure and test oven before enclosing?
 
Quote:

Originally Posted by Nick (Post 16391)
He's just about to the point where he'll fill the oven with sand to finish off the dome.

Just a point, I think this sentence means that he is using the sand as a form to build the last courses. There are traditions of INSULATING the oven with sand. Just make sure he's using real insulating materials, not cheap sand around your dome.

Kemo 10-03-2007 08:24 AM

Re: HELP! Can I cure and test oven before enclosing?
 
post some pics... :)

DrakeRemoray 10-03-2007 08:56 AM

Re: HELP! Can I cure and test oven before enclosing?
 
For the record, I cured mine before insulating, this helped me identify and fill cracks.

I have read the arguments about insulating before and how that may cause less thermal shock. I don't see how that could be true. If anything it would mean that the oven gets hotter when insulated, therefore more thermal shock...call me a doubter...
Anyway, I would cure it first and patch the inevitable cracks, then insulate and build the enclosure...

Drake

asudavew 10-03-2007 09:24 AM

Re: HELP! Can I cure and test oven before enclosing?
 
Quote:

Originally Posted by DrakeRemoray (Post 16410)
I have read the arguments about insulating before and how that may cause less thermal shock. I don't see how that could be true. If anything it would mean that the oven gets hotter when insulated, therefore more thermal shock...call me a doubter...
Drake

Good point.

I hadn't though about it that way.

If the blanket is on, I guess it would get hotter faster, but wouldn't it cool more slowly? Maybe heat it up with no blanket, then throw one on for cooling
down. ;)

But apparently, either/or has proven to work.

Unofornaio 10-03-2007 09:33 AM

Re: HELP! Can I cure and test oven before enclosing?
 
Got to agree with Drake. Curing the chamber first exposes weaknesses that could potentially damage the insulation layer and provides the opportunity to fix them.
In addition when curing the oven it moves in all directions more radically than it does once cured.

Then again many have cured it after without ill effects.

wlively 10-03-2007 02:29 PM

Re: HELP! Can I cure and test oven before enclosing?
 
May or may not be a big difference with firebricks, but the thermal stress is greater without insulation, no doubt about that. The stress is greater because the temperature gradient across the brick or dome is greater and that gradient is what produces the stress.

Again, while it may or may not make a huge difference, I believe it is better to fire/cure after at least a blanket of insulation. That is what I did. If you have cracks or want to inspect it is no big deal to pull back the blanket. I am still 100% crack free.

To each his own.:)

Nick 10-03-2007 03:19 PM

Re: HELP! Can I cure and test oven before enclosing?
 
Thanks for all the great advice.

The sand was just for the form, not for insulation. We have several bags of vermiculite for that. Plus, I've ordered the insulfrax blanket from Forno Bravo. Not sure when that will arrive!

The mason finished the dome today. It looks great. I will post some photos once I figure out how.

I like the idea of curing the oven with the blanket, but then removing it to check for cracks and make repairs.

According to the plans, I need to wait a week before starting the cure anyway.

Thanks!

DB

Unofornaio 10-03-2007 03:26 PM

Re: HELP! Can I cure and test oven before enclosing?
 
[QUOTE=wlively;16429] The stress is greater because the temperature gradient across the brick or dome is greater and that gradient is what produces the stress.
QUOTE]


Not disputing this theory in any way I just want to understand more. Did you arrive at this with the fact that the insulation is holding the heat in mind? Meaning, since the insulation is, for lack of a better description, distributing..(actually encapsulating may be a better term) the captured heat its causing the dome to heat more evenly? Thus reducing stress.


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