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  #151  
Old 03-08-2013, 02:02 PM
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Location: Los Angeles
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Default Re: 36" Pompeii in DC

Im in the same boat, i want the exposed dome. I plan on doing smooth stucco with fine sand. But with all this talk about moisture and roof over the dome has got me thinking about putting a roof or covering on rainy days(not that we get much)
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  #152  
Old 03-08-2013, 02:10 PM
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Default Re: 36" Pompeii in DC

I don't personally have any experience with an exposed dome, but my thinking was that it seemed awfully vulnerable in a wet climate (got plenty of that) and would be even more worrisome if freeze/thaw cycles were an issue. Moreso given a lack of experience with stucco on my part. That's why I went with the doghouse. If I was in California or Arizona, I'd do a dome in a second!
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  #153  
Old 03-08-2013, 02:31 PM
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Default Re: 36" Pompeii in DC

I've had my oven going on 3 years now, with a stucco finish and have had no issues with moisture from the exposed dome. I live on the coast and during the typhoon season, we are hit hard, the problem is the horizontal rain, sometimes soak the firebricks in my vent getting hearth insulation wet. I solved that problem by sealing the bricks in the vent area with sodium silicate. Rather than enclosing my oven, I would like a covering over my work area and the oven opening, the summers here a brutally hot and sunny, shade would be a blessing.
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  #154  
Old 03-11-2013, 07:52 AM
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Default Re: 36" Pompeii in DC

Well, I did two long, low fires in the oven this weekend. Saturday fired for 5 hours with 2-3 logs at a time. Put the door on at 3pm, door thermometer read 600. By 6pm, it was down to 400, next morning read 275. Outside stayed at ambient, except for the stucco toward the front of the oven. It seemed like some steam was coming out from around where the stucco meets the vent.

Sunday, lit another fire, let it go low for an hour, then added enough wood to clear the dome, and put the door on after a total of 3 hours of fire. Door read around 675 when I put it on, 550 after 5 hours, and 400 this morning. Again the stucco toward the front of the dome was a bit warmer than ambient.

I can't figure out what's going on here. Prior to the last couple of firings, I was seeing the heat drop by 50-75 degrees per 12 hours, tops. It is possible that my door, always somewhat decrepit, has not been sealing well. I'm planning on rebuilding it soon...
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  #155  
Old 03-11-2013, 02:11 PM
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Location: Bungay, Suffolk, UK
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Default Re: 36" Pompeii in DC

Were the temperatures lower before?

The oven will not lose heat steadily.
Think of a graph line like a section through a skateboard halfpipe. Higher temps will reduce quicker, then more gradual as the oven temp drops towards ambient.
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  #156  
Old 03-11-2013, 02:13 PM
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Default Re: 36" Pompeii in DC

I think, because it is further away away from the direct dome fire, the moisture is evaporating at a slower rate, the steam can escape the insulation, since it gas, hence the heat build up. There nothing to worry about, just give it time.
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  #157  
Old 03-12-2013, 06:18 AM
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Default Re: 36" Pompeii in DC

Quote:
Originally Posted by Bookemdanno View Post
Were the temperatures lower before?

The oven will not lose heat steadily.
Think of a graph line like a section through a skateboard halfpipe. Higher temps will reduce quicker, then more gradual as the oven temp drops towards ambient.
I probably wasn't clear enough (happens a lot). The issue isn't that it went from 600 to 500 faster than 500 to 400--that's always been the case, nature of the beast, like you said. The thing is, for the first ~6 firings, the heat decay at any given temperature was about half as slow as it has been in the last two firings. What has changed in that time has been leaving the oven uncovered in the rain, and modifications to my door which were entirely for the worse. Leaving me puzzled as to what's going on.

Quote:
Originally Posted by Laurentius View Post
I think, because it is further away away from the direct dome fire, the moisture is evaporating at a slower rate, the steam can escape the insulation, since it gas, hence the heat build up. There nothing to worry about, just give it time.
That makes sense. So perhaps the rain never got through to the insulation in the first place. Maybe the culprit for heat retention is really just the door...
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  #158  
Old 03-12-2013, 07:30 AM
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Default Re: 36" Pompeii in DC

i believe that wood with too much moisture will not give as good a heat, than seasoned dried wood. If you were heating a "damp" oven and brickwork, i'd expect it to take longer to heat up, as you have to drive off the water. Perhaps it works in reverse also and your oven will return to the previous performance after its seasoned a little more with firings.
The water held within the brick, may act as a conduit for the heat to escape into the environment easier?
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  #159  
Old 03-12-2013, 12:21 PM
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Default Re: 36" Pompeii in DC

Quote:
Originally Posted by rsandler View Post
I probably wasn't clear enough (happens a lot). The issue isn't that it went from 600 to 500 faster than 500 to 400--that's always been the case, nature of the beast, like you said. The thing is, for the first ~6 firings, the heat decay at any given temperature was about half as slow as it has been in the last two firings. What has changed in that time has been leaving the oven uncovered in the rain, and modifications to my door which were entirely for the worse. Leaving me puzzled as to what's going on.



That makes sense. So perhaps the rain never got through to the insulation in the first place. Maybe the culprit for heat retention is really just the door...
Tell us about your door and photos too.
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  #160  
Old 03-13-2013, 08:11 AM
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Default Re: 36" Pompeii in DC

I've attached some pictures of my door. It's a piece (actually two pieces) of insulating board "wrapped" in aluminum, held together with stainless steel bolts. Because I (rather foolishly, in retrospect) didn't want to try rivets, the strip around the edges only has a couple of tabs, and so the aluminum on the front and back has warped with heat and abuse.

I tried adding a piece of fiberglass rope along the edge, but this was too large for the gap between door and arch. Thus, instead of having the aluminum front piece resting against the reveal of the entry, the rope was there. Between me not being careful enough about attaching the rope and my inner arch not being entirely straight, this resulted in a very imperfect seal.

Then the cement holding the rope failed in one place, and I just went ahead and ripped the rest of the rope off. Except some stuck around the base of the door.

My plan, when I get a period in between firings of the oven and don't have a bunch of other work to do around the house, is to take the door apart, and rebuild it. Instead of wrapping it entirely with aluminum, I will sandwich the insulation between two pieces of cement board. For the edges, I will take a piece of 8" aluminum flashing and cut 3" tabs all along to grib the insulating board. Since the cement board is rigid, my hope is that once they are bolted together, the pressure will then hold the flashing in place (this had been my thought for the aluminum, but of course aluminum sheet is too flexible).

Then, with the cement board sandwich fitting into entry arch somewhat snugly, I will mount a slab of wood on the outside to sit against the reveal. I'm contemplating getting some of that pour-in-place gasket material to make a tight seal.
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36" Pompeii in DC-20130312_172434.jpg   36" Pompeii in DC-20130312_172442.jpg   36" Pompeii in DC-20130312_172455.jpg  
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