36" Pompeii in DC

[V-wiz]

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)

[deejayoh]

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!

[Laurentius]

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.

[rsandler]

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...

[Bookemdanno]

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.

[Laurentius]

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.

[rsandler]

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.

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.

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...

[Bookemdanno]

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?

[Laurentius]

Re: 36" Pompeii in DC

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.

[rsandler]

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.

[rsandler]

Re: 36" Pompeii in DC

With the advent of spring, I've been doing a bunch of work on the oven (or rather, its surounds).

First, I re-built my door, such that instead of warped aluminum, the insulation is now sandwiched between two pieces of Hardiboard, with aluminum flashing for the edge, and a decorative wood front. The wood sits nicely flush against the inner reveal. Despite this, on my first use of the new door, the oven dropped from 550 to 300 overnight :P. I can't figure this thing out. I'm still getting the front of the oven feeling warm through the insulation and stucco--maybe there's still moisture being driven out?

I've also been working on the prep table next to the oven and countertops for the oven landing. Dry stacked concrete blocks for the support, bent rebar to go from corner to corner, then poured a 3.5" slab and filled the cores in one go. I got a small Harbor Freight cement mixer as a birthday present, and it made the work go fast.

Also poured a 24"x49"x2" slab for a polished concrete countertop to go on the prep table. The concrete mix ended up being way stiffer than I expected, yielding lots of voids, both because of air gaps and the fact that it pushed the crushed glass into clumps. Said clumps either had big voids around the edges of the glass, bigger voids where a bunch of glass fell out, or both. The attached picture is from after demolding and grinding with a 50 grit diamond pad. This weekend I went up to 400 grit and added (a lot of) slurry--hopefully it will smooth out and the filled voids will give it a nice veined effect.

I also have been working on countertops for the oven landing. Started by building up the landing so that a ~2" countertop would be flush with the oven entry. Did this by mortaring in bricks along the edge of the structural slab, and then pouring concrete into the enclosed space once the mortar had set. Then I screwed the forms for the main countertop into the bricks using masonry anchors. Poured the countertop yesterday after the last picture was taken--I'll start polishing this weekend and hope for the best.

Now that the work surfaces are nearly done, I'm planning on a big pizza party for early May

[ATK406]

Re: 36" Pompeii in DC

Nice to hear from you. The weather must be considerably nicer in DC than here in MI. What is the advantage of placing your countertop in a separate form vs formed onsite? I know it can be done both ways but I haven't heard or read a convincing Pro/Con comparison of the two techniques. Knowing that you always do your homework first, I wonder what you have found.

Always look forward to seeing progress on your project. Nice work...I think the blue glass/cement countertop will look spectacular when finished.

Regards,
AT

[rsandler]

Re: 36" Pompeii in DC

AT: Spring was somewhat slow in coming (or so I am told by my co-workers who have lived here longer), but it has been lovely the past few weeks. Highs in the low 70s all weekend.

On the countertop forms, I dithered back and forth a lot, and in the end the deciding factor was idiot-proof-ness. Pouring "face down" in a form gives you a smoother surface before you start polishing and gives you more control over shape and size--it's much cleaner and more straightforward to have the countertop make a slight overhang, for instance. Although my slab ended up pretty craggy because of the stiff mix, the bits without glass bear out the argument about smoothness--if you were okay with a matte surface, you could probably skip polishing entirely.

In principle pouring face down would help the placement of decorative aggregates like the glass, although that didn't work out so well for me :P. All this meant that for the prep table, which was just a simple rectangle, pouring in a form left the least room for error.

For my landing counters on the other hand, I had a much more complex shape, since I wanted the counters to fit around the vent area and wrap around the sides of the igloo. Possible you could build a form to do this, but I would surely mess that up. I was also paranoid about getting the countertop the right thickness--I wouldn't want the countertop to go above my entry bricks. As a compromise on getting the countertop to do a nice overhang, I screwed a 2x4 to the bricks in the front and mounted the melamine form on that, while the side pieces are screw directly into the brick.

If I had an enclosure (and thus was doing just a simple rectangle for the landing counter), I would have done a face-down pour for both, but this seemed like a pretty good compromise.

[rsandler]

Re: 36" Pompeii in DC

Lots more work on the counters. Pics attached for the prep table.

This didn't turn out at all how I expected, but I'm really happy with the results. The bright orange color of the slurry was the result of me mistakingly thinking the slurry would lighten as it dried. Word to the wise: slurry made with white portland cement does not change color when it dries. Live and learn... Still, the brown/orange/blue mix, actually works. As my wife put it "I know that wasn't what you were trying to do, because I can't imagine you trying for orange, but it actually looks pretty cool."

I shelled out for the Cheng brand sealer, which after two coats keeps moisture out of most of it. Also applied a very thin coat of Cheng wax before I got fed up with the cheap buffer bonnet I bought and called it good enough. I did discover that after a couple days of constant, drenching rain there were a few spots that "wet out" despite the sealer. Wondering if I should buy another bottle of sealer and re-seal, and if that will even work through the wax. I guess if water gets through, the sealer should too, right?

Pics of the landing counter to follow...

[rsandler]

Re: 36" Pompeii in DC

And here's the landing counter, pics attached.

I'm satisfied with how the landing turned out, but not nearly as happy as with the prep table slab. If I had it to do again, I'd have figured out some way to pour it face down. In part because it was hard to screed and in part because I'm a lousy hand with a trowel, the initial surface was very rough, and uneven to boot. Even after two slurry coats, there were still a bunch of dings and divots that I just gave up on. On the other hand, I can already see that the landing will frequently be coated in ash and gunk from the fire, so maybe I shouldn't worry about it too much.

I ended up continuing the orange them here, although again unintentionally. This time I knew that whatever color the slurry started would be the color it stayed, but the slurry looked browner in the mixing tub, and turned orange as I started rubbing it in :P. Ah well, now I've got a them. And it goes with the terracotta red flue tile. If I admitted that I goofed on the color, you'd think I planned it.

I guess now the tile mosaic for the dome will need to use those colors: brown, orange and flecks of blue. Any suggestions on designs?

The finished product: