I'm getting closer to my Dome!

[Aegis]

Re: I'm getting closer to my Dome!

Ive clocked the flue gasses through the slot for my damper in the chimney and they get to over 600c.

The bricks dont get this hot though, but I would imagine closer to the oven exit they may.

OH NO!!!!!!!! Brikie, you sparked a bad thought! Brick temperature!!!!!!!!
Hearth Brick temperature for sure!!!!!!!!!!!!!!!!! If the temperature of the flue bricks exceed the foamglas working temp of 900 degrees F then the hearth bricks under the fire will also???? so much for putting the hearth bricks on the foamglas.... Does anyone have their hearth bricks directly on the foamglas??? Is it ok???? I am going to be doing my hearth today, or so I thought! Help!!!!!!!!
Thanks in Advance
John

[brickie in oz]

Re: I'm getting closer to my Dome!

does anyone know how hot the chimney bricks get?

Ive clocked the flue gasses through the slot for my damper in the chimney and they get to over 600c.

The bricks dont get this hot though, but I would imagine closer to the oven exit they may.

[Aegis]

Re: I'm getting closer to my Dome!

I haven't worked with it myself, but I don't think it's up to direct flame/flue gas contact.

Thanks for the input, it sounds like you are correct given the following:

I looked up the spec sheet and it gives a maximum service temperature of +900 degrees F or 480 degrees C.
Since I have absolutely no fireplace/chimney experience, I guess my question is: does anyone know how hot the chimney bricks get? If it is over 900 degrees F then It is insulating firebrick for sure!
dmun, are you saying it gets that hot? It sounds like it could!
Thanks in advance
John

[dmun]

Re: I'm getting closer to my Dome!

I guess no thoughts on the foamglas heat break?????

I haven't worked with it myself, but I don't think it's up to direct flame/flue gas contact.

[Aegis]

Re: I'm getting closer to my Dome!

I guess no thoughts on the foamglas heat break?????
Well I will be starting work on the hearth tomorrow!!!!!! Yippie!!!!!!!!! First I will draw the outline of the hearth onto the bricks from my template. Number and cut the bricks to allow the walls to be on the outside of the hearth bricks. Then I will be laying a sand/fireclay base to allow leveling of the foamglas. Then on the foamglas another layer of sand/fireclay to allow leveling of the hearth bricks! I'm shooting for the hearth bricks cut and repositioned for the oven as the immediate goal. I'll post some pics as I go along.....

[Aegis]

Re: I'm getting closer to my Dome!

Mike, Thanks for the info and Helpful tips! I will attempt to incorporate them into the hearth for leveling. I am finishing up some back staircase from my deck to the patio/oven area. As soon as that is completed I will start on the oven.

I have a thought on heat breaking the chimney/flue area - Please everyone comment on the feasibility of this idea. I thought at the point of arch to flue transition, to install a 4" piece of foamglas for a thermal break between the arch and the chimney brick ascending. Can foamglas take this amount of heat? Otherwise I will go the insulating brick route like brikie did with his build.
Thanks
John

[SableSprings]

Re: I'm getting closer to my Dome!

Hi Mike,
I will definitely use the percrete mix, once I find perlite. Great photos!!!!!!!!!!!! THANKS!
John

I used two sources for perlite. One was the local Cement Block & Brick company. It had good sized bags (4 cu ft - 25#) for under $13 each. It was marked as masonry fill and consequently has a smaller average particle size with a light, silicone coating. I only noticed that silicone coating during the initial mix with cement, the cement powder washed off the perlite when I added water. (Remember to use a breathing mask, as when you are working with both the perlite and cement they both produce a lot of fine dust.) It quickly mixed back together and cured with all the strength I'd hoped for, so I didn't consider it a problem.

The other source was my local gardening supply. Their 25# bags were more expensive (at just under $20/bag). The particle size on the gardening stuff was probably 2-3 times larger and it doesn't have the coating. The cement did not wash off the perlite as easily and it mixed up easily (and seems to be equal to the smaller size perlite in cured strength). I mixed a wheel barrow full at a time, using a bucket to measure out 5:1 volumes of the perlite and cement. (Use a breathing mask!) Go slow on the water addition and don't make it too dry...I thought of it as along the lines of cookie dough. You've got to give it enough water to hydrate the cement fully.

[Aegis]

Re: I'm getting closer to my Dome!

Where, might I ask, did you find your thermocouples? I would love to plan on using as many as you, but they are so darn expensive. Are you using the thermocouples sold by FB?
Looking forward to seeing the results and progress of your build, as well as how the foamglass shapes up!!
Happy Bricklaying!
-Simon

Hi Simon, I purchased the thermocouples and hook ups through Omega.com.
Meter # DP7005 Price $83.00 (I would recommend DP7002 it is centigrade and runs on 115Vac-centigrade expands the top temp. You can read)
Thermocouple 5TC-GG-K-20_72 Price for 5 is $49.00
Extension Wire PR-K-24-SLE-50 Price is $32.00 for fifty feet

As for the oven build, it is still awaiting the finishing of the upper patio arae around the hot tub before I get back to full time oven. Hopefully by May 1st or sooner! Darn family functions get in the way along with a wet spring in N.E.
Hope this helps
John

[calipizzanapoletana]

Re: I'm getting closer to my Dome!

Yes I will report back with how well the foamglas works. I will be overkilling the thermocouple route with at least eight in various positions. Certainly above and below foamglas will be included and should give definitive data.

Where, might I ask, did you find your thermocouples? I would love to plan on using as many as you, but they are so darn expensive. Are you using the thermocouples sold by FB?

Looking forward to seeing the results and progress of your build, as well as how the foamglass shapes up!!

Happy Bricklaying!
-Simon

[Aegis]

Re: I'm getting closer to my Dome!

Hi Mike,
I will definitely use the percrete mix, once I find perlite. Great photos!!!!!!!!!!!! THANKS!
John

[SableSprings]

Re: I'm getting closer to my Dome!

I have been on your site and love your oven with the movable counters and great craftsmanship! Since I couldn't possibly eat more than 20 loaves per week and still fit through the door, I will lay the bricks flat as yourself and Dmun suggest will be sufficient. Did you use anything to contain the sand from migrating out from under your hearth? I was thinking more of a 1/4" of sand for leveling/stabilization would be all that is needed. The difference from the high to low spots is less than 1/4"
Again great oven and thanks for the info!
John

I added a layer of clay and diatomaceous earth between the firebrick dome and the perlcrete outer insulation-gives it a bit of slip and the fine powder fills in minor cracks in the refractory mortar of the dome. The perlcrete around the base is what I was using to keep the sand in place. During the build, the sand stayed pretty much in place on the edges of the perlcrete pad. When I moved to insulating the dome, the initial 3"-4" ring of perlcrete I poured/placed around the base not only locked in the leveling sand layer but allowed me to anchor the fencing wire that acts as an internal support for the insulation as I worked it over the dome. I did come back and put a second insulating layer of perlcrete to smooth out and reshape the dome outline before putting on the "brick barrel" facade.

(As for the 20 loaves--I do give most of my bread away to friends and neighbors so I don't have to widen my door frames or buy only clothing made of at least 80% spandex...)

[Aegis]

Re: I'm getting closer to my Dome!

I put my firebricks flat as shown in your pictures. I've baked 26 loaves on one firing and bake between 15-20 loaves once per week on average. The oven still has plenty of stored heat for cooking beans, roasts, ribs, etc. after bread so you shouldn't have any issues. I only used perlcrete for my bottom insulation, then an inch of sand for leveling the hearth bricks-will probably be the best way to make a quick leveling/stabilizing layer for both your foamglas and hearth bricks. The picture here show's my brother-in-law leveling my hearth. My whole build is summarized in photos at www.sablesprings.com or in The Dragonfly Den posted by sablesprings (in the forum's photo albums). All's well with my hearth brick levels after 18 months of fairly consistent weekly use.

I have been on your site and love your oven with the movable counters and great craftsmanship! Since I couldn't possibly eat more than 20 loaves per week and still fit through the door, I will lay the bricks flat as yourself and Dmun suggest will be sufficient. Did you use anything to contain the sand from migrating out from under your hearth? I was thinking more of a 1/4" of sand for leveling/stabilization would be all that is needed. The difference from the high to low spots is less than 1/4"
Again great oven and thanks for the info!
John

[Aegis]

Re: I'm getting closer to my Dome!

As the riggers say, gravity always wins. You're putting a lot of weight on top of this and I'm sure it will stay put without mortar. You don't want it wiggling, however. I'd use a little of your leveling medium under the foamglas to keep it steady.

Advise well taken, as soon as the rain stops I'll be putting down a sand base under the foamglas.

I'd only lay the bricks on edge if you were going for multiple-batch bread baking. Flat bricks for your floor seem to achieve the needed balance for pizza cooking.

I'll be doing some bread baking but only one load per firing, and I guess if I want to do more then a re-firing doesn't sound too hard versus having to heat up the extra mass on every firing.

Let us know how the foamglas works out. It's a lot more affordable than refractory insulation, and a lot less work than mixing vermiculite concrete.

Yes I will report back with how well the foamglas works. I will be overkilling the thermocouple route with at least eight in various positions. Certainly above and below foamglas will be included and should give definitive data.
Thanks for the input!

[SableSprings]

Re: I'm getting closer to my Dome!

I put my firebricks flat as shown in your pictures. I've baked 26 loaves on one firing and bake between 15-20 loaves once per week on average. The oven still has plenty of stored heat for cooking beans, roasts, ribs, etc. after bread so you shouldn't have any issues. I only used perlcrete for my bottom insulation, then an inch of sand for leveling the hearth bricks-will probably be the best way to make a quick leveling/stabilizing layer for both your foamglas and hearth bricks. The picture here show's my brother-in-law leveling my hearth. My whole build is summarized in photos at www.sablesprings.com or in The Dragonfly Den posted by sablesprings (in the forum's photo albums). All's well with my hearth brick levels after 18 months of fairly consistent weekly use.

[dmun]

Re: I'm getting closer to my Dome!

As the riggers say, gravity always wins. You're putting a lot of weight on top of this and I'm sure it will stay put without mortar. You don't want it wiggling, however. I'd use a little of your leveling medium under the foamglas to keep it steady.

I'd only lay the bricks on edge if you were going for multiple-batch bread baking. Flat bricks for your floor seem to achieve the needed balance for pizza cooking.

Let us know how the foamglas works out. It's a lot more affordable than refractory insulation, and a lot less work than mixing vermiculite concrete.