If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.
(M) Hope wrote that "The ceramic insulation blanket cost 94.00 for 50 sq feet."
(M) That seems kinda "spendy". Why couldn't we simply lay out standard fiber glass batts, or rolls on top of our ovens and then, optionally apply insulating mortar covered with stucco ?
(M) I have seen many photos where builders constructed a shell of Durock or Wonderboard (a cement board) around their "igloo". Then they poured vermiculite or a similar insulation into the box they created that houses their igloo. Isn't that a lot cheaper?
"Everything should be made as simple as possible, ...
but no simpler!" (Albert Einstein)
The ceramic insulation blanket cost 94.00 for 50 sq feet.
You can get the same thing now on EBAY for 53 dollars plus shipping. Just search for "Kaowool".
My understanding is that when tyhe whole dome gets really hot the fiberglass melts. The Kaowool can withstand up to 3200?.
You can just pour vermiculite around the oven. The logic behind the insulating blanket is that it is more efficient than vermiculite, so it does a better job of keeping heat inside the oven. It keeps the thickness of the insulation down. It is also a solid blanket, that will keep anything, such as sand or loose insulation, from ever working its way down through your brickwork and falling into the oven.
Like most things in the Pompeii design, you get to choose, we just give you the information you need to make the choice. :-)
The $53 for 50 sq ft is a good price.
We stock Insulfrax 1" at Forno Bravo. You can always get it from us, though you have to pay shipping.
If do you prefer to use the fiberglass blanket to replace some of the vermiculite layer, you simply could change the order of work, as dome refractory bricks ? mortar ? vermiculite ? fiberglass ? stucco (finishing).
The vermiculite installed after mortar, down the temperatures reaching the fiberglass.
I made this in my hearth building (fiberglass ? vermiculite ? mortar ? sand & clay ? refractory bricks) and I had not experienced any problems.
I installed several thermocouples on the hearth surface, between this and mortar and below the fiberglass. The temperature curve of this last one show no variation in the first 3 hours or so (fired and cooking pizzas time) and an elevation of around 120 ?F over the next 12 hours (closed door, no fire at all).
I?ll try to clarify myself.
When I begun to built the oven, it grow up with the walls and I made the slab too (this means tooooo) big and surrounded by the walls. Then, I realized that this was a looot of thermal mass that would spend an eternity to be as hot as necessary. I faced with two solutions, discard the entire work and begin again (what could I did with a 3?x3?x1? concrete/vermiculite broken mass on my backyard?) or build a entirely new slab over this old one. I decided by follow the second option.
BTW, I introduced other changes and went from barrel oven to domed one (Jim, James and folks were my inspiration and help, thanks again).
At this point I had a heavily concreted ?table? that could not to be a ?temperature drainer?.
I follow the slab construction as explained in the last reply, this is, from lower to upper, over the ?concrete table? I put a alluminium sheet, followed by the fiberglass, then over it 2?of 8-1 vermiculite/cement mixture (isolation) and the 2? of concrete as thermal mass (isolated isle), finishing with the oven brick hearth resting on sand/clay.
I think that the above process is clear in the last reply pictures.
The thermocouple is located exactly in the middle of the circular hearth and below the fiberglass (between the fiberglass and the alluminium sheet).
The oven, when fired, take near of 1 to 1 ? of hour to reach the temperature to cook pizza and more two hours or so making several ones.
Before that, the dashes are retired, the oven floor is cleaned and the door is closed (if no cooking anything more).
The results are in the annexed archive (any one picked) in ?F.
You could see that the line that shows the lower thermocouple is practically horizontal!
PS: Sorry ?Abajo toda isolaci?n? means ?Below isolation?, that is ours.