Ellie's WFO as it it built

[Ellie]

Re: Ellie's WFO as it it built

Nope you are right, I am confusing the two. Dale and I looked at the plans again... my fault for not researching more thoroughly here. He is such a good guy. He thinks it is ok the way it is, but says it is up to me. For my comfort level, we agreed to put the blanket on it and one coat of mortar over that..... the stuff I found is not going to work, it is too small. We are having a heck of a time finding the right stuff to do it with.

You are all so kind. Even when I am not understanding things, and am dead wrong on some, you point it out ever so gently. I appreciate that.

Question: if we cannot find the ceramic blanket, can we just use the vermiculite mixture to go over it? Would this work as enough insulation?

Ellie

[egalecki]

Re: Ellie's WFO as it it built

Nikki and I cross posted!

[egalecki]

Re: Ellie's WFO as it it built

I may be wrong, but it seems as though you have thermal mass and insulation mixed up a bit. Thermal mass is what you are heating up- the part that does the actual cooking later. The insulation is what you need to keep the thermal mass hot longer, so you can use less fuel and maximize the potential for retained heat cooking. Bricks and mortar don't insulate (unless the bricks are a special insulating brick), and, in fact, will make it take longer to heat up the oven, since they add mass.

If you have the proper insulation (vermiculite, vermiculite concrete or insulating blanket) between the layers of firebrick and the outer layer of brick, then you've isolated the thermal mass of the firebrick from the outer layer. No problem there. We just aren't sure that your batt insulation with the paper off is going to adequately do that job. It'll still cook pizza, but it'll take you longer to heat it up and it will cool off quickly and you won't get the ability to use the oven for several days on one firing. That's all.

Please add the insulation if it's at all possible. You'll be happier in the long run.

Forgive me if I'm wrong about the confusion. It just read that way to me.

[Modthyrth]

Re: Ellie's WFO as it it built

Thermal mass is different than insulation. Thermal mass is the material--firebrick and refractory mortar and such--that soaks up and radiates the heat. The insulation is the stuff outside the thermal mass that keeps the heat where you want it (in the oven) instead of leaking out. The plans call for ceramic blanket or vermiculite or perlite mixture, but I'm certainly very curious to know how the house insulation works! Have you fired up the oven yet for curing to see how the insulation reacts?

I'm not sure if we're dealing with a simple typo/word-mixup here (in post #61) or real confusion that's going to affect how your oven performs. Exterior cladding, outside of the insulation layer, is not considered adding to the thermal mass of the oven. You're certainly right that you don't need any more thermal mass. We're just a wee bit worried about the unconventional insulation.

[Ellie]

Re: Ellie's WFO as it it built

Well, I found in the plans on page 38 "You do not need to add thermal mass to your oven at this point, because the mass of he bricks adn the mortar you have used to hold it together are more than sufficient for backyard pizza baking or even restarurant pizza baking for that matter..."

This is after completing the dome.

We are adding brick to the outside of the dome as well, so I think we have enough insulation at this point. I am talking with Dale this morning to make the decision whether to put the thermal blanket over the thing before the bricks or not...

Ellie

[tdibratt]

Re: Ellie's WFO as it it built

The ceramic blankets are typically secured similar to the way you did the first layer. Using chicken wire over top. I used bricks around the perimiter and on top until I started to coat it with the vermicrete mixture. Once the vermicrete went on I removed the bricks that were just there to keep things together until the vermicrete went on.

I am not sure about leaving the first layer on, you may want to fire it up gradually. You do not want to drive it hard and have everything crack on you. So fire it up slowly over the period of a week or so getting it hotter each day. And see if that insulation does not produce any ill side effects.

If you go ahead with the blankets and find that it fails, I am not sure what it might do.

Regards..

[Ellie]

Re: Ellie's WFO as it it built

Hooray!! I found the blankets. Actually, they are pretty expensive and don't come in rolls like the ones I saw on the internet.

These are 24x32 or something like that. They are one inch. They had that and 1/2 inch ones. I got two and that will have to do at these prices.

How do you secure them to the dome?

Thanks,
Ellie

[Ellie]

Re: Ellie's WFO as it it built

Well, I better go back to the drawing board. I will confer with Dale and see what we can do. He has already put the mortar on it.

I guess the only recourse is to leave it sandwiched in between the layers of cement/mortar. Then, find the blanket (that has been the issue) and put it over this last layer and add another layer of mortar.

I mean if it burns, it is not going anywhere.

Ellie

[MAVANO]

Re: Ellie's WFO as it it built

best thing is to add 1-2 inch ceramic blanket than wire and mortar I dont think that regular house insul. is for high heat

[Les]

Re: Ellie's WFO as it it built

we did not need to add any insulation to the dome once it had the refractory mortar on it.

Ellie,
I believe you are mistaken - you DO need to add insulation to the dome. Am I misunderstanding what you mean?


Les...

[Ellie]

Re: Ellie's WFO as it it built

Now, I don't remember. I do know that in reading the plans, we did not need to add any insulation to the dome once it had the refractory mortar on it. If that is the case, then it may seem that adding a layer of insulation and more mortar should not hurt it. Now, of course, I have to start worrying, which I do well!!

Ellie

[egalecki]

Re: Ellie's WFO as it it built

Ellie, what did you read that said it was ok? I'm not so sure. Rockwool (which I think some people have used) isn't as good an insulator as insulating blanket, but it's ok. Rockwool isn't the same as the pink stuff, though. It would be a pity to get it all done and discover that it isn't what you need.

Can you leave it where it is for a while, let it dry out a bit, cure it and test it? That way if it isn't enough, or if it melts or something, you can fix it without tearing your hair out.

[Rastys]

Re: Ellie's WFO as it it built

More fool you for getting your hands in what is known as a very hot oven eh!

Rastys

[gjbingham]

Re: Ellie's WFO as it it built

Good point dmun. Has anybody measured the temps on the outside surface of the dome bricks while the interior is 900 or so degrees? I wonder weather regular home insulation, sans paper, can withstand the exterior dome heat without eventually looking like the singed hairs on the back of my hands after a night of making pizza.

[dmun]

Re: Ellie's WFO as it it built

We eagerly await results of the house insulation experiment: you might want to hold off on fabulous surface treatments before you find out if the house insulation will hold heat and keep the exterior cool enough not to be a hazard.