Hearth Floor

[james]

Re: Hearth Floor

I'm assuming that when James says we're not filling the floors as it is, the dome is 1000F near the end of firing, the floor is somewhere below that (800?) and as the initial "plasma" phase dies out the respective temps equalize.
Mark

Mark, that's not quite it. Typically you can fire the dome and floor to roughly the same temperature.

Think if the floor (or dome for that matter) as having both inner and outer facing edges. When the inside of your oven is hot, let's say 800?F on both the dome and the floor using an infrared thermometer, you are measuring the inner face. The part facing the fire. At that point, the outer face will be much cooler, depending on how quickly you fired up your oven. From that point on, you can continue firing your oven, and the inner face will stay roughly 800?F, and the additional heat will continue to drive up the temperature of the outer face of your dome and floor. That's the stored heat you use when you bake without the fire.

Alternatively, when the inner face of your oven is hot and the outer face is still cold -- and you take out the fire -- the two faces of your oven will meet in the middle to the point of equilibrium, and the entire mass will become only moderately warm. The inner face will cool down and the outer face will wick heat outward.

That's what I meant by "filling" your oven with heat. I tried to capture that with our FB heat graphic.
James

[MK1]

Re: Hearth Floor

Okay now I get it. I took a closer look at the graphic above and included in the plans. It clearly states that it's showing how the heat moves to the outer edge of the mass. I had read that but didn't have enough background to understand. It takes me a little while. Again I appreciate all the prototyping you've done, and I can't wait to fire it up.. that is, after I finish building it.

Mark

[jbergen]

Re: Hearth Floor

I've been researching the "island hearth" comments on the forum, and I wonder if what I'm reading from 2009 or so is the final & best answer. We're building the oven with an interest in baking bread. Has it been determined that the 2" floor tiles supplied in the FB kit are adequate, or should I still consider adding 1 1/4" splits under that floor? (and then the rigid ceramic insulation under that)

[Brodek]

Re: Hearth Floor

jBergen,

In the same boat, so they say. Want to build my oven for bread first, and pizza as a nice Friday night side...with a target of Saturday morning baking. Only one or two bakes, because how much bread do we need?

I originally was convinced (by self) that the Allen Scott oven was best...but after a LOT of reading/research I may have been pursuing too much "mass", rendering the firing/heating into a too-long process. Again, I'm not going to bake all day, but I would like enough mass to handle baking the morning after a pizza event.

My current thinking and questioning is whether I should add ceramic fiber board over my 4" vermiculite layer (Econolite) and use the fire bricks on their sides for my floor mass. Or, should I lay the floor directly on the vermiculite layer and lay them flat or on their sides? I haven't been able to really find exactly the answer... And, I won't even get into the "should I change to an igloo shape"... thought-track.

Never expected this to be easy...but thought I could make a decision!

Will be following this thread closely to see what ideas emerge.

Kevin

[jbergen]

Re: Hearth Floor

You might find part of your answer over in another thread
http://www.fornobravo.com/forum/f2/n...rta-21667.html

[Greenman]

Re: Hearth Floor

The bottom line really is how much of what you are going to use if for. If you have the hearth isolated by insulation then the basic plans are quite efficient enough to cope with normal domestic requirements.

Mine is an 'igloo' built on 4" of vermicrete, the bricks of the hearth laid on the flat and the dome built with half bricks then insulated with ceramic fibre and then more vermicrete before the render layer.

It heats up in an hour and a half and maintains useful heat for a couple of days after which it takes little to bring it back up to temp.

I think that the trap can be to over-think the whole process. Lots of good builds to draw ideas from here but most of them are built to the FB plan or with minor variations from it.

Good luck with it.

[jbergen]

Re: Hearth Floor

Thanks, Steve. Great pics, BTW.