Oven floor design: thickness & insulation

[mannextdoor]

Re: Oven floor design: thickness & insulation

This thread was very big help to me. Just starting to build my WFO. It's always better when you employ the 5P's. Prior Planning Prevents Poor Performance.

Mannextdoor

[Xabia Jim]

Re: Oven floor design: thickness & insulation

I'm with you george.....but I do prefer the hot butt from the hot rocks under the sun!

[gjbingham]

Re: Oven floor design: thickness & insulation

Good post Vincent!

I did 9 pizzas tonight. The party was delayed by an hour - the oven heated for 2 full hours. The heat retention is much better, in fact, overly so. Four hours later I was still waiting for cooler temps to put Kaiser rolls in the oven.

The pizza was superb tonight. Good comments all!

XJ - think of heat as simple energy. It takes energy (read - fire in this case) to make the sustrate (oven) hot, and subsequently colder surfaces around it absorb it. It runs downhill like water, higer energy to lower energy, hot to cold. Never cold to hot. Hence, you get a cold butt on a cold rock!

[james]

Re: Oven floor design: thickness & insulation

... I buy my firewood split and delivered which i then have to split it even smaller. Its generally oak or ash which burns very hot. When i want increased oven temps i use pieces that are only about 2 inches in thickness. i also use a small axe to shave off the bark. There isn't really any BTU value in it and if the wood is stored outside it has a tendency to wick moisture. Its worthless and slows the fire down. I have found that feeding the fire in this manner the oven temp quicky increases and becomes easily maintained. One last thing. Properly seasoned wood is critical.

This is excellent, excellent advice. Right on target -- and what a difference it makes when you do it right.

Maybe we should move some of these postings to Fire Management.
James

[vincent]

Re: Oven floor design: thickness & insulation

Although i haven't built my oven yet i believe that i can give a bit of advise on a hot fire. My wife and i cook most of the winter with a 1936 Kalamazoo wood fired stove. The fire box is very small. Its easy to get the cast iron top hot but the oven is different. It requires a hotter and constant burn. I buy my firewood split and delivered which i then have to split it even smaller. Its generally oak or ash which burns very hot. When i want increased oven temps i use pieces that are only about 2 inches in thickness. i also use a small axe to shave off the bark. There isn't really any BTU value in it and if the wood is stored outside it has a tendency to wick moisture. Its worthless and slows the fire down. I have found that feeding the fire in this manner the oven temp quicky increases and becomes easily maintained. One last thing. Properly seasoned wood is critical.

[Xabia Jim]

Re: Oven floor design: thickness & insulation

Great thread!

Dmun says heat rises. I think statement is entirely coorect wrt heat in air. My oven's stand gets warm by the next day, so heat certainly sinks towards cooler areas as well. !

Cold is the absence of heat...I notice that any of the masonry in touch with the oven eventually warms up as it wicks away heat. (particularly after 5 days cooking)

My first oven was to be a cooking oven and the thermal mass was intentional....but after the FB addiction "I want Pitha"

[Xabia Jim]

Re: Oven floor design: thickness & insulation

I would also like to add, if you have the opportunity to get your hands on some seasoned citrus, jump on it. There is a pretty big learning curve because it burns so long and hot
RT

Interesting, my spanish friends told me the best wood for Paella was orange wood....I'll need to try that!

[RTflorida]

Re: Oven floor design: thickness & insulation

Keeping a bigger fire (not huge or scary) has been a big help to me. I started out letting my fires die down too much ,I think. I've never had issues with logs catching once I 've reached the high temps, they DO catch almost instantly. My problem was not keeping at least one good, fresh log on the fire...doing so has made a big difference recently.
I would also like to add, if you have the opportunity to get your hands on some seasoned citrus, jump on it. There is a pretty big learning curve because it burns so long and hot (my first fire I thought the whole oven was going to melt), but my wood consumption is literally 1/2 of what it is when I use oak or hickory. Maybe the citrus is the reason I am having no problems with hearth temps dropping after several pizzas...probably a combination of the changes I've made, I'm not sure.

RT

[james]

Re: Oven floor design: thickness & insulation

Hey George,

You should be able to add a smallish piece (2-3") of wood every 15-20 minutes, and have it combust pretty much on impact. That way you add flame and heat, without damping the fire until the new piece catches.

What do you think? A bigger fire? Of perhaps slightly smaller wood, so that it is ready to catch fire? More aged wood that is ready to catch?

Good thread.
James

[gjbingham]

Re: Oven floor design: thickness & insulation

Great thread!

Dmun says heat rises. I think statement is entirely correct wrt heat in air. My oven's stand gets warm by the next day, so heat certainly sinks towards cooler areas as well. Ever sit on a big cold rock? It's not the rock that makes your butt cold, but the fact that heat flows from warm to cold, and you actually loose heat to the rock, and your butt gets cold.
In a well insulated and closed oven, the heat has to go somewhere, otherwise the oven would stay hot for eternity. While I didn't build a perfectly thermodynamically perfect oven, I'm still not happy with the way the oven floor cools so much faster than the dome. I'll keep working on moving my fire to the side so that it keeps burning hot. Seems like when I move it over and add a log, it burns hot for about 10 minutes then afterward, is really hard to keep the fire going really hot. Probably just poor oven management.
Comments, recommendations? As I said, gread thread! Thanks!

[RTflorida]

Re: Oven floor design: thickness & insulation

James, good point about keeping a good fire going throughout your pizza bakes; I always have, but lately I have kept a bigger fire (basically because my current batch of logs are larger). On a couple of my earliest multiple pizza bakes, I had to do exactly as you mention - pull the coals back over the cleared area to recharge.
Another point I've learned - letting my oven "charge" a little longer after it burns white. Initially, I waited 10-15 minutes; now I go about 20. No more issues (as of late) with the hearth cooling down before all of the pizzas are done.

RT

[dmun]

Re: Oven floor design: thickness & insulation

I saw a video, I forget where, of That Famous Pizzaria in Naples. Under the oven there was a pile of dried wood chips, which of course would flame up much more quickly than logs would.

I've been surprised how much heat comes from above. You can put chops in the oven and grill them on top just like in a broiler. The bottom, on a rack, hardly browns at all.

[james]

Re: Oven floor design: thickness & insulation

One more thing I would like to add on floor thickness and keeping the cooking floor hot. I've read lots of postings, talked with people and experienced first hand the challenge of keeping the cooking floor hot when you cook lots of pizza for a party.

Along with keeping your floor the right thickness -- about 2 1/2" and insulating it well, I want to mention how important it is to keep a good fire going the whole time you are cooking. A serious flame lapping into the top of the dome or more. You should never have to stop cooking and drag the fire back over the oven floor to recharge it.

If you picture the Modena G gas-fired oven, it helps make the point. That oven has a monster burner that allows it hold 800?F in the dome and floor, so that it can bake 90 sec - 2 minute pizza all day long, without stopping. What I think it interesting is that the floor is fully heated by heat reflecting off the dome and bouncing down onto the floor. It never has a fire started in the middle of the floor and moved to the side. For me, that really underscores the importance of having a good fire while you are baking pizza.

So next time you have a big party -- keep a good flaming going the whole time you are cooking.

James

[dbhansen]

Re: Oven floor design: thickness & insulation

Thanks dmun, I appreciate the input and feel more confident in my design decisions.

I have 2 1/2 inches of insblock19 under my brick floor, which is a less effective insulator than cal-sil, and my slab never gets more than warm to the touch.

More won't hurt, but after all, heat rises. I'd go for more blanket on the top if you have spare change in your budget.

[dmun]

Re: Oven floor design: thickness & insulation

I have 2 1/2 inches of insblock19 under my brick floor, which is a less effective insulator than cal-sil, and my slab never gets more than warm to the touch.

More won't hurt, but after all, heat rises. I'd go for more blanket on the top if you have spare change in your budget.