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happy 05-06-2010 01:22 PM

please help the new guy
hello to all from hampstead NC.

so i've almost fully completed my oven. last night i cooked the best pizza. And now for the problem....I lose heat due to not reading this forum:( .Ihave 4.5 " of concrete with no vermiculite under fire brick. so theres the problem. after reading some and talking with a local oven builder he suggests puring 5.5" vermiculite forms getting them under the oven floor and sticking them up with firebrick mortor. This idea sounds as best a can be done. how does this sound to anyone else. at this point the wind has been takin out of my sail any help would greatly be appreciated. im also considering chisiling out fire brick laying the 3 inches of vermiculite and trying to set bricks back in. second option will probably be tougher being my entry is 13".

thanks in advanced

Rodway Plazza 05-22-2010 12:30 PM

Re: please help the new guy
I am having the same problem, see the treads called'' I am losing heat like a water out of a tap''..........
It may help?

texassourdough 05-22-2010 02:38 PM

Re: please help the new guy
Hi Happy!

Part of the good news is that every oven is different and many are not ideal. In your case I don't think it is nearly as bad as you seem to.

I built my oven just as FB was getting going. I had planned to build a barrel vault/Scott oven and had did my base plans based on Scott. As a bread oven designer he put the cement above the vermculite to give it more mass/retain more heat rather than the FB recommendation of putting the vermiculite on top of the cement. oven is a lot like what you seem to be describing - a pizza oven on an insulation below cement floor. The difference is that my cement layer is a bit thinner about 3 3/4 inches thick.

The key difference between my oven and normal is that when I do pizza on a short burn - about 45 minutes to clear and 15 minutes to heat soak before doing pizzas, the hearth will slowly cool over time as heat dissipates into the cement (faster than it is being replenished by the fire). It isn't bad. I just rake the coals out every half hour or so for five minutes to refresh the surface temp of hearth. Has the advantage of taking care of any spills too!

I think his idea is a much easier solution than chiseling out... And you will have lots of mass in the hearth for bread!

Good Luck!

Jed 05-22-2010 09:28 PM

Re: please help the new guy
Hey Jay,

How long will you burn a fire to get your oven ready for a bread bake? Do you need to keep the fire going for 'day's' to get your oven (and the supporting slab) up to temperature? (I remember from Allan's book he would burn the fire first one day, and then the a second fire on the second day to get his oven heat soaked for a multiple batch bread bake...)



texassourdough 05-23-2010 06:24 AM

Re: please help the new guy
Hi Steve!

I know I have somewhat higher hearth heat loss than the typical FB oven built by current standards. IF I wanted to build it this way today, I would put a heat break around the hearth - probably using a form to allow me to put cement under the hearth (and over the vermiculite insulation) and vermiculite cement as a break surrounding the cement on the four sides. - which I think would work pretty well and would be an improvement on the standard Scott design. (I might also only make the cement 2 inches thick...or so but that might be a mistake!)

My dome is an FB casa shell and hearth with an extra inch or so of refractory cement to add mass. I have plenty of mass for double batches but not enough for the typical Scott three/four/or more bakes.

I have only done a double bake once so I am not fully knowledgeable of my oven on this regard. I fired it for about 3 1/2 hours, cleared the oven, closed it off and an hour later it was about 600 degrees on the hearth and 625 on the dome. About a 45 minutes later it was about 575 and 600. I think opening/closing the oven and the hearth were the primary sources of temp decline.

I loaded a 14 pound batch of bread and baked for about 50 minutes total. At that point the hearth was about 435. Closed it up. A half hour later it was back to 485 and I put in a second batch. That took about an hour and the temp was about 410 at the finish.

My conclusion is really simple. IF you want to do multiple batches of bread as a regular practice, the Scott is the way to go. If you only want to do one batch with an occasional second, the pizza oven (especially with extra mass) works well.

WRT firing. I suspect longer firing would be good. My oven was a bit wet last weekend so I fired it for four hours on Saturday (and left the coals in so it stayed hot all night). And then fired it again on Sunday for an hour or so and it was spectacularly loaded. We did pizza but it was obvious that it would have been great for bread.

An important factor in all of this is oven dampness. Ovens used periodically will tend to be wetter than ovens used daily and therefore lose heat faster until dried back out.

For a single batch of bread, I burn for about 2 to 2 1/2 hours. The oven definitely isn't fully loaded but it is loaded enough that I can do one batch and not have the temp fall too far. (I have done bread on 1 1/2 hour burn and it worked too!) I don't think an hour would reasonably work - temp would drop too fast.

That's more than you asked for but I think provides a fairly complete answer/response to what you are asking.

Good Luck!

Jed 05-23-2010 08:50 PM

Re: please help the new guy

Thanks for the detail... I sort of high - jacked this thread, but the information may be helpful for happy to decide how he wants to proceed with his oven...

I built to the Pompeii plan, with out using any factory issued insulation, so perlcrete top and bottom. Pizza is great, one load of bread is great, then it is on to cooking things that require less heat... And I think for our situation, that is a good combination. As a good American, I will always want "more", but I get "enough" retained heat with the oven as built.

I typically burn a fire for an hour and a half to two hours before putting the door in place and smothering the fire, preparing to pull the coals and bake. I have not experimented with a longer fire to see if I can load up the oven with more heat! An experiment for some time in the future.

As yet another aside, I baked two types of bread this am in the wood oven for an afternoon potluck. A sourdough with 1/3 whole wheat, and 2/3 unbleached white flour, and a sourdough whole grain combination, wheat, oat, rye, with seeds on top. Both breads came out just fine, and I was pleased..

The occasion was unique... A wild food potluck..

On the menu was elk, moose, pheasant, javalina in the meat department - prepared in several different ways - grilled, marinated, sauteed, and in stews. In the vegetables, one guy cooked up nettle with a mint sauce; Morels are in season so we had Morels three ways (all to die for), cat tail stems, and a fresh green salad with a variety of stuff I didn't catalog. No one left hungry - a fine collection of cooks in the group (some of the dishes were prepared in the cast iron over charcoal).

Anyway, a fun event worth a short report..

See you,


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