#11  
Old 12-01-2010, 07:51 AM
Il Pizzaiolo
 
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Default Re: Tall fire, yes. Wide fire too.

Hi John/Kim!

By heat load I mean extending the burn to push heat into the refractory and cladding so that there is heat available in the mass of the oven to "ooze" back to the oven and bake the bread. If you only heat the oven until the surface is at temp you will chill the oven with the dough (and open door) and it won't bounce back to the temp you want for baking.

You got great color for only 7.5 pounds of dough Kim. Nicely moist oven. There IS a balance between the amount of bread you bake and the amount of dough you put in the oven. (And every oven is a bit different!) Example: One loaf would barely cool the oven and would burn at 565. A full load (say 15 pounds) will probably knock the temp of the air in the oven well below 200 and the hearth to near 212 at the surface where the loaves are and 300 to 350 (maybe 400) where it is bare. The dome will drop somewhat but not so much. It is the heat you loaded into the refractory that somewhat gradually heats the oven back up to baking temp around 450 when the loaves are done. Then when you take those loaves out the oven SHOULD heat on up to over 500 or so (ideally 525 to 550 in an AS oven) so you can do a second load (of different breads for the temp won't be as hot). IF you are only doing one load this is obviously les significant but if your oven doesn't heat up after you remove the bread it wasn't very well heat loaded and your bake is probably impaired.

Swabbing before loading the bread is always good for it helps increase humidity. I don't personally recommend spraying artisanal loaves so I try not to spray directly on them though I do spray up into the dome...

The challenge John with the soapstone hearth is that it tends to conduct heat faster than refractory so the bottoms can scorch. You may need to use a somewhat lower hearth temp - perhaps even 500 or so and even that depends on the dough load in the oven. The dome/hearth balance is not easily managed. It will be what it will be. You just have to find the temp that gives you the results you want. As indicated before, getting sourdough and oven to peak at the same time takes some experience and practice. Consider doing yeasted breads at first to simplify the timing for they will be much more predictable!

Good Luck!
Jay
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  #12  
Old 12-01-2010, 09:34 AM
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Default Re: Tall fire, yes. Wide fire too.

Hello Jay,
You know, I sort of knew that's what heat loading is. And I don't remember my coming across any mention or discussion on it which might be why I had for a while assumed that getting to pizza hot was enough, and that once that was hit it was ok to stop firing. But logic eventually told me about heat loading without knowing it had a name or that I was even right. And I've only just recently put it together so that and the perimeter fire/hearth heating issues has me feeling better about the next firing/bake (Saturday? Weather permitting).

Your example description of the oven cooling too much and too far and unable to recover in a poorly or insufficiently heat loaded oven makes me ask if you weren't looking over my shoulder recently, like, maybe you were sort of peeking over the neighbor's fence or something. Because you have my experience down almost to a degree. I think I'm gong to print this page and staple it to my forehead till I get this down. Thanks.
Kim
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  #13  
Old 12-01-2010, 12:49 PM
Il Pizzaiolo
 
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Default Re: Tall fire, yes. Wide fire too.

Hi Kim!

More like the voice of experience and recognizing myself and my errors in your description!

I think many of us get infatuated with the get it fired and ready along with a "save the planet and/or our wallet" by not burning extra wood so we creep toward shorter heating periods. And for pizza with a well insulated Pompeii that probably works. My slab is an AS design with 5 inches of cement with insulation below and it takes about an hour and a half to charge it fully for pizza and longer for bread. If I heat for an hour it will slowly cool as I do pizza and I will have to rake coals out and recharge the surface about every half hour if I want really perfect crust. After an hour and a half or so or heating the radiant heat from the dome keeps the hearth hot (so long as I keep flames) and it doesn't ever seem to need recharging.

Your bread looked quite nice. One of my "tricks" to get better crust is to make a batch of ciabatta and bake it with my loaves. I do the ciabatta around 85% hydration and it is wet enough to really add humidity to the oven!

Hang in there. You WILL work out the kinks!

PS: as a stupid example (but I love stupid example) of the importance of heat loading....
Imagine you want to cook a steak. You can heat a cast iron skillet in the WFO to say 600 all the way through and throw a steak on it and it will char the outside of the steak to a beautiful crust. (Might or might not do the other side but...hang with me). I could heat a sheet of aluminum foil to 600 and throw the steak on the foil and it would barely do anything to the steak. The foil would have temperature but not the "heat" storage to heat up the steak. A quick heat versus a thorough one is a bit like aluminum foil versus a cast iron skillet. We have to put the heat into the oven before we can use it!

Keep baking! You are on a good path!
Jay
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  #14  
Old 12-01-2010, 01:33 PM
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Default Re: Tall fire, yes. Wide fire too.

Jay,

Thanks profusely for the words of wisdom and experience. I understand the concept of heat loading (brick-charging?) but had no idea the oven floor could be that dynamic. It now makes a ton of sense that the only way to get to know one's ideal oven equilibrium is through testing. Knowing upfront that soapstone transmits heat at a slightly higher rate than brick (I learned this from IR-ing a sun-baked soapstone slab right next to a firebrick) hopefully means that if I start from a relatively lower temp, I can load my bread, suck out some of the floor heat and utilize the residual heat from the 2.5" of fully-loaded firebricks below while not scorching the bottom of the bread. I'm wondering though, what effect does a higher hydration have on the ability to reduce scorching vs the quality of the bread?

Again, this is one trial-and-error opportunity I am willing to tackle, but have to finish my oven first.

Great analogy with the foil and cast iron skillet. Even I get it!

John
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  #15  
Old 12-01-2010, 03:28 PM
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Default Re: Tall fire, yes. Wide fire too.

Hi John!

The soapstone will not be a problem. You will just wind up with slightly different baking temp/time than if it were refractory. Big deal! (Totally unimportant!)

In my experience dough hydration has no impact on browning or scorching on bread dough that I can attribute to hydration. I can theorize that it might in pizza, but the water content diff of a 200 gram ball of 60 and 70% pizza dough is only 7.35 grams of water (out of about 75 to 80 grams or 10%), (about half a tablespoon!) and that is spread out over about 75 square inches of pizza so there isn't much water diff and the hearth temp can vary a lot so....I think scorching is likely to be more a function of hearth temp than dough hydration. BTW, I used the 200 gram ball just for simplicity of calculations.

Good question! And glad you enjoyed the foil!
Jay
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  #16  
Old 12-02-2010, 08:24 AM
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Default Re: Tall fire, yes. Wide fire too.

John, How is you build going?

Chris
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  #17  
Old 12-02-2010, 03:52 PM
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Default Re: Tall fire, yes. Wide fire too.

Heat loading is a very important concept. If I just get my oven up to 500F and let the fire burn down, not continuing to have a raging fire until the dome clears. The oven will drop back down to 300F in a matter of minutes. The reason is that the total mass of the oven has not reached the 500F temperature. Until the dome clears, you cannot guarantee that the oven is heat saturated. The reason it clears is that all the refractory has come up to passed the flash-point temperature of the soot. Once the oven is heat saturated, the oven will maintain the 500F for hours and is much easier to maintain that temperature with the addition of one or two pieces of wood. The cast iron pan and aluminum foil example is a great one to get the concept of heat loading. But this is a concept the newbie has to understand, or the oven can play games with you. Every oven is different, so you have to get to know your own oven.
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Old 12-02-2010, 05:32 PM
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Default Re: Tall fire, yes. Wide fire too.

This is a brilliant discussion and education. Jay & Iwood are like professors and John & I are students. But with passionate & dedicated professors. If I ever forget to thank you... well, I won't.

Heat loading isn't mentioned much in many of the various bits I've read back at the beginning, when I first started this project. So it did seem that getting the oven up to temp. was enough. But it sure didn't work that way in practice. Yes, my oven temps have dropped rapidly enough so tat once I got the coals out, mopped the floor, closed the door and got the bread ready, the hearth was already too cool to bake. That day was a disaster.

I have been a baker professionally on occasion and I can tell you that all ovens are different and require getting to know them. You develop a bit of a relationship with each one. Bakers especially have to be adept at this whereas meat roasting chefs have less a worry. It's just one reason I love to bake breads.
I cannot thank you two enough for these great descriptions and for just having the knowledge. Tomorrow I am doing some sourdough and some standard French baguettes and I am itching to get at that oven. Aside from the fact that the family is now already into the last loaf of bread in the house (we have not had to buy any in a year!) I almost wouldn't care about baking bread just to play with the fire and oven. except, of course, that baking will help the learning curve. Again, thanks.
Kim
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  #19  
Old 12-02-2010, 06:49 PM
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Default Re: Tall fire, yes. Wide fire too.

How can we know when the oven is fully heat saturated, as opposed to just clear? Is there any set time or formula or something for figuring it out? Or is it trial and error per oven? Once the refractory has cleared there's no next change to look for, so I imagine a sense of timing is all there is. But how does one sort that out? Wait? And wait some more?
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  #20  
Old 12-02-2010, 07:32 PM
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Default Re: Tall fire, yes. Wide fire too.

If you're a professional baker, and you need to get repeatable results, this is the one situation where thermocouples, set halfway into the dome, will give you a reliable read on how much heat is stored in your brick. When the oven first clears the inside of the brick is considerably cooler than the inner face. As you continue to fire the dome approaches (bit doesn't reach) equilibrium. It takes some practice to get it, and you can do it without temperature readings, but it's a little subtle.

I don't do much bread except pitas at blazing heat. The only time I go for a longer firing is for the Thanksgiving turkey, which I didn't do this year.
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