#11  
Old 01-28-2012, 06:38 AM
Il Pizzaiolo
 
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Location: San Antonio
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Default Re: Why does bottom of my bread loaves burn?

From the little you tell us (heating until the dome to 550 or even cleared at 800 or so) the oven is WAY UNDERSATURATED. The norm for bread is to continue firing for at least another hour and half OR THREE. You clearly haven't put enough heat into the refractory - particularly the dome. The temp of your dome is dropping like a rock as the heat flows not into the oven and to the bread but out of the oven toward the insulation. Did you check your dome temp at the end of a bake. It is probably below 300. The top will never turn brown and get crispy in a cold oven. Also...how are you humidifying the oven. That has a major impact on crust.

To your burnt bottoms???? How are you measuring temp. Something is askew. Perhaps your fire building is loading the hearth (but that is not totally credible). Again, as Faith, I think, asked, tell us the formula. Sugar and oil can contribute to burning.

And yes there are subtle differences between hearth baked and pan baked bottom crusts but I don't know how to verbalize them.

There is plenty of good info on baking bread on this website. Follow the proven procedures and experiment with shortcuts after you are having success. Then you can learn. Taking shortcuts before you have success is unlikely to get you very far!

PS: To answer the specific question posed in your Subject line: The temperature of your hearth is too hot for the length of time your dough is on the hearth. As 500 should be a pretty safe temp, I can't tell you why it is "too hot" (bad temp?) or why it needs to be on the hearth so long (more clearly the dome temp is a factor but?), or why your hearth and dome are so far out of balance (inadequate heat loading is probably the cause but there are other considerations that you have not clarified).

Good Luck!
Jay

Last edited by texassourdough; 01-28-2012 at 06:42 AM.
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  #12  
Old 01-28-2012, 10:20 AM
SableSprings's Avatar
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Default Re: Why does bottom of my bread loaves burn?

I agree with Jay on the heat loading of your oven. I found that starting a fire the night before a bake day (usually 20-25 loaves) is helpful when you want a good heat saturation for the oven. I shoot for a dome temp of about 200F at 7 am on bake day. When I use the remaining coals to start the morning fire, I'm not starting with a cold oven and I'm reducing any possible temperature shock on the masonry. Once the fire started in my "warm oven" I've found that having 3-4 hours of dome temp at +600F before baking is essential for deep heat loading. My oven's equalization time will vary between 1-2 hours after the heat loading fires and often times I'm putting in a load of baguettes at 575-590F as the start of my baking (normally around 2 pm).

Something I didn't see in your post was the total time you're baking the loaves. My 13 oz baguettes are done in 18-20 minutes. Also, when I started making bread in the WFO I found that if I moved my loaves around during the bake, they tended to burn on the bottom. My thought is that once you put a dough loaf on the oven floor, it cools that spot a bit. The heat is slowly returned to the contact area of the loaf as the bread bakes and doesn't return to starting hearth temp during the normal loaf bake time...less "excess carmelization" -- so don't move your loaves around in a hot oven during the bake.

Also, as was pointed out, enriched breads (+whole wheat & rye breads) can easily burn in an oven that's too hot...the inverted or double sheet pan trick works pretty well for the bottoms and a piece of foil works for the top.
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  #13  
Old 01-28-2012, 01:21 PM
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Default Re: Why does bottom of my bread loaves burn?

Hi Mike!

You are definitely right about the dough cooling the hearth. I have not seen credible numbers but when you put wet dough at 80 F on hot hearth at say 500 F the dough will both cool and emit steam that will cool the hearth surface to the 212 range. Now, the temp 1/4 inch below will be 500 or so initially (assuming good insulation and loading) and that heat (and deeper) is what flows to the surface to cook the bread. (I know you know that but this is to be more complete for other readers!) When you pull the bread from the oven the hearth will probably be no hotter than 300 to 325.

I am always amazed by the low temp at which many FB people load. I usually load at 565 F on the hearth but my loaves are 1.5 to 2 lb boules and they need a bit more time (so a cooler oven). Your time of 18 -20 minuted for baguettes at 580 or so makes good sense. This spring I need to do a baguette bake. Since I spent a week at SFBI on baguettes I make them great indoors but I have to make them SHORT and it would be wonderful to make some LONG baguettes! Yes! Gotta do that!

Good comments! (Good to know you are in Roseburg. I may have to look you up next time I am in Oregon for steelhead - like this fall!)

Bake On!
Jay
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  #14  
Old 01-28-2012, 09:21 PM
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Default Re: Why does bottom of my bread loaves burn?

You all are firing longer and loading hotter than I typically do. I need to try those. Pulsing, like Mike suggests through multiple fires really heat loads the oven too. I was skeptical about that until I tried it and had my oven stay cooking hot for almost a week.

Outside of firing technique, I've had good luck using brown rice flour under the loaves to prevent burning. I think you told me about that, Jay. I'd also agree with not moving the loaves around.

Bill
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  #15  
Old 01-29-2012, 07:44 AM
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Default Re: Why does bottom of my bread loaves burn?

Wow! Bill! I envy your insulation! WOW! Your big challenge is undoubtedly getting the oven cooled down to baking temps. (It cools pretty fast with the door open but... that that invites problems too). Yeah, brown rice flour will help if your hearth is too hot but...the goal is to have it the right temp!

I would almost bet your hearth is warmer than the dome when you bake - i.e. your hearth mass and insulation may be more efficient than the dome. It is my impression that most ovens have domes at baking conditions that are 20 to 40 F warmer than the hearth (after equalizing). Have you checked yours?

The reason that pulsing works so well is that the preliminary fires warm the deep refractory. As a result it doesn't "drag down" the temp of the surface by sucking heat out of the oven as much.

Thanks!
Jay
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  #16  
Old 01-29-2012, 08:32 AM
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Default Re: Why does bottom of my bread loaves burn?

I don't usually pulse fire. It takes a lot of wood. With a shorter, one time fire (2-3 hrs), it cools quickly. Also, by "cooking temps", I mean further meals, etc, not bread. When I do it, I progress down to slower and slower cooking things, finally ending up with drying of fruits or jerky.

I often do cool with the door off too. Yes, the floor is definitely hotter that the dome, too.
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  #17  
Old 01-29-2012, 10:32 AM
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Default Re: Why does bottom of my bread loaves burn?

Quick question pertaining to this great discussion. What type of oven is everyone using? I would assume the dome style pompeii oven would take less time to saturate than a thicker walled, barrel style which has a much larger thermal mass.

Before interpreting heat times, etc, I want to be sure everyone is talking about the same thing.
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Old 01-29-2012, 11:11 AM
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Default Re: Why does bottom of my bread loaves burn?

Quote:
Originally Posted by mfiore View Post
, barrel style which has a much larger thermal mass.
Not all barrels have masses of mass.
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  #19  
Old 01-29-2012, 01:39 PM
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Default Re: Why does bottom of my bread loaves burn?

My oven's a slightly modified Pompeii (a bit of a teardrop shape - see Dome Build in the photo album link below my signature). The internal width is 39" and the depth is 45" (from door stop to back). I've been baking primarily bread in it since December of 2009 (+1,200 loaves to date).

I've posted this a couple times, but I think it's important for everyone that wants to bake (other than pizza) do some temperature profiles over time to really see the heat loading and thermal properties of their oven - Pompeii or Barrel. Until I actually graphed several firings and their temp profiles, I really didn't have a good understanding of how best to use my particular oven's heating character.

The baguette below was baked at 580F (hearth temp) for 18 minutes. I got excellent spring, just a bit of "extra carmelization" on the bottom, and great crumb. I've included one of my earlier temp profile graphs as well.
Attached Thumbnails
Why does bottom of my bread loaves burn?-dsc06217.jpg   Why does bottom of my bread loaves burn?-dsc06219.jpg   Why does bottom of my bread loaves burn?-dsc06218.jpg   Why does bottom of my bread loaves burn?-dsc06213.jpg   Why does bottom of my bread loaves burn?-tempprofile.jpg  

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Last edited by SableSprings; 01-29-2012 at 01:46 PM.
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  #20  
Old 01-29-2012, 02:44 PM
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Default Re: Why does bottom of my bread loaves burn?

Quote:
a thicker walled, barrel style which has a much larger thermal mass
Hey Mike,

Good to hear from you. How's the oven working? Are you able to use it much in the winter?

I think most of the barrel vaults are built with 4.5" walls and ceilings, same a pompeii like yours, but takes more fuel to heat up because of the vertical corners. I think you'll need to ask one of the builders here who have one of each. Bob maybe? (AZPizzanut)

John
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