The Fresh Loaf

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Do We Really Need Steam?

AsburgerCook's picture
AsburgerCook

Do We Really Need Steam?

I was exploring English Muffin bread, and there seem to be mostly just two recipes "out there." One is the King Arthur version, the other uses an egg. Neither one tastes anything at all like an English Muffin. So I went looking.

I found a recipe for classic English Muffins, which also used (what they called) a biga. To me, it's actually a poolish, but hey...who am I to argue? I made that recipe, and just dumped it into a loaf pan instead of frying them in a pan. (I did a couple of rises to double, but no real shaping -- it wouldn't hold a shape.)

This recipe was so wet, it was extremely hard to work with. It's supposed to be fried, like crumpets, so it's more like a heavy batter. Learning how to work with high-hydration dough, I was able to manipulate the dough. To me, it seemed a lot like ciabatta. But Holy Smokes, did this dough rise!

Long story short, when I finally reworked the recipe, I ended up with a fantastic Italian Sandwich Bread! Seriously good stuff! I suspect the Italians had their bread, and the British came along and fried it.

For about 15 years I've been attempting to replicate a particular type of sub roll. My examples are from Turano or Gonella in the Chicago area. Another example is Amarosa out of Philadelphia. And there's a place in New Orleans that sounds similar. It's been impossible. There's a recipe here on Fresh Loaf I was about to try, when this astonishing miracle of serendipity happened.

I'm now making the 8" rolls, and will also add in whey. With just plain water the bread was superb (I'll do a recipe later), but the rolls have slightly too much crust. Obviously: Steam!

Have you ever put a pan of water in the oven and watched it boil? Like when you're braising a casserole or meat/poultry? The water's happily boiling, but...there's no steam! Why not?

Check this out from a thread on the physics and thermodynamics of steam and vapor:

Steam in general refers to the gas phase of water. Steam can be the same as water vapour in some contexts. In more casual usage, steam can refer to the mixture of vapour and aerosol liquid water droplets suspended in the vapour. The "steam" you see rising off boiling water for example, is the second type. What you see is actually condensed liquid water; as water vapour itself is not visible to the naked eye.

I tried several mechanisms to get steam, and came to understand why surface area matters. However, I got curious and put a plain pan of water in the oven at 350F. No steam. Then I put a Pyrex pie plate in the same oven and before I even could set down the pan on the rack, it clouded up with "fog." That's the same as steam, I believe.

Why do we want steam at all? Most here know it's because it retards the formation of the outer crust, keeping it soft so the inside of the bread can continue to expand. We want the "skin" of the loaf to stay somewhat cool until the loaf has risen all the way. Then, remove the steam and allow the final browning.

Hmm. So what's actually cooling that "skin?" Isn't it the water, at just over 212F, being cooler than the surrounding hot air (at 350F)? In fact, isn't the reason I got instant fog on my glass plate is because I was putting a room-temperature surface into a super hot atmosphere filled with.....water! As vapor!

The loaf going into the oven is, what...around 80F or thereabouts? Somewhere around room temperature. Ordinarily, the humidity in the preheated oven is extremely low. "Ovens are designed to remove humidity to promote even baking. A 350-degree oven has a relative humidity approaching zero." - AI

The small amount of water in the outer skin will boil off quickly in the hot oven, leaving the flour (and possible fat) to start burning: the browning. Adding continual water will prevent the flour from drying out and burning. Ergo, steam provides a source of water. The steam doesn't matter. We perspire when we're hot because the heated "water" of the perspiration evaporates. The exchange of energy removed heat from the body. But the surface of a loaf of dough has no way to "perspire" or sweat. :-) Gotta spray it with water, like keeping a cat cool.

If I put a wide pan with some boiling water into the oven, it can sit while I'm preheating or for some time. It will continue to emit water vapor, since a) it was 212F when I put it in, and b) the oven is well above 212F. Ergo, there is constant water vapor in the oven "air."

When I then put in an 80-F piece of dough, it will immediately develop condensation on the surface -- the "skin." Right? The exchange of energy between that condensation, its evaporation, and the gradual increase in temperature of the dough "should" produce the same effect as steam. Right?

I shouldn't need to actually see billowing clouds of white steam. Those clouds are really only the water vapor condensing rapidly in the hot air. It may deposit on the dough, or maybe all over the oven, but it's no different than actual fog or morning mist over a river. 

Seems like it, anyway. So I'm going to try for my thin crust with just a 10x13" roasting pan and about 1-2 inches of boiling water....just sitting there. It's a lot easier (and safer) than throwing water into a pan that's already hot. And less cumbersome, and I don't need lava rocks, towels, or anything else. Just boiling water. :-) We'll see.

Side note: I tried the steaming cotton towels rolled and put in the preheated oven. It sort of works, but the bottom of the towels remained wet, while the upper parts dried out fairly soon. Surface area exposed to hot air. The towels may have a lot of water, but it doesn't "wick" to the upper surface quickly enough to compensate for evaporation.

squattercity's picture
squattercity

I suspect you are right, Asburger. Huge vapor clouds -- and the accompanying sizzle from throwing ice cubes into a super-heated cast iron pan -- are for show. To tell our disbelieving brains: look! steam!

Rob

tpassin's picture
tpassin

A very long time ago when I worked in a Physics lab, we had to take a large piece of stainless steel, with a complex shape, to be vapor degreased.  Back then it was common to use trichloroethylene for this purpose.  It's a clear, but volatile liquid at room temperature and turns into a heavier-than-air gas at moderate temperatures, about 190 deg F.  At the cleaning facility there was an enormous tub without a cover. There was hot vapor in the tub - you could make out a slight foglike effect but it was clear above.

Our part was lowered slowly into the tub by a hoist above it.  When the piece sank below the top of the tub, clear liquid suddenly appeared like magic and flowed all over our part.  That was the condensed  trich doing its cleaning job.  It was a very dramatic sight that I remember these more than 50 years later. After some minutes, our part heated up to the vaporization temperature and liquid stopped condensing on it.  The job was done.

This is beyond doubt what happens with a loaf of bread-to-be as well. What AsburgerCook has written is no doubt correct.  There are a few other points to think about, though. One is that water condensing on the surface of the bread releases much of its heat of vaporization to the surface of the bread, and that's a lot of heat. So the surface of the bread can heat up quickly somewhere between the dough temperature and the boiling point of water.  It can produce a gell-like effect, and that gell-like skin will stay moist for some time. This is the origin of the sheen that I get on many of my loaves. This effect reduces the drying and burning effect of the hot oven air for some time, and also should help the loaf to expand.

During this time, a baking steel or stone if used keeps pumping a lot of heat into the bottom of the loaf, promoting good rising.

Another thing to consider is that ovens, whether by design or accidents of construction, don't hold water vapor in very well, and many ovens can be damaged by too much water vapor - mostly the newer electronic controls, I think.  Of course they have to be able to withstand some moisture because many foods will give off a lot.  If you start off with a lot of water, even during preheat, the moisture will be in the oven that much longer than if you throw in the water later when you put the loaves in.  I don't know how to balance this out, but it must be a factor in play.

Another difference between putting water in during preheat and throwing it in later (and producing clouds of steam) is that throwing it in later will drastically lower the oven temperature for quite some time. The details will depend in the oven design, the location of the steam generating apparatus, the size and location of the baking steel, and so on.  I routinely see the temperature above the steam pan go down below 300 deg F and stay down for a long time.  The air above the bread stays cool for a long time, too. 

Because of this, the effective temperature that bakes the loaf during the first part of the bake cycle is much lower than the oven temperature setting and much lower than you think.  Our home ovens take a long time to recover their temperature.  I have proved this by turning by oven setting down to 300 deg F or even 250 right after throwing in the water to make steam. The bread baked the same way as if the temperature setting and been kept high the whole time.  Now I routinely turn it down to 300 or 350 deg for 12 or even 20 minutes before returning the setting to 415 of 425 deg F.  The bread may even bake more quickly (hard to be sure), than with the setting kept high, and it's certainly baked at least as well and, it seems to me, more consistently and with less tendency to burn the crust.

You want to find a balance between creating high humidity during the first part of the bake, and allowing the bread to dry out better during the latter part.  If you start heating the oven with some amount of water, it may or may not still be there generating its water vapor by bake's end.  I know that when I throw in my 12 oz of tap water into the steam pan with its rocks, the pan will be dry before the end of the bake.  BTW, I used to boil the water before throwing it in, but when I tried not pre-heating the water it didn't change how the bread baked. So now I don't preheat the water.  I also tried adding more water to the steam pan after say 5 minutes.  That didn't generate another visible cloud of steam/water vapor, it left some unevaporated water in the pan, and didn't change the baked results so far as I could see.

I should probably try preheating the oven with water in the steam pan.  I've toyed with the thought but haven't actually done it.  One thing I'm sure about is that I will not be removing the steam apparatus in the middle of the bake as some people do. That's just asking for serious burns and scalds if something goes wrong.

TomP

AsburgerCook's picture
AsburgerCook

Dayum, there's a lot of good stuff here! I was just thinking about having the effect of steam without freaking out about the billowing clouds. I hadn't really contemplated that people are already doing this! LOL! It reminds me of that Helen Rennie who has a brainstorm, figuring it's new, then goes out and looks around. Only to find that no, it's not all that new. :-)

Okay: My understanding of the baguette thin crust is that there's about 15 minutes of steam at the start of the bake. Then the water/steam is removed for the remaining (whatever...20mins or something) time. You sound as though you're specifying steam for the entire bake time?

I've used a foil tent over damp dough in a hot oven, then removed the foil after 10+ minutes, which I now know is using internal moisture from the bread and capturing the vapor. I've got a couple of King Arthur recipes that also start with a tent, then remove it. I think I'm now understanding the "why" of that.

So I believe?...that this "gel" you're referring to is what I want, right? It's starches? Is that gel the basis for what eventually becomes the crust? What makes the gel thick, for the artisan crust, versus very thin and shattering? Is it the time involved with the water moisture?

I have a basic home electric oven (GE), with nothing fancy other than self-cleaning. I hadn't even thought about the reduction in temperature from the water, and that totally makes sense. It's why I figured I'd have the boiling water go in during the preheat. 

The water -- maybe 1-2 inches in a 10x13" steel roasting pan -- would be at 212 minus temperature loss when I pour it in from the kettle. That goes into a pre-heating oven, and I'm "assuming" that the oven thermostat will simply read the air temperature.

Therefore; the combined effect of the heating element and the added water and steel pan will make a cumulative average. So when the oven Pre-Heat beep goes off, that means the air temp in the oven has reached my baking temp. Let's say 350F. As such, the water will have reached 212 and the oven air is 350. (Interesting to put a heat proof hydrometer in there! Probably melt at >300 though.)

I've done a lot of braising in this oven, so I'm not worried about moisture escaping to possibly impact the controls. There's a single vent under a back burner, but overall the oven holds a good temperature. I should likely use an oven thermometer for a better reading. I hadn't even thought about the drop of 50-degrees, which then stays there regardless of what the oven has to say about it.

I think -- not sure yet -- that these Italian rolls are going to work at 350 rather than a more typical 450. This is a big experiment based on a completely accidental result from changing the English Muffin recipe. I know what I want, but have spent probably 20 years trying to replicate it. Haven't until now, so there's time for experiments.

The oven will have to keep the water at boiling temp. I foresee perhaps about 10-15 minutes of vapor, so I'm guessing I'll have about 260 cubic inches of water available. I doubt all that water will vaporize in the 15 minutes, wouldn't you agree?

Interestingly; when I used the rolled cotton towels, the bottom was wet and the tops were completely dry -- that wick effect I mentioned. With just plain water sloshing around (who knows, could have an earthquake), as the upper layer vaporizes, the lower layers should.... climb and encounter the hot air? Like turnover in a lake?

Therefore, it sounds like my main variable is going to be an accurate 350 degrees. And even there, I'm fascinated that you didn't experience a difference baking between the 300 and 350 or whatever your start point was. I've "kind of" noticed that, but figured it was more about a) how quickly will the bread finish baking, and b) how dark will the crust eventually become.

I'm making a faux croissant with egg wash, and when I baked at 350, I got a light golden crust in 11 minutes. Raising to 375, got a better crust color. Then I saw a hack to start at 400 for 10 minutes, then drop to 350 for around 10 minutes, and that was excellent. So it seemed like the temperature was affecting only the Maillard reaction AFTER the flour had dried out.

I also know that it takes a long time for a pie to brown because as the crust and filling are climbing up to 212, it all plateaus when the water is in the process of vaporizing. Then, like a rice cooker, after the water is "gone" for the most part, the crust browns. 

Ergo, the bread crust should be similar, right? Totally cool description of what you've already found -- I think this is going to work! If so, I'll write out the recipe. :-)

Added note: Removing the water part way through the process won't be a problem. I move pans in and out of the oven all the time, with various amounts of liquid sloshing around. This is a turkey-roasting pan, after all, and kind of designed to be handled in such a way. Plus, I see no reason why I can't put the water on the same oven rack as the bread. A second, lower rack could actually increase the possibility of an accident.

tpassin's picture
tpassin

So when the oven Pre-Heat beep goes off, that means the air temp in the oven has reached my baking temp. Let's say 350F. As such, the water will have reached 212 and the oven air is 350. (Interesting to put a heat proof hydrometer in there! Probably melt at >300 though.)

It's not as simple as that. The air in the oven will not be at the same temperature all over.  The air near the water source will be cool and there will be temperature gradients all over the oven.  The longer the oven gets preheated, the more heat will get stored in the oven structural material and the more constant it will manage to hold its temperature.

On top of that, the oven thinks that its "temperature" is whatever the oven's temperature sensor sees at its location. It won't necessarily even be an average of the temperature throughout the oven. Also the temperature gradients will change when the heating element comes on. The idea that a home oven has "a" temperature everywhere during baking a loaf of bread can be far from the truth. It's too complicated to sort through with any accuracy, so in the end - as always - you have to proceed empirically, guided by the generalities.

As to a thin crust, I don't know for sure but I think the a high temperature at the crust must play a big role.  Think about what happens at the loaf's surface.  Heat transfers from the oven air but slowly. Steam in the oven will transfer heat much faster since the water will condense and hive up its heat of vaporization.  The surface will absorb water and start to gell, but the interior will be slower to heat up.

The surface has to dry out before its temperature can rise high enough to dry out brown and brown.  If this happens slowly there will be a thicker region near the outside that can dry out and cook this way.  If the temperature gradient through the surface is high, that's when a thin layer of the crust can dry out and brown before the rest of the loaf gets cooked. To get a high temperature gradient you need need a very hot oven.

AsburgerCook's picture
AsburgerCook

From what I've read about the process of forming a crust, there's that "skin" we've mentioned before, which is formed over (around) the risen dough. It's not too thick, but simply air-dried dough. And it's a function of letting dough rise, whether in the pan or whatever final rise. 

That skin is what gets cut when scoring the dough. If it's left intact, it provides some nominal resistance to the expansion of the dough. By slicing (venting), it allows a) the inner moisture to heat and rise, pushing up the bread (oven spring), and b) the surface to move, pulling apart to allow room for the inside dough to expand. Minus the scoring, the bread doesn't rise as well during the bake.

Essentially, if I understand it in this context, the overall temperature of the dough, as well as its moisture content will be one thing. But the moisture content (and presumably temperature) of that surface "skin" will be quite different. With a lot less moisture, it'll heat up a whole lot more quickly than the inside of the dough. Much like we wear a coat to manage the cold air temperature, while keeping a warm body temperature.

The surface of a winter parka will quickly become very cold when it encounters sub-freezing air temperatures. But it will take a long time for our actual skin to also arrive at the freezing temperature. Since we can generate our own heat, we typically don't freeze. If we're dead, and can't generate the heat, then it still will take a longer time for the body to freeze (not rigor mortis) than for the surface of the parka to equalize with the air. Right?

How quickly or slowly the surface "freezes" in place is where steam enters the chat. The "skin" already is a lot drier than the internal dough, so it will quickly start to burn -- the start of browning. It forms a somewhat firm "dome" over the dough, trapping gas and steam underneath. 

That internal moisture has nowhere to go, so it begins to accumulate under the surface of this new "dome." With the surface getting hotter and hotter, the moisture below that "skin" also begins to evaporate, or to be absorbed into the underside of the "dome" surface, building a thickening layer.

As time passes, and the process repeats, the eventual crust becomes thicker and thicker. 

So the main problem is to keep the surface of the dough at the start of the bake flexible, soft, and expandable -- closer to the inside temperature and moisture of the overall dough. Some of that's done by the scoring. But a lot is done by cooling down the surface.

I believe what we're talking about in this thread is the physics of how that cooling takes place. What worries me a bit, is your point about that "gel." I get what you're saying, but it's new information for me. It isn't part of how I was (vaguely) understanding crust formation.

I also totally understand your points about the dynamic shifts of the inside oven air. Especially the one about how the air above the water surface will be cooler, due to the energy exchange. Hadn't thought of that at all! Hmm... so put the water surface below the bread, on a lower, second rack, or next to the dough. Not sure yet.

I also understand the concepts of temperature "spots" throughout the oven. Okay, and that's fine: The bread I've made so far is pretty consistent from front to back, left to right. I'm sure there are these hot spots, and cool spots, but I'm wondering whether they'll be amplified by this introduction of humidity.

Re-reading your comment, I wonder if we're talking about the same thing, but seeing it from two different directions? I'm seeing the outer surface of the dough changing quickly (without steam), due to a head start of being fairly dry. The inside surface -- the overall dough -- is a lot cooler, and more moist and heats up slowly.

You seem to be indicating that the outer surface -- the "air-facing surface" -- would become... cooler than the inner dough? Due to the rapid energy exchanges taking place via the moisture?

tpassin's picture
tpassin

Skin: A dried skin is not what holds the shaped loaf together. Surface tension is the main agent.  A water balloon is not a bad model.  The higher the curvature (therefore the smaller the loaf) the stronger those forces are and the smaller are the forces from gravity pulling on the contents. A small water balloon forms a tight little ball, a large water balloon forms a big floppy bag.

Most of my loaves do not have a dried skin at bake time.  I proof them covered and they don't dry out much.  In fact, sometimes I uncover them for the last 15 minutes of proofing to dry it a little because that makes scoring easier.  It doesn't make much if any difference in the expansion of the loaf.

Gell: When I generate great billows of steam (yes, I know that the visible part is condensed water vapor, not actually steam), right after putting my loaves into the oven, very quickly the surface becomes wet and glistening.  That's the water that immediately condensed onto the surface. When starch in the presence of water reaches a certain temperature it turns into a gell. The starch in the dough is mixed with water so the starch near the surface will start to gell and hold onto its water.  The condensed water on the surface adds to the thermal mass that must be heated up by the oven so it slows down the heating of the crust.  That surface water also has to evaporate before the surface can heat up above the boiling point.

As the surface is going through this process, it is transmitting heat into the interior but not too quickly since the temperature differential between surface and interior is relatively small. The baking stone or steel (or Dutch oven) is busy conducting a lot more heat into the bottom of the bread because the temperature differential at the bottom of the loaf is much higher, and especially if the base is metal, it contains and can conduct a lot of heat.

As the interior of the loaf heats up it too will get hot enough to gell. It may even develop circulation currents inside. Gravity tries to make the loaf slump and bulge, and the surface tension in the skin resists this.  If you doubt this, bake a loaf and after it has mostly risen but is still very delicate, cut or tear the skin on the side of the loaf.  You will see the interior dough start to ooze out at the tear. This has happened to me by mistake (I won't get into how it happened).

Steam: DocDough (linked in another thread) showed by experiment that the expansion of unscored loaves with steam is barely more than the expansion without steam. However, I'm not sure how definitive that experiment was because 1) it was for demi-baguettes and being small in diameter, their shape is dominated by surface tension and not so much by gravity.  A larger loaf might show a different result. 2) I don't know how much steam he generated relative to my practice.

When I bake a loaf with high humidity in the oven (because I put water into the water pan during preheat), I tend to get a dull, grayish-brown hard crust.  When I create great billowing clouds of steam by throwing water into my water pan right after the bread goes in, I tend to get a thin, crackly, reddish-brown crust with a sheen.  Sometimes they even look lacquered. The difference in color must be because of chemical reactions that take place in the presence of all that water that don't without it, but I don't know what they are.  As the bake progresses, that shininess of the surface slowly decreases but normally some or much is left when the bake is done.

AsburgerCook's picture
AsburgerCook

Tom; you and Rene and everyone else on this post have got me seeing crusts entirely opposite from what I'd thought. I'm the one who's upside down on what's happening. Intuitively, I'd thought of bread as me being hot in the summer and using a sprinkler. I should have been thinking of being cold in the winter and taking a hot shower.

The sprinkler is cold water on hot skin, while the shower is hot water on cold skin. I warm up a lot faster in the shower than I cool down under the sprinkler. Goes to show you how mental images can lead to messed up thinking.

I should also say that "skin" and air drying isn't because of uncovered rising. I do cover the dough, sometimes in oiled plastic, or other times in a rising bin. But regardless of how the dough rises or proofs, there's going to be a thin membrane (also a good word) at the surface. It's not particularly a bag holding the bread together, but just a "skin." And it's the right thickness that I'd like to keep it that thin instead of "growing" into a thicker crust. See?

Here's what I want to accomplish. There's a unique bread roll that I've found in only three examples: Turano and Gonella, two bakeries up in Chicago, and Amorosa out of Philly (although they've moved to NJ). The Turano French Roll is an excellent example, for the purposes of this thread.

Turano French Roll Web Image

The Fresh Loaf forum post I'd found and was going to try (until this current serendipity) has the same problem as everyone else in trying to describe the bread. 

Real Italian Hoagie Rolls | The Fresh Loaf

These rolls have certain characteristics. 1) When you take one out of the plastic bag of six, it feels extremely light. 2) Each roll, and some of their other breads feels almost stale. It's quite dry to the touch, but inside there's some moisture -- like typical Italian bread. They're not really made to be eaten cold, right from the bag.

3) It has a very light, almost yellowish crust as if it hadn't baked long enough. 4) There's a longitudinal score that almost has disappeared into the bread. 5) The crumb is very open, often with large bubbles. Some rolls have such a large bubble it interferes with making a sandwich. The ingredients list shows they use whey, which makes sense.

Here's the thing: When you loosely cover a roll in foil and re-heat at about 350F for maybe 5 minutes, you suddenly get a "fresh baked" roll that's moist, nicely chewy, and has a crust that bends a little, crackles, then shatters. There aren't many crumbs when eating the roll, but what there are tend to be "flakes" of crust.

The bread (and company) make the iconic Chicago Italian Beef, often found at Portillo's restaurants, the legend that it is. So too, the Amorosa roll makes the Philly Cheesesteak sandwich legendary. If not for the bread, the sandwiches would be "normal" and average.

The Italian loaf bread I accidentally created uses the five sides of a Chicago Steel pan to bake nicely. That crust is fairly thin, crispy, and easy to chew. It's not an artisan bread, and not a standalone Italian bread crust, which is quite thick and something I can't eat (with my old teeth). This loaf is more like the original baguettes I remember from when I was a kid in France.

I'd thought, until now on this thread, I could just make the dough into four 8" rolls, put them in a silicone "mini baguette" mold and bake them the same way. Nope! 

I now understand that the loaf pan is capturing a tone of heat in the metal, whereas the silicone mold relies entirely on radiant heat and air temperature as it impacts the surface of the dough.

I'd thought I could keep the 350F I baked the loaf bread with. But I'm worried about the "grayish" crust, so now I'm thinking 450F. But what about "steam?" Hence this thread.

I understand that the outer membrane (skin) on the dough isn't holding together the loaf. But I'd thought it was strong enough that as it "set" in the heat, it could prevent free expansion of the underlying dough. Okay, not true.

I think I'm learning that what I may want is to "cauterize" that membrane, almost like frying it? Yes, it might have bubbles or even blowouts, but wouldn't it keep that super-thin measure? 

And how come you get different results from the vapor in a pre-heated oven, from when you suddenly introduce steam when you put in the dough? Is that the gelatinization due to...what... more water already in the air?

The hardest part of all this (over 20 years) has been the super light loaf. I accidentally arrived at that ultra-light weight when I drastically increased the hydration, and did three rises with the first two going to triple in bulk. Surprisingly, the bread didn't deflate! It wasn't delicate, and when I did the last rise in the loaf pan, continued to rise until 1-inch above the rim.

When I took the loaf out of the pan, it was radically lighter than anything I've baked before. It had a pretty open crumb, too, just not as open as free-standing rolls. It reminds me of ciabatta, with how slack is the dough, and somewhat difficult to work with.

And yet, when I tasted this bread it was fantastic! I had an end slice, and did some work around the kitchen. But half an hour later, I was still thinking how good the bread was, and got the "I think I'll have another slice" success. :-)

Now all I have to do is turn the loaf into (apparently) 5" rolls. My mold has 8" slots, and I figured I'd maybe cut the longer rolls in half. But I did find a different mold with shorter rolls.

 

tpassin's picture
tpassin

So when the oven Pre-Heat beep goes off, that means the air temp in the oven has reached my baking temp. Let's say 350F. As such, the water will have reached 212 and the oven air is 350. (Interesting to put a heat proof hydrometer in there! Probably melt at >300 though.)

It's not as simple as that. The air in the oven will not be at the same temperature all over.  The air near the water source will be cool and there will be temperature gradients all over the oven.  The longer the oven gets preheated, the more heat will get stored in the oven structural material and the more constant it will manage to hold its temperature.

On top of that, the oven thinks that its "temperature" is whatever the oven's temperature sensor sees at its location. It won't necessarily even be an average of the temperature throughout the oven. Also the temperature gradients will change when the heating element comes on. The idea that a home oven has "a" temperature everywhere during baking a loaf of bread can be far from the truth. It's too complicated to sort through with any accuracy, so in the end - as always - you have to proceed empirically, guided by the generalities.

As to a thin crust, I don't know for sure but I think the a high temperature at the crust must play a big role.  Think about what happens at the loaf's surface.  Heat transfers from the oven air but slowly. Steam in the oven will transfer heat much faster since the water will condense and hive up its heat of vaporization.  The surface will absorb water and start to gell, but the interior will be slower to heat up.

The surface has to dry out before its temperature can rise high enough to dry out brown and brown.  If this happens slowly there will be a thicker region near the outside that can dry out and cook this way.  If the temperature gradient through the surface is high, that's when a thin layer of the crust can dry out and brown before the rest of the loaf gets cooked. To get a high temperature gradient you need need a very hot oven.

squattercity's picture
squattercity

TomP & Asb -- I wonder if my experience baking with an Anova oven might add something to this steamy tale.

The Anova has a steam function you can set. When it is steaming, it releases a trickle of white vapor at the bottom of the box outside the oven -- seemingly where the element that heats the water is -- but inside the box the air never visibly changes. Also, it has a super-responsive digital temperature read-out and the oven temp doesn't seem to waver due to the steam injection -- though it falls dramatically (perhaps 50 C or more, in my memory) when you open the door and load the bread and takes close to a minute to bottom out and another 2 or 3 minutes to rise back to the temperature you had set.

What's more, since the Anova has a giant window and good quality interior light, you can watch the bread rise. That's how I discovered that, contrary to my expectation (and contrary to my later experience with a dutch oven), the rise does not cease when the steam ends and the crust supposedly hardens. Rather, it keeps going all through the bake. For many of my breads, the final, Eiger-like peak (sorry, I was using the oven at my brother-in-law's apartment in Switzerland) didn't pop into place until about a minute before the bread was done.

Rob

tpassin's picture
tpassin

That's very interesting.  Thanks, Rob.  I keep toying with the idea of getting an Anova but not so far.

In my oven, most of the rising occurs in the first five or so minutes. I don't see much after that. The door is too hazy to be able to really see through so I am going by quick peeks.  I'm sure that's why I don't often get really open crumb.  Well, it can be very open, just not with large, irregular holes.  I've gotten some great, thin, shattering crusts, though.

AsburgerCook's picture
AsburgerCook

Setting aside that I don't have something like the Anova oven, I'm fascinated to hear that the temperature doesn't change all that much with the injection of the steam. But it DOES change radically, with just a simple opening of the door. 

I'm also interested in the recovery from the small drop with the steam injection, and now I'm wondering: Could you do an experiment and have the oven at some temperature, without injecting steam. Then open the door long enough to mimic putting in some bread, and close the door. 

About how far does the temperature drop, and then about how long before it comes back up to the original?

I know: This wouldn't really be too similar to an inexpensive home oven, but this "drop and recover" point is something I'd never even contemplated adding into the process. I know I'm not supposed to open the oven door while a cake is baking, because my mom told me not to. :-) No science, just my mom. LOL!

Seriously: I understand an oven temperature can change quickly with simply opening and closing the door. But until your comment, had no real way of knowing much about how to compensate for that. I mean; we have to open the door to put in the bread, right?

Hmm... maybe we could use a Star Trek Transporter to simply beam the bread into the pre-heated oven. Or... maybe not. :-)

tpassin's picture
tpassin

Setting aside that I don't have something like the Anova oven, I'm fascinated to hear that the temperature doesn't change all that much with the injection of the steam. But it DOES change radically, with just a simple opening of the door.

I don't think this is an important factor, at least not for a home oven, because when the oven has been well preheated it will recover its temperature decently, and in the meantime the thermal mass of the loaf prevents it from changing temperature much while the door is open. The Anova will have a lower thermal mass so it might be affected more.

AsburgerCook's picture
AsburgerCook

I have this bread I'm working on that needs three rises, and it's finally turning a bit cold, here in North Carolina. So I put the dough in the rising bin, and have been using the oven with the oven light method.

With this discussion, and the data from the Anova, I got out my wired digital probe meat thermometer. I've checked that in the past, and it's very accurate -- to 1 degree, basically. I rigged a way to have the probe standing up on the rack, with the sensor tip at about the same level as the middle of the oven -- about where a loaf surface would be, and where the rising dough level sits.

I was shocked! Apparently a bit ignorantly, I turned the pre-heat (350F) on for about 10 seconds, just to get the inside of the oven above 75 degrees, the ambient air temperature. I've put dough in a cold oven with just the light, but the dough sucks up the heat from the light (I think 40Watt appliance bulb), and is very reluctant to rise.

Anyway: I only gave it 10 seconds (by count), then turned it off. Naturally, the electrical "inertia" or overrun, or whatever word, kept the element going a bit. Pretty soon, the temperature in the oven was 106F, way too high (in my opinion) for dough rising.

Fine: So I opened the oven door a "crack," which is about 6-inches to the first stop. It took maybe 10 minutes! for the oven to slowly get back down to 85F. I closed the door, having put in the dough bin. Light was Off. About 5 minutes later I checked, and the temp was back up around 97F degrees!

Dayum! Lesson 1: Press the pre-heat, count to 2, turn it off. Lesson 2: Use the probe when rising dough! 

Okay, so I kept the oven about 87F by turning on or off the light, opening or closing the door, and allowing the dough to generate some heat from its own rising. Not a big problem, but I was thinking about that "recovery" time.

Next thing was to bake the bread (later in the day, after all rises). It's going 350F for 20 minutes, in a silicone form, and should get to around 190-205F. I pre-heated the oven to 350F, let it sit about 5-10 minutes, then put in the bread. 

Everything was fine for about 10 minutes, but then I checked, and the oven was now at 385F! I figured it's been doing that and I just didn't know, but the bread comes out fine. Probably because it's cooking a lot hotter than I would have thought!

I left it for the 20 minutes, then opened the door, removed the bread, and closed the oven door again. I left the oven running, while I checked the bread temp (it was done). Then I looked, and the temp was "crashing!"

Within a minute or so, the oven went from around 380F to 325F. And keep in mind, I'd only opened the door to remove the bread -- what...30 seconds? But without the hot bread, and the door change, look at how much the air temp went down! On its own, because the door was closed!

Out of curiosity, I watched the temp go down, down, down, until it bottomed at about 320F. It then started climbing back up, slowly.

I thought about Tom and Rene explaining radiant energy, and apparently that's what was coming from the sides of the oven. Just FYI: It took about 4 hours for the temp to eventually end up at 145F, and I went off to bed. I don't know how long it took to get back to 70-degrees, but when I woke up the next day, I checked. That's what the air inside the oven registered.

Amazing!

Davey1's picture
Davey1

No. Enjoy!

ReneR's picture
ReneR

Interesting discussion. I have a new oblong Dutch oven, that is bigger but also slightly lighter than my previous round one and seals more hermetically than the old one. I'm still figuring out how to bake with it because, even with my most consistent loaves, the bread is not coming out like with the previous one. Too much oven spring twice, darker crust twice, and too thick crust once after reducing oven temp by about 10C. 

Made me realise how even tiny changes to the baking environment can have significant impact on the final result. More than maybe we realise.

This past thread might help shed some light on this discussion.

tpassin's picture
tpassin

Thanks. ReneR, Doc's post was really interesting.  It aligns very well with my thinking except I never worked through the numbers. One difference is that I have always assumed that radiant energy from the oven walls played a small part at our temperatures.  If Doc got the numbers right, that's only partly the case.

BTW, the reason the term (T1^4 - T2^4) is not the 4th power of the temperature difference, i.e., (T1 - T2)^4, is that T1^4 is the radiant power emitted by the the oven structure and T2^4 is the radiant power emitted by the loaf. The net power input is the difference of the two.

Doc wrote a cogent saying in a related thread:

 I learned about 25 yrs ago that unless there was an experiment that I could perform to demonstrate that something was true, I need to reject non-academic pronouncements about the underlying phenomenology.

"reject" might be a little strong, but "be very skeptical about" fits the bill for sure.

ReneR's picture
ReneR

I'm all for empiricism, but we still have to make bread where there are a lot of things we cannot measure (see LAB vs yeast debates, for another example). So we are constrained to wander into the realm of what I have heard being referred to as 'qualculation' and trial and error, which are acceptable heuristics I think for what we do (and maybe add to the fun of it?!).

Having said that, I always thought that radiant energy might have more of a role than assumed in the case of ovens, as trapping radiant energy is an important part of what ovens are supposed to do. 

tpassin's picture
tpassin

... as trapping radiant energy is an important part of what ovens are supposed to do

Where did that come from?  I've never seen it suggested. An oven needs to be well insulated for both safety and efficiency, and unless its walls are somewhat transparent in the infrared range an oven isn't going to leak much radiant energy whether that was intended or not.

If radiant energy played a large role in normal cooking (except for a broiler element), then a convection fan would have much less effect (since it would increase. a smaller fraction of the cooking ability). DocDough estimated 20%. If so, that's not large but not negligible either.

ReneR's picture
ReneR

Seeing the bricks on the floor of a wood-fired oven turn white around the focal point of the dome of the oven with a relatively small amount of burning wood, I would say it is an important part of what ovens do. 

I seem to also remember my A-Level physics textbook with a diagram of an oven and the rays bouncing around the walls inside. But yes, for a home oven it is not going to be as important. 

ReneR's picture
ReneR

Tom, I have some fun reading for you and anyone who fancies a little physics here.

An academic friend who is a physicist and having lived in Italy loves good pizza and makes it very well at home in a home oven pointed me to a paper about the physics of pizza making.

Here is an extract from the section about radiant heat:

 

Thermal radiation

To answer this question, we first need to consider the second important mechanism of heat transfer: thermal radiation . Its intensity, the amount of radiation energy arriving each second to 1 cm^2 of surface in the oven, is determined by the Stefan–Boltzmann law:

I = σT^4, (10)

where σ = 5.67 · 10^−8 W · (m^2 · K^4)^−1 is the so-called Stefan–Boltzmann constant. A typical brick oven has a double-crown vault filled with sand, which is kept at almost constant temperature. Its walls as well as the bottom part, are also heated to Two_1 = 330 °C = 603 K, meaning that the complete volume of the oven is ‘filled’ by infrared radiation. With a temperature that high, this radiation becomes significant: a pizza in this oven is continuously ‘irradiated’ from both sides by a ‘flow’ of infrared radiation of intensity

I_wo = σ(Two_1)^4 = 5.67 · 10^−8 (603)^4 = 7.5 kW · m^−2, i.e. each second an amount of energy close to 0.75 J arrives at 1 cm^2 of pizza. Here one should notice, that, in its turn, the pizza also irradiates out a ‘flow’ of the intensity I_pizza = σ(T_pizza)^4. Since the major part of the baking time is required for the evaporation of water contained in the dough and toppings, we can assume T_pizza = 100 °C = 373 K, since the toppings will boil at this temperature till they (and the whole pizza) are well cooked, which results in a radiation intensity of I_pizza = 1.1 kW · m^−2, i.e. 15% of the obtained radiation, the pizza ‘returns’ back to the oven. For the much less heated electric oven, the corresponding amount of energy, incident to 1 cm^2 of pizza surface, is less than half:

I_eo = σ(T_eo_1)^4 = 5.67 · 10^−8 (503)^4 W · m^−2 = 3.6 kW · m^−2, while the returned radiation is the same: 1.1 kW · m^−2.

It turns out that in WFOs, as there is very little convection from the burning wood, the baking takes place from conduction from the floor (at a slower rate) and radiation from the dome (faster rate) and the pizza in effect bakes more from the top down than the bottom up.

According to my friend, even in a home oven with the convection fan on, as the oven heats with the hot air the walls will start to radiate energy so, even in that case, where convection is the primary mechanism, radiant heat is still important once the oven has been pre-heated and the fan is as much on as off according to the thermostat.

Here is the full citation and link:

Varlamov, A., Glatz, A., & Grasso, S. (2018). The physics of baking good pizza. Physics Education, 53(6)

tpassin's picture
tpassin

Now that's fun. In an very hot (think, say, orange hot) oven where the interior is in temperature equilibrium every where (sometime called a hohlraum), if you were to peer into a porthole you wouldn't be able to see any structure in the oven.  No walls, no racks, nothing but that orange glow.  That's because all parts are emitting the same intensity of radiant light energy, so there is no contrast.

The same would be true in a cooking oven, only in infrared which we can't see, if it were in thermal equilibrium. I doubt that anyone's home oven has ever approached equilibrium, but even so, yes, various parts radiate at different intensities and that tends to eventually equalize the temperatures - if there are no other losses at one place or another.

So that's interesting, but note that the quoted passage applies at 330C, or 635 deg F, and I don't know anyone who bakes bread at that temperature. Since the intensity of the radiated infrared energy goes with the fourth power of the temperature, the net intensity is going to be a lot less - just about half as much, if your oven is at 230C (about (500/600) ^ 4).  In fact, the quoted passage says just that near the end.

One place where all three are seriously in play - radiation, conduction, and convection - is in a tandoor-style oven.  You slap a thin piece of dough onto the hot oven wall.  There are glowing coals at the bottom - radiation.  The hot oven wall conducts heat into the dough, there's your conduction.  And the flow of hot air out the top of the oven, there's your convection. Add to that a bit of smokiness if the tandoor is fired by wood and it's no wonder the results are hard to duplicate at home.  The closest you could come in a home oven is to use a top broiler coil, a preheated baking stone or steel, and a convection fan.  But the broiler elements tend to burn badly in a spotty way, not ideal, and it's hard to get the right balance of heating modes.

ReneR's picture
ReneR

"note that the quoted passage applies at 330C, or 635 deg F"

Ah, yes. That's another interesting point in the article. According to my friend, in real conditions, the pizzaiolo thinks their oven is that hot (pointing a digital hand held IR thermometer through the opening), but actually it is only that hot in the upper dome and the focal point, but much lower in other parts (not much convection). Hence why they tend to move the pizzas around as they bake. The floor would (mostly) be in the home oven range (250C) my friend thinks and that's why he even bothered to try and make pizza at home.

His preferred method is to put the pizza stone on the top rack under the grill/broiler which is at full blast for at least 45min and then take it a position down and put the pizza in, reducing the broiler a tiny bit or switching on the fan (grill + unheated fan). I have tried the first of those and it worked a treat, but had not realised that is because, in effect, a pizza cooks from the top down more than from the bottom up. Now it makes sense. Not too different from the tandoori example.

BTW, since the thread is about steam, my friend thinks that the article maybe doesn't take steam into account enough as the steam from the toppings is not insignificant (if you a baking 3-4 pizzas at the same time, or 50-60 loaves) and there is also H2O from the wood burning. So the oven is not as 'dry' as the article seems to imply. 

tpassin's picture
tpassin

I think you are right on about the air in the oven being more humid.  About the baking conditions in a big wood-fired pizza oven, it's more complicated because the fire is usually still burning.  The pizza is moved around because otherwise the side facing the fire would burn. and also the temperature distribution is so uneven that the pizzas have to be moved to make up for it.  But the potential burning is probably the main driver.  At least it was for me when I had a wood burning oven.

tpassin's picture
tpassin

That citation (or nearly the same work) is available without charge or signing up to anything at

https://arxiv.org/abs/1806.08790

AsburgerCook's picture
AsburgerCook

The member who posted the Italian Rolls recipe I was going to try, was adamant about lining the inside of the oven with clay tiles. I've seen that elsewhere, particularly for home-made pizza ovens. Why add those tiles if not to increase (improve?) radiant heat, for its impact on the dough, right?

tpassin's picture
tpassin

Why add those tiles if not to increase (improve?) radiant heat, for its impact on the dough, right?

The radiated heat is determined by the temperature of the material and how good a heat absorber it is at the temperatures involved (infrared radiation for home baking temperatures). (Material with the best radiation absorption are also the best emitters of  radiation). Those tiles won't radiate more than unlined oven unless they are much better absorbers of infrared, which is unlikely.

More likely is the effect of the tiles on moisture absorption and thermal conductivity.

Precaud's picture
Precaud

If radiant energy played a large role in normal cooking (except for a broiler element), then a convection fan would have much less effect

I think this is a wrong conclusion.

First, we have to acknowledge some facts re: heat transfer mechanisms between objects/materials; conduction (objects in direct contact), convection (objects surrounded by air), and radiant (direct infrared radiation). All ovens have all three modes occuring simultaneously in varying degrees.

: Convection really works the same as conduction; the only difference is, one material is gaseous (the atmosphere) and not a solid.
: Conductive heat transfer increases with temperature differential, moving toward the cooler surface, and lessens as they reach equilibrium.
: Air has far less thermal mass than a solid. Therefore it has little to give and is quickly cooled to the temperature of the solid at the solid's surface.
: Using the air to transfer heat is by far the least efficient method of the three.
: Most bakers (and oven designs) have focused on it because a) it is conceptually easier to think about, b) easier to measure, and c) it's inefficiency makes it easier to control.

Also, the term 'convection' in ovens specifically refers to forced air movement in the oven chamber.

The air movement increases transfer efficiency by breaking down the temperature boundary layers that form outside/around the cooler solid surface. Without air movement, those layers are relatively stagnant and effectively 'insulate' the solid object (imagine a 'halo' of layers of temperature differential).

To your point, radiant transfer is not affected by any of this. And it is more effective at breaking down the boundary layers than air movement is.

I always thought that radiant energy might have more of a role than assumed in the case of ovens, as trapping radiant energy is an important part of what ovens are supposed to do

I totally agree with ReneR's statement,  IF the object being heated is doing the trapping.

Designing and building passive solar heaters has changed the way I think about baking ovens and improving them. High-mass ovens only make sense if you use then continuously 24/7. Or are OK with really long preheats. I now focus most on improving radiant transfer, making it as even and consistent as possible all around the object being baked. Generally speaking, it is much better to use radiant immediately than to store and re-radiate it later.

 

tpassin's picture
tpassin

The air movement increases transfer efficiency by breaking down the temperature boundary layers that form outside/around the cooler solid surface. Without air movement, those layers are relatively stagnant and effectively 'insulate' the solid object (imagine a 'halo' of layers of temperature differential).

That's so (although at the sizes and air velocities involved in an oven the boundary layer is going to be thick anyway). It seems that it's time for me to think harder about ovens and their heat transfer.  Up until now my thinking has been mostly influenced by the 4th power law and the notion that it would preclude much radiant heat transfer. I thought that you needed to have temperature high enough to be nearly visible (like gently glowing coals) before it would be able to play an important role. I looked at an oven mainly as a way to contain all that hot air.

I suppose that if we had an experimental oven that could keep the walls at baking temperature but contain a vacuum we could learn right away how important the air vs radiant heat balance is.

Now that I think about it, when I used to live at 6000 ft elevation, I didn't notice much difference in how the oven baked. I'm not sure if that's enough difference in atmospheric pressure to matter here but at at least it's in the direction of giving more importance to radiant heating.

Precaud's picture
Precaud

I thought that you needed to have temperature high enough to be nearly visible (like gently glowing coals) before it would be able to play an important role. I looked at an oven mainly as a way to contain all that hot air.

As did I. It's conceptually easy, and partially true.

Like the other modes, radiant transfer efficiency (rate of transfer) is also proportional to temp diff.

I suppose that if we had an experimental oven that could keep the walls at baking temperature but contain a vacuum we could learn right away how important the air vs radiant heat balance is.

Or, go the other way. Keep the atmosphere but have low-mass, highly-reflective walls. No need to preheat; it does not attempt to store any heat. Like the flyweight Walmart 32L toaster oven does. The air temp inside will measure WAY lower than the set temp, yet it bakes 30-50% faster than a similar conventional convection oven with preheating.

 

AsburgerCook's picture
AsburgerCook

I dunno, you guys; I always thought of an oven as a way to have a fire inside the house! The stove burners put heat at the bottom of something, like a pan. The oven puts heat around something, like a chicken.

That being said, I'm learning a boatload on this thread about how convection, radiant heat, circulation, and energy transfers are working in the oven. It's why I wondered why we're trying to get billowing clouds of steam. Why not just use hot vapor, right?

I'm re-thinking entirely, the whole concept of crusts and how they're formed.

ReneR's picture
ReneR

As you will have seen in my other post to Lance, I have been engaged in dismantling my oven in order to change a blown convection fan heating element. Made me reflect on a couple of the points you make.

Interestingly, I found two 'insides' in the oven. The immediate chamber which is made of heavy panels with matt black enamel(?) finishing, and then this was encased in a shiny (thin stainless steel?) outer chamber, along the lines you suggest.

Clearly the outer chamber is there to reflect any radiant heat back into the inner chamber, but also to protect the outside of the appliance from getting hot by keeping the radiant heat all inside (there is also insulation between the outer surface of the outer shiny chamber of the oven and the walls of the appliance).  

So, the question now in my head is: why have the matt black heavy interior chamber? It seems a little like it has the role of the tiles/bricks AsburgerCook talks about in the original recipe. If I remember correctly, good absorbers of radiant heat are also good radiators of radiant heat, but they are also bad conductors of heat. So, they absorb heat, store heat, radiate heat back into the chamber, but also attenuate its conduction towards the walls of the appliance. So the outer reflective chamber is there to take care of any residual radiation escaping the walls of the inner absorbent chamber and the insulation on the outside of that is there to ensure that any residual small conduction does not make it to the walls of the appliance. 

Now, moving to your post and the original question about steam, I was left pondering the following, from this part of your post:

 Conductive heat transfer increases with temperature differential, moving toward the cooler surface, and lessens as they reach equilibrium.

So, agreeing that convection is a special case of conduction, my reasoning went as follows:

  • Loaf goes into the oven. Big temp differential/gradient. There is moisture on the surface and interior of the loaf and in the air circulating through forced (fan) or natural convection if we add water/steam. High convection and conduction heat transfer (separate question: might steam be more efficient in convection energy transfer than air?).
  • As the loaf heats, temp differential reduces and convection/conduction heat transfer reduces, so radiant heat comes into play more. Also, as moisture reduces due to added water/steam being exhausted and the surface of loaf drying, the drier hot air is now also drying the loaf surface. The surface starts to caramelize/burn from the radiant heat in conjunction with the drying. --> Radiant heat gains greater prominence as the bread/oven temperature gradient falls off?     

Just thinking aloud here, but might this dynamic view of the interplay between the 3 heat transfer mechanisms help explain some of the issues we have been debating in the thread?

tpassin's picture
tpassin

If I remember correctly, good absorbers of radiant heat are also good radiators of radiant heat, but they are also bad conductors of heat

It's correct that a good radiator is a good absorber of heat, but that mostly has to do with the surface properties.  How good a conductor a material is depends on its bulk properties.

The absorber vs radiator thing is easy to understand, BTW:  Take an object that's isolated and heat it up by shining radiant energy evenly on it. Let its temperature come to equilibrium.  Then it is radiating all the heat it's absorbing.  Otherwise it would  be heating up or cooling down and wouldn't be at equilibrium. A perfectly absorbing object - one that absorbs as much energy as can possibly be absorbed - is also radiating as much as can possibly be radiated.

The reverse is also the case: shiny reflective surfaces don't absorb heat well.

tpassin's picture
tpassin
  • Loaf goes into the oven. Big temp differential/gradient. There is moisture on the surface and interior of the loaf and in the air circulating through forced (fan) or natural convection if we add water/steam. High convection and conduction heat transfer (separate question: might steam be more efficient in convection energy transfer than air?).

I hadn't though about the influence of water vapor on baking dynamics before this post.  It could add complications. Moisture in the air reduces its density - this is an important factor in aircraft performance, BTW. Reduced density would reduce the ability of air to transfer heat to a surface by moving along it (convection) but (I think but am not sure) it would increase the heat capacity of that moist air. Moisture would also absorb some of the infrared radiation from the walls of the oven.  That effect should tend to level off as the moisture heats up.

  • As the loaf heats, temp differential reduces and convection/conduction heat transfer reduces, so radiant heat comes into play more. Also, as moisture reduces due to added water/steam being exhausted and the surface of loaf drying, the drier hot air is now also drying the loaf surface. The surface starts to caramelize/burn from the radiant heat in conjunction with the drying. --> Radiant heat gains greater prominence as the bread/oven temperature gradient falls off?  

This sounds about right. The heating up of the loaf's surface causes it to emit more radiant energy, so the net heating from radiant energy will decrease as this is going on.  Remember that the flux (intensity) of the radiant power is very sensitive to the temperature. So the balance between radiant and non-radiant heating is going to change quite a bit between say, 375 deg F/190C and 425 deg F/218C.

 

Precaud's picture
Precaud

So, the question now in my head is: why have the matt black heavy interior chamber?

This is traditional air-temp-based oven design thinking. Make the walls of the inner chamber black/dark so they collect and "hold heat" and help keep the air inside the oven at a stable temp. With gas-fired ovens, this is pretty much required, as the period (length) of the gas flame on-off cycle (aka "duty cycle") is by necessity fairly long. As is a long preheat period.

Radiant-based designs can avoid all this by using lightweight shiny reflective interiors, electric heating elements, and shorter duty cycles to give better control of the heat transfer. They do not even try to use the air inside the oven as the primary heat transfer mechanism. And it is much more efficient.

Radiant heat gains greater prominence as the bread/oven temperature gradient falls off?

That's a question which is still oven-air-temp centered. It's hard to give up old ways of looking at things.

As the loaf heats, temp differential reduces and convection/conduction heat transfer reduces,

Yes, but...

so radiant heat comes into play more.

That makes it sound like conduction is the dominant force, and radiant was hibernating, waiting for conduction to ebb. With exposed electric heating elements, the surface temperature of the heating element is very high, the temp differential is always very high, so radiant is always present and always the strongest mechanism. It's the air in the oven which has low thermal mass and whose temperature fluctuates so much (easy to heat up, and just as easily loses it [gives it up] to anything cooler it is in contact with...)

Perhaps it's useful to imagine radiant heat transfer acting like magnetism. Technically, it is an electro-magnetic event...

AsburgerCook's picture
AsburgerCook

Empiricism is essentially, "I only know what I personally have experienced." Most of the world runs on that philosophy, sadly. Unfortunately, it also leads to people arguing that "your facts are different from my facts, so I guess we each have a right to our opinions." Or saying that facts are simply a matter of opinion. Yeah. Right.

I spend a lot of time looking into nutraceuticals, holistic health and whatnot, and I'm well-familiar with how "knowledge" is always a moving event. New discoveries suddenly either explain or contradict "well-known" truth(s) and previous knowledge.

However! All that being said, there are some facts that remain the same throughout long periods of time, like centuries. The boiling point of water, for example.

Facts are events of reality. Truth is our statement about those facts, and whether or not our statement matches reality. Knowledge is a collection of information: It may be true, or false. Hopefully, wisdom is a collection of factual knowledge, based on reality. At least that's my story, and I'm stickin' with it. :-)

What's great about Fresh Loaf is it being a real-world research lab, with people willing to write out what they're finding, discovering, and what works or doesn't. It's a gigantic learning center, and we're fortunate that the archives are readily available.

Ayn Rand argued that Objectivism (her own philosophy) would be the opposite of Empiricism. The idea is that objective reality is what it is: Existence Exists, one of her axioms. 

To that extent, I think some number of us here are trying to find those objective facts and events that will render the same bread, repeatedly. Having a recipe "etched in stone," as I'll think to myself. :-)

Much like quantum physics; we may not know (yet) why or how it works, but we can use some of the principles in everyday life because they always work that way. So too with bread: We may not know the underlying details of physics or technology, but, as we also might say, "Hey... if it works, it works!" :-)

And that's why I wondered if we need steam? Or are we really looking for humidity and moisture, regardless of seeing steam. I can't even start to list the countless Web postings about how to get Steam! Like, if you can't get steam, forget making whatever that bread recipe is. That's ridiculous!

We can't make pizza at home because we don't have a wood-burning oven? As we can see above, that's not true at all. Maybe we have to be a bit more creative, but there's a solution. One of my favorite sayings: "The answer to almost any question is contained within the proper phrasing of the question." The trick is the proper phrasing part.

ReneR's picture
ReneR

At the risk of veering too suddenly from objectivism and empiricism to complete subjectivism and metaphysics, I think I have been punished for hubris and  delving too much into their secretes by the Oven Gods!

Last night, quite late, and with a 25% wholemeal spelt loaf proving, I turned on my oven as usual on convection fan to pre-heat it and my DO to 220C. Suddenly, something blows and the fuses in the house are tripped. Turn off the oven and re-establish the electricity supply in the house, turn on the oven again and think 'phew, it is still working' as the fan was going round, only to realise 30min later that the temperature is actually going down in the oven. By this time it is too late and I am too tired to try and figure out what has happened, so I just throw the banneton into the fridge and go to bed.

In the morning, with an obviously overproved loaf in the fridge, I find that the other functions of the oven (top and bottom heat and combinations) are working so decide to try and bake the loaf, aware that it will not be much good. The top + bottom setting got to 220C, just, but the heat was obviously more uneven, with the bottom much much darker and then the top needing to go a little under the top heating element once the lid was off from the DO. There was hardly any oven spring and the loaf spread out a lot, but it seems the loaf is still useable.

Oven failure

I'll engage in some atonement libations  with dinner tonight and spend some time on YouTube looking for fixes for the blown heating element and see if I can buy a spare somewhere if it is fixable by me, or start looking around for the SMEG servicing online.

Oven

Any suggestions on how to change a convection fan heating element on a SMEG 90cm mini range electric oven/gas cooker will be most gratefully received.

 

albacore's picture
albacore

Not done a Smeg, but have done a few others. Generally a case of isolating the power and pulling out the oven. There's usually a removable back panel that gives access to the circular fan element terminals to change it. Also a panel inside the oven to remove and the element comes out that way.

Always worth checking with a multimeter at the terminals to confirm it's blown, though sometimes there's a small hole in it.

Obviously only do this if you are confident on working on 240v equipment.

Ransom spares is a good place for cooker elements. They might have a few instructional videos of their own.

Lance 

 

ReneR's picture
ReneR

Many thanks Lance for giving me the courage to get my toolbox and try to do the repair myself. I had to take both the back of the oven and some insulation off to unplug the wiring to the element and then also take the inside panels of the oven out and unscrew the element holder from the inside, as you suggested, but the element itself is pretty standard.

It looks a little distorted and I suspect that it may have very slightly touched the metal fan it is in effect wrapped around as a result. No actual blow-out or damage on the surface of the element, but my multimeter battery was flat, so I couldn't check for electrical integrity and since the replacement part was pretty cheap (£12), I decided to order a new one anyway. 

I have used eSpares in the past and they were OK, but found it on Amazon, so included it with some other stuff I needed, to get free delivery.  Not an OEM part, but apart from the power rating (2500W instead of 2700W) all dimensions and connections are the same as what I took out. Hopefully no bad surprises when I get the delivery.

 

ReneR's picture
ReneR

Got the replacement heating element from Amazon today. It's not an OEM part, but have to say it looks better made than the OEM part that failed. 

Fitted, wired, and tested and all look well. Very happy with that. For £12 and about 4h work, I have all the oven functions back. Let's hope the new part will last well.

squattercity's picture
squattercity

Fascinating, Rene. I have a giant oblong dutch oven that is heavier than my round one and has a more secure seal. Bread in it has also been variable: sometime I get a fantastic, super-high rise, sometimes more compression, sometimes a perfect crispy crust, sometimes tough & heavy.

Rob

ReneR's picture
ReneR

It was really funny with this DO. I went off to a catering trade shop and treated myself to a new batard banneton and the new oblong DO in which to bake the batards.

Got home all excited about all the new possibilities my new kit would provide and confident about the outcomes, now that I have been achieving consistently good bread with my old setup. How different could the shape of the banneton and the DO be in terms of making bread, right?! 

Then the results brought me down to earth! The bread was not bad in any way, but not of the level I had been achieving before. I am telling myself that it adds to the fun trying to figure out all these variables that are involved in making bread. Shows how even such a basic product has immense complexity.

AsburgerCook's picture
AsburgerCook

Tom, I read this from the older thread Rene linked (Thank very much, Rene!):

Steam does two things for you; it brings water directly to the dough which helps to fully gelatinize the starch forming a shiny, waterproof, gas tight membrane that prevents CO2 from escaping through the surface (thus forcing dissolved CO2 in the dough just under the skin to form blisters when it comes out of solution as the dough temperature rises to exceed the temperature at which the CO2 can remain dissolved).

The cooked surface is also physically strong and cannot stretch to accommodate expansion of the trapped CO2 (oven spring) and will thus facilitate fracture along the lines defined by your lame when you slashed the dough (or randomly at weak spots if you forgot, or slashed ineffectively).

So it seems I'm going to want to get that high temperature for the thin crust. Plus, I'm (slowly) getting there with the "gel" concept comprehension. 

I'd thought the underside of that membrane was slowly turning into the underside of a crust. I now see that it just forces its way up through the existing "skin" (membrane), causing blowouts. 

Has anyone ever pointed out that baking bread is complicated? If not, I'm offering a public service announcement to that effect, in the hopes it may help future generations! Jeez.....