Plugging oven vents with foil
I've got an old eye-level oven (Defy) for which there is no setting to turn off the convection fan. I usually bake in a dutch oven because of this.
When I've baked on the baking steel, it has always felt like my trays of water are dried out in the 20 minutes of steaming time, and although I can see bubbling on the bread which indicates there was some moisture during the early part of the baking it has always felt like there may not have been enough.
I read somewhere about blocking the oven vents with aluminium foil and it seemed to have worked much better in my most recent bakes on the steel. There are two side vents on the door, I tried blocking the bottom one more thoroughly and the top one more loosely, so during baking you can see a steady stream of steam coming from the top vent.
Plugs are only added before baking and removed after 20 minutes along with the trays I'm using which are now a lot fuller than they were before at time of removal.
So, it seems to have been a good technique, although I must admit to being nervous that there would be a steam buildup of some kind in the oven.
Has anyone else done similar?
I have tried to plug mine a few times when I was doing an open bake with different steaming options, and I was having some thermal gradient issues. I think those vents are strategically placed for thermal distribution purposes so by plugging them up it might change the air flow and in turn changing a thermal dynamic aspect of the oven. This is just a guess as I don't know that for sure. I don't do an open bake nowadays, so I am glad I don't have to deal with that anymore.
I’ve always been too scared to try anything like that with my oven Jon. I thought I had read something in the forums here warning against it, but I cannot find that reference.
Benny
If so, the only question would be how it may affect the oven's temperature control.
If a gas oven, you do NOT want to block the vents since they also give the spent combustion gases a route to escape. If they can’t, the burner flame might snuff out.
One other thought: 20 minutes is plenty long for steaming. Longer won’t necessarily improve the bread. Better to have lots of steam for the first 5-10 minutes.
Paul
Thanks Paul, yes electric oven. Thanks for the advice!
Interesting advice about 15 minutes. What would be the effect of going "too long" with steam (20 minutes in this case), would it be that the bread can keep on opening up for too long, or the crust would get leathery or something like that?
I would probably watch through the glass door to monitor the oven spring, but once again, old oven and issues with the oven light, so difficult to do.
but here's what the King Arthur site has to say about steaming too long:
"If steam is so great, why finish in a dry oven?Steam is vital during the oven-spring period so that the surface of the loaf remains moist and expands easily. However, once the yeast has died and the loaf is set, moisture is no longer a friend to your bread. Too much moisture throughout the bake can lead to a thick, rubbery crust."
In general terms, then, remove the steam once oven-spring has finished.
For something with a small cross section, like a baguette, 5-10 minutes of steam may suffice. For a larger loaf, such as a boule or a batard, maybe 10-15 minutes or 15-20 minutes might do. You may have to do some observations to see how things play out with your oven and the breads you make before settling on an optimal duration for steaming the oven.
Hope this helps.
Paul
I’ve recently been doing time lapse videos of some of my bakes since I switched to open steam baking. While doing so I noticed that the bloom and oven spring were still going on when I vented the oven to start “dry” baking. So because of that I’ve extended steam baking from 20 to 25 mins. Now whether or not that makes much of a difference in the overall rise and bloom I cannot be certain. However, I am more convinced that the crust is thinner with open steam baking and maybe a bit thinner yet with the extended steam baking. All anecdotal I realize.
Benny
The burner might not be the only thing to snuff out!
I have a GE electric oven and I plug the upper vent with a towel before I pour water in my steam pan. I make sure it's as tight as possible and don't lose any steam. After my steaming (I've recently dropped from 20 to 15 minutes), the first thing I do is remove the towel. If I have a nice plume of steam roll out, I know I had enough in there during the bake.
Thanks Troy, curious to know - the door of your oven opens downwards, or to the side? Mine opens to the side and there is a top and bottom vent in the oven door itself. What is your oven layout like - only top vents?
Jon, It’s a large, single door that opens down.
I think there may be a vent in the door, but I never see steam rolling out. I need to check that closer.
I only have one vent that I plug in the top.
In support of Ming's comment, note this older post from the online forum Cooking for Engineers: “The vent is necessary to maintain an equal temperature through out the oven. Air is typically drawn in through the bottom of the oven door, and then moves by convection out the top of the oven…. Open your oven door and have a look at the door gasket. Notice the gap at the bottom? That's where room air comes into the oven…. If you block the vent, the oven temperature will be lower than you expect. That's because without any venting, the air in the oven stratifies, that is, the hot air rises to the top and the relatively cooler air stays at the bottom. Because the oven temperature sensor is near the top, it will sense the hotter air, and so the middle and lower parts of the oven will be cooler than your setting.”
I don't think that most home ovens work the way people imagine. Yes, I'm sure the vents help reduce stratification, but I think that what goes on early in the bake is fairly different from our usual picture.
My oven setup is like many's. I have an electric oven in a range. It has vents around the oven door and also (unlike many) another that lets hot oven air escape over the cooktop. The oven has both an upper and a lower heating coil, with only the lower one used in normal baking. It's not a fan oven, though there is something going on at the middle I don't quite grasp.
I have a rock-filled steam pan on the lowest oven shelf and a baking steel in a rack in the middle position.
An ordinary oven is not a sealed pressure vessel. Any overpressure will leak away through any and all joints and openings. Blocking the vents may slow this a little. Some of that leakage of hot water vapor may get into the controls and electronics, which isn't likely to be good for them.
So ... I slide a loaf onto the steel and pour water into the steam pan. Steam immediately billows out. The steam pan temperature rapidly drops near to the boiling point of water, and hot water remains in the pan for a long time. This will keep the oven air moist but it won't produce billows of steam any more.
The initial burst of steam will condense onto the surface of the loaf, heating it up and helping the surface starches to gelatinize and the sugars to melt. The air above the loaf will cool down to near the boiling point of water. The steel will keep pumping heat into the loaf from the bottom, causing it to heat up and expand. The water remaining in the steam pan will keep the lower part of the oven relatively cool. In my oven, even near the end of the bake, the temperature in the lower part of the oven will usually not rise much higher than 300 or 330 deg F/150C-165C because of the water remaining in the steam pan.
At some point, the oven sensor will notice that the oven air has dropped below the set point and turn on the bottom heating element. But the baking steel and steam pan block most of that heat from heating the upper chamber of the oven. This helps slow down the cooking of the loaf's surface. Only after the air can convect and circulate enough past the steel will the upper chamber heat up much. If your oven turns on the upper element to try to heat it up, you will be broiling the bread and that's not really what you want.
So the oven temperature setting is almost irrelevant during this first part of the bake. Don't believe me? I've been turning my oven setting down to 250 - 300 deg F/120C - 150C for the first 8 - 15 minutes of the bake and the bread comes out at least as well risen and I think better - and with the same total bake time - as when I didn't turn it down. The crust is the same, as best as I can tell.
I have been blocking the cooktop vent during at the start, but only while steam is visibly venting. That only goes on for the first minute or two.
I know that some people have rigged up systems to keep injecting steam into the oven, and of course that changes things. And different ovens have sensors in different places and use different heating strategies. So the details for your oven will be different than for mine. But I'm pretty sure that few of them work the way we naively thought. Stratification because of blocked vents is the least of it.
TomP
I think there are two reasons electric ovens have a vent:
1) for safety - if there was no vent, then pressure could build up in the oven as things heat up and moisture turns into steam, so when the "operator" opened the door there would potentially be a dangerous blast of hot moist air issuing forth into the face of the operator.
2) to keep the atmosphere inside the oven relatively dry, so that baking of pastry and the like will be successful without sogginess.
Fortunately for me, the vent in my Bosch oven is in a little top hat set into the roof of the oven cavity near the front. I was able to devise a pivoting disc valve to cover the vent. I close the valve for steam injection and stand and then open it for the vented heat phase.
Lance