Adventures in Steam

[Mike Nolan]

As I noted a few days ago, I've been experimenting with using some heat-safe food grade silicone tubing to add water to a hot cast iron skillet to generate steam in my oven without opening the door. The first bit of good news is that the tubing doesn't seem to be causing a heat leak around the oven door, so I can leave it in most of the time.

I've been doing some math on steam generation. My bigger oven is about 3.6 cubic feet. (It'll hold a full size sheet pan but with almost no room for air circulation, so I stick to 3/4 sheet pans.)

In some tests, it looks like I can put about 20 CCs of boiling water into the pan via the tubing and have it vaporize in a few seconds. When water converts to steam, it expands to about 1600 times its volume. So 20 CCs of water will generate about 32,000 CCs of steam or about 1.1 cubic foot, meaning the oven chamber should be about 1/3 steam briefly.

I don't know how that compares to the amount of steam you get in a commercial steam injection oven each time you pull the lever, because I've never used one. I'll see if I can find some data on one.

A possibly major difference between a commercial steam injection oven and a home oven is that the commercial oven has vents that can be sealed to keep the steam in for a while, a home oven is probably far less air tight. (I know there's some kind of vent at the back right because I can feel the heat there when the oven is in use. And after the oven has been on a while, a fan kicks in, I'm assuming it pulls some of the air out of the oven so it would pull out steam as well.)

I will be taking some pictures showing my setup, and I'm going to try to take some videos showing how much steam it generates, possibly compared with the 'pour water in the pan' method.

The videos will mostly be with the door open, though I may see if I can set the camera up to shoot through the oven door. Where's Alton Brown's oven camera when you need it?

I'm also getting ready to try my steam generator with some recipes I know, so I can compare the results. I may have to try to bake a recipe at least 3 times, once without steam, once with the 'pour the water in the pan' method and once with the tubing method, and maybe a few other ways.

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[BakerAunt]

I look forward to hearing more about this experiment.

[aaronatthedoublef]

This is REALLY cool. I look forward to hearing more. Keeping the door closed (or mostly closed) while adding the steam through a tube is inspired. I will have to try that. I worked at a place with a steam injecting oven but they did not let me use it and the shift lead did not know how much steam it actually injected.

And always turn off the convection fan while adding steam with the door open.

[Mike Nolan]

About the only thing I use the convection fan for is the first 10 minutes of fruit pies.

I also posted about this on the BBGA forum, and got an email from a baker who says he thinks I'm getting plenty of steam, all you need is enough to get the crust damp.

I found the instruction manual for an oven that uses steam for both baking and cooking, it has a tank that holds 950 ML of water, and it says that'll last about 50 minutes. That's 19 ML per minute, which is pretty close to what I found I can do in a single burst with my tubing setup. Of course with bread, steam is really only useful in the first 10 minutes or so of baking.

I think I've identified about 8 different methods I want to test. My plan is make up a large batch of Peter's Pain de Campagne (I've used it for other tests, and the addition of a little whole wheat flour to a lean dough adds some nice color and flavor, so the bread won't go to waste, though it might go to waist) and retard it in the refrigerator overnight, so that each test has pretty much the same conditions, dough that has been out of the refrigerator for about 2 hours.

I'm also going to see if I can get some time-lapse photography shots of the bread baking through the window in the oven door. Not sure if there's enough light inside for that, even with the oven light on.

[Mike Nolan]

The Equipment:

This is 1/8" interior diameter (1/4" exterior diameter) food grade silicone tubing, which you can get from home brew suppliers.  It took about 27" of tubing for my oven.

The funnel is one of several we got at a kitchen supply store.  I'm using two brass nuts as weights to make sure the tubing stays in the pan, though in my initial tests I didn't use them and didn't see any problems with the tubing falling out of the pan.  One nut is a bit larger than the other, the hole in the smaller one is a tight fit for the tubing, so it shouldn't move around.

The Setup:

There's a gap between the oven and the cabinet, and I'm using an angle bracket to hold the tubing and funnel in place.  I also put in a small wedge just to keep everything from shifting around.  During production I don't want to have to deal with things other than the bread.

Here's a view of the full setup. When not in use, the tubing can hang straight down and it doesn't interfere with the cabinet door or touch the floor.

Here's a view of the tubing sitting in a 9 inch cast iron pan.  I've added about 20 CCs (4 teaspoons) of water just to show how much that is before it evaporates.  It takes 3-4 seconds for that much water to go down the tubing.

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[aaronatthedoublef]

Neat. Would a bigger funnel allow for more water? Or would it be limited by the tube? Not that you need more water.

[Mike Nolan]

I took some fluid mechanics courses in college back in the late 60's, but I don't remember the formula for the rate water can flow down a pipe due to gravity.

Fortunately you can find almost anything on the web these days. It looks like 1/8" interior diameter tubing will have a gravity flow rate of 2-3 teaspoons per seconds, depending on the friction of the tubing.

It appears that the interior diameter of the funnel is the limiting factor so far.

I've got a funnel that fits outside the tubing, as far as I can tell without leaking, it allows a faster flow rate. I think I got over 1/3 cup into the pan in under 10 seconds, which is consistent with the flow rate I computed online.

1/4" OD tubing struck me as about the largest I could use without creating a heat leak at the oven door.

In tests with a syringe instead of a funnel, I can get 60 CCs of water into the pan in under 10 seconds, but it looks like 1/2 to 2/3 of it doesn't flash to steam, though it would continue to create steam for a minute or two. A larger or heavier pan might handle more water at a time, but I'm not sure it is necessary, the bread tests may tell me more, I'm hoping to do them next week.

[Italiancook]

This is fascinating, Mike. Thanks for the photos. I'm looking forward to next week's bread tests.

[Joan Simpson]

Interesting about the steam.

[aaronatthedoublef]

When do you go into production? Can't wait to see this on Kickstarter!

[Mike Nolan]

Today is steam test day.

I'm taking pictures through the oven door window every 15 seconds, I'm hoping to be able to stitch them together into a short video. They're not the clearest of pictures, because I'm shooting through the oven door window, but I think I can see changes from one shot to the next. I'm also taking a picture with the door open at the 10 minute mark (when I rotate the loaves and remove the steam pan, if any water is left) and one just before I take the bread out.

The first 3 loaves are out (no steam, water sprayed on sidewalls, and pan of hot water in oven before bread goes in.) The more interesting tests are yet to come, with my steam tube. I'm also going to do one in a dutch oven, though I won't have shots of it during baking, obviously.

I do see a few differences in the crust between the first three loaves, though the amount of oven spring doesn't seem to have been affected much. I won't be cutting in to them to get an interior photo until later on. I don't know if I'll have the pictures posted until tomorrow, the baking will be going on until at least 7PM. (I will have to take a break after the next one to recharge the camera battery.)

My wife had no trouble finding takers for some free French bread.

[skeptic7]

That sounds like a well thought out experiment! You and your wife must be very popular at work.

[Mike Nolan]

Yes, my baked goods always get a lot of compliments. One of the former staff members used to be a chef, he says my Texas Chocolate Sheet Cake is just fantastic. He switched jobs last year and now works on the downtown campus, but when I sent in a Texas Chocolate Sheet Cake last fall, my wife dropped him a note and set a big chunk of it aside for him to pick up that afternoon.

The former chair of the department of Agronomy and Horticulture is a grill master (in addition to being one of the leading experts in turf grasses), and he hosted two dinners that were silent auction fund-raising items for student groups. We volunteered to send in some bread, and I made two Celebration Challahs (2 layers tall and about 22" long) that everyone really appreciated, Roch said he didn't recall the last time he ate that much bread. (I posted a picture of one of them here at the time, it came out about as perfect as I've ever had one come out. That picture isn't coming up for some reason so I've reposted it below)

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[Joan Simpson]

That is beautiful Mike.

[Mike Nolan]

Well, the set of pictures won't be quite complete, I ran out of space on the camera's memory card mid-way through test #6. I deleted some unneeded stuff (which I should have done last night) and was able to get the last few minutes of that bake, but I missed the shot at the turn. I think I cleared enough space for the final 2 tests, but I'll double check that before the next one goes in.

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