The Proof Is In The Box

Making bread dough is simple — it’s just flour and water, with some salt and yeast if you want to make things easy on yourself. Turning that dough into bread is another matter entirely. You need to punch that dough down, you need to let it rise, and you need to knead it again. At home, you’re probably content with letting the dough rise on the kitchen counter, but there’s a reason your home loaf doesn’t taste like what you would get at a good bakery. A bakery has a proofer, or a box that lets dough rise at a temperature that would be uncomfortable for humans, but perfect for yeast.

The leavening cell is a DIY proofing box that keeps dough at a steady 26° C to 28° C, the perfect temperature for making bread, pizza dough, and even yogurts. [vittorio] made this and the results look great.

The design of this build is simple enough and made out of 20×20 aluminum profiles shaped into a cubic frame. The outside of this box is 6mm thick wooden panels coated on the inside with a heat-reflective insulating mesh. Inside of that is a frame of metal mesh to which a six-meter long cable heating element is attached. This heating element is controlled via a thermostat with a probe temperature sensor on a timer. No, it’s not very complicated but the entire idea of a proofer is to have a slightly warm box.

You can check out the promo video for the Leavening Cell below.

40 thoughts on “The Proof Is In The Box

  1. My hack was to use a standard warming tray as a heating element inside a box made from foam board and a temperature controller. We had the warming tray, so my cost was ~$35 for a temperature controller and maybe $3 for the board. Version 1 had a circulation fan, but that proved unnecessary.

  2. Isn’t “26° C to 28° C” something like 78-80F? I’m not sure why that would be ” a temperature that would be uncomfortable for humans”?

    I thought bread dough liked it warmer than that.

    1. I use a home commercial model. It is all plastic and might not have great insulating properties. I set it to 104F

      My kitchen is no more than 55F in the winter, I hate paying heating bills, without the proofing box I couldn’t bake in here during that season.

    2. I do not check your conversion to non metric units, but it sounds reasonable. But I absolutely support “uncomfortable for humans” – at least in an office or work environment, where you have to wear any kind of clothes. If the temp gets that high, I start the air condition. Although I know people,who like that level of heat.

  3. I once put a thermostat, an incandescent lamp, a relay and an Arduino inside a styrofoam box (polystyrene box, whatever is called) for making yogurt. I told my wife to use it to make bread, she never tried.

      1. I do make bread sometimes, we have a bread-making machine and I always use it, as it works well and it’s fast and easy: throw everything inside, following the recipe order, press “Start”. I prefer her hand-made bread than mine, as she is way better cook than me.

        Maybe one day I will sneak into the kitchen and move her dough into my yogurtuino…

  4. This is only needed if you do the baking in an oven.
    My bread-baking machine uses its heating element to pre-warm the ingredients, mix them, add the dry yeast using a little solenoid, does several cycles of dough rising and kneading, adds and mixes additional ingredients at the end (so sharp nuts don’t wear out the non-stick coating when kneading) and finally bakes the bread, 5h30m in total, then beeps to wake me up so I can pull out the bread and let it cool early morning. Wonderful little machine, except that it’s closed-source and off-line.

      1. Mine adjusts the program based on the ambient temperature of the room.
        Software-wise it’s undoubtedly trivial, probably runs on an ATMega or similar, but knowing what the program should be is important.
        I immediately thought about liberating it with a custom controller, but I don’t fancy working it out myself and all the accompanying failed loaves that would involve!
        Also, I think 35C is a typical proofing temperature?

    1. It’d also be useful if you’re making buns or similar which require shaping, proving and baking – the breadmaker can make the dough but not turn it into buns. And clearly it does a much better job of proving than me, as the buns aren’t as good as the loaves mine bakes. I think a “prove” setting on the oven would be the best solution, but the lowest temperature on my oven is 50C. I don’t fancy hacking it, given it’s got its own circuit to the breaker…

    2. I used one for some time.

      First drawback: It beeps about 45min before the bread is finished, in case you happen to want to add raisins or nuts or something. But you can not turn that feature off and my bedroom is near the kitchen.

      Second drawback: The bread needs more time to cool after removal than I want to waste between getting up and breakfast. (a quick shower and dressing) so it’s not ready when I want to eat it.

      I would definitely need a robot which removes the bread from the machine 15 to 30 minutes before I get up. :-) Then I also could kill the beeper.

  5. My proofing box is a Koolatron peltier cooler running in “warming” mode, with a plain old wall thermostat (the kind intended for electric baseboard heating) put in the box, wired into the 12V power line. Easy peasy. Took a whole five minutes to plumb together, and it’s been running for about 10 years now.

    I run mine at 33C. Perfect for sourdough.

    1. Surprising the peltier copes with that, I heard they don’t last long with thermostat cycling due to mechanical stress it causes on the semiconductors. Modulated control with constant current is preferable.

      1. I’ve been using Peltier coolers in various applications for more than 3 decades, including multistage units down to -70C. There’s a huge incentive to modulate current for efficiency reasons, but I’ve never heard of or experienced failure due to stress on the elements, in cycling applications or not. Most failures I’ve seen are due to condensation and corrosion. Thermal coupling failure due to creep, yes, that too, and I can see how cycling can accelerate that. However, this is a pretty low-stress application: Holding a stable 33C from ambient 18-20C isn’t very difficult or thermally stressful, and there’s no danger of condensation.

    2. I also thought about the possibility to repurpose such e peltier cooler. They are very inefficient as coolers anyway. They are better at heating. For proper cooling I don’t see an alternative to a compressor driven device.

  6. The restaurant that I used to own did not have a proofer, there is really no need. We did put loaves of bread on top of the pizza oven to rise, but that was hardly well controlled. It worked fine though, 6 days all summer and all winter. Oddly enough I did build a proffer at home a few years ago as I like baking in the wintertime and we keep the kitchen way too cold. That uses an inexpensive temperature controller and a 40W incandescent lamp. It is big enough to hold 3 2 pond loaves.

    At some point I think I am going to drill a big hole in each side that I can either fill in with a solid plug so it will continue to work as a proofer, or allow me to put a fan on one side and a screen on the other side to make it more of a dehydrator. It is too tightly sealed for properly drying things a it is. It is interesting how often we use it for stuff. From bread to trying herbs and spices to the occasional cell phone that got exposed to the water.

  7. I’c confused – if you need to (and I normally just leave my bread in a warm sport in the house, but for a moment assume there isn’t any) you can just put it in the oven and set the oven on 28C! (which mine does quite reliably..) So why do you need a seperate box????

  8. 1. In the summer in areas where air conditioning is common, one could just increase the air conditioning temperature a few degrees, save some money, and do good to the environment all at the same time, at the expense of a bit of comfort (27C is less than a degree over what I anyway like to set our air conditioning to, but I know most people like it cooler).
    2. Otherwise, how about using the heated bed of a 3d printer?

    1. I prefer barbecued meat over boiled. It probably contains some more substances “Known by the state of California…” but I don’t care. :-) It tastes good. Nobody will life forever.

  9. I’m sorry but has someone ever tried making the pizza dough in a fridge – it is much better! In german that is called “kalte Führung” with a lot less yeast and a much better flavour of the final product.

  10. A proof box is only really needed if your ambient temperature is way too off.

    HACK: In cold climates, your oven light will keep the whole thing warm and fairly constant. My pretty standard BOSCH oven stays at 27 degrees for an ambient temperature of 20 when the light is on.

  11. While no amount of tech is too much tech, I’ve done yogurt (similar requirements) with just a gallon of hot water in a jug, sitting next to the yogurt culture, all of it inside the styrofoam. The water has enough specific heat to keep it cruising overnight, and everything is ready in the morning.

    A good tight styrofoam cooler is amazing.

  12. Hmm. Now I’m wondering if I can proof dough in my 3D printer enclosure. Reaching a ambient temperature of 26° C is no problem with an AC heated bed. Might need to add a fan to evenly distribute the heat though.

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