I love making bread, but finding time and a place to proof the bread is usually difficult.  I usually use the oven, but controlling the temperature is hit and miss, and then having to get the oven up to temperature and leaving the dough out in the cold doesn’t make amazing bread.  We’ve all seen those proving draws on BBC Bake Off, but where the heck do you get one of those from and besides my kitchen space is at a premium.  The next nearest option is a Brod and Taylor folding proofer, but even that is difficult to get hold of and the cost of the unit is quite high.

So on to the DIY

I’ve watched a number of videos about constructing a proving box and adding a complex temperature and heating solution.  All of those solutions were mainly american made and didn’t really explain how to build them or what was needed.

I decided to concentrate on the heating and control elements and worry about the box later.  I set out to do some research on Peltier devices and found a few YouTube videos for a cooler box.  Now the neat thing about Peltiers is that they generate both heat and cold, so all I needed to do was reproduce the Peltier rig that I had seen in the YouTube video.

I already had a 12 volt power supply and just needed some Peltiers and something to control the temperature, so a quick search on Amazon, and a pack of 5 devices was on the way http://www.amazon.co.uk/gp/product/B00GN2GP0S.  Also on Amazon I found a 12v temperature controller http://www.amazon.co.uk/gp/product/B00IL31PE8, this little controller comes equipped with a thermostat and the wiring is very simple – connect the 12v to the input, set the temperature using the DIP switches inside the unit and then connect the load (Peltier).

Never having worked with a peltier before I was keen hook it up to the power.  I started by configuring the control switch, setting the temperature to 35c, then hooking up the power, within seconds the peltier got both very cold and very hot at the same time, I was impressed and switched the power off.

Next I knew that I needed to distrubute the heat so as to not burn out the peltier, so I constructed a few bits of metal screwed down to a wooden block.  This time I was going to test that the thermostat was going to switch off the heat.  Initial tests proved that this was going to work fine, but I could smell something burning which wasn’t good.  I had just burnt out my first peltier :(.

Time to get some proper heat sinks

I didn’t have any heat sinks so needed to pop out and get some, based on the YouTube cooler video I had watched, I decided that I needed 2 of them.  I choose matching heat sinks which featured a quiet fan, then applied the thermal paste and sandwiched a fresh peltier between the two.  Then connected the power and switched it on.  My hand held thermometer showed this this one was working, getting up to a temperature of 65 degrees on the hot side and condensation on the cold side.

Now that I had a working rig, it was time to put it in a box.  I choose an old shoe box for this part of the test, cutting a hole in the side to fit the hot side of the unit in, fitted the thermostat and closed the lid.  It took about 5 minutes for the box to get up to 38 degrees, then the control switch kicked in and switched off the heat.  The temperature rapidly started to fall and after about 40 seconds, the power had switched back on, it then took a further 2 minutes for the temperature to get back up to 38 degrees.  Then I tried covering the box with some towels to insulate the box, this time the box held its temperature for 2 minutes.

Time to try some bread

I knocked up enough dough for a small pizza and left the dough in a covered bowl in my warming box.  After 30 minutes, the dough had risen very nicely, normally I’d need to prove it for close to an hour.  I knocked it back and stretched it onto a tray and returned the tray to my warm box.  After 15 minutes the dough was ready to cover and bake.

Next steps

I need to build a bigger box and put some insulation in it so that I can fit my baguette trays inside.  I also need to figure out how to increase the humidity inside the box so that the yeast thrives and makes the bread nice and light.

Second thoughts

Having built my prototype proofing box using a peltier, I now realise that I could have achieved the same if not better result by using a 12v ceramic heating plate http://www.amazon.co.uk/gp/product/B00UJ99FTO along with a single heat sink, plus this solution would use much less power at 20w and occupy much less space in my proofing box.