The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

"reversed" proofing box

MoonshineSG's picture

"reversed" proofing box

While most people need a warmer environment to ferment & proof the breads,  when outside temperature are, year long, around 30C (86F) a cooler place is what is needed.  A styrofoam box and a peltier module were the base of my project.  After using the "cooler box" my dough seams to have more strength and the bread a much nicer oven spring and blooming...  Here are some pictures. If anyone has wants to buld a similar box and needs a few answers, I'd be glad to provide answers (if I have them)


1. the components (the little white square in the middle is the main character. the rest - supporting actors)

2. proof of concept. It works!!! (red temperature is the enclosure, the black is the cooling element)

3. everything put together in a custom cut acrylic box fixed on top of a large styrofoam box

4. the inside of the styrofoam box

5. final product

6. final product in "production" (variations of +/- 1C from the set temperature)

7. the box can fit about 8 bannetons on 2 layers ...

8. ... or 2 custom cut proofing boards (2 layers)



It was fun building it, lots of fun using it!!!!

Doc.Dough's picture

How about a parts list with your sources?

It is bigger than a personal refrigerator, holds enough dough for a family, and should work in anyplace that has reliable power.

How long does it take to cool down and stabilize with your normal load?

MoonshineSG's picture

The list of components and sources:

- 231W 15.4V/15A Peltier module - ebay (china)

- 15V/15A power source - local electronics shop - one of the most expensive parts of the whole project

- 12V power source - local electronics shop - a wall charger with removed cover

- DC/DC Solid State Relay - local electronics shop - second most expensive part

- heat sink with fan for SSR - local electronics shop

- 2 x12” fans (Scythe Gentle Typhoon) - local computer shop

- heat sink for peltier module - local computer shop - any CPU heat sink will do. Some come with fan so you don’t need to get two (above)

- aluminium heat sink (for the cold part of the Peltier module) - ebay (HK)- 30cm x14cm (cut to 14x14cm)

- temperature sensor - ebay (HK)

- peltier module controller - ebay (China)

- Arctic MX4 thermal paste - local computer shop 

- mica plates for thermal insulation - ebay (HK)

- power switch, plug and cord - local electronics shop

- custom plexiglas box, rubber gasket, internal plexiglas shelve and wooden proofing boards - local laser cutting shop based on my own specifications

- styrofoam box - local fishing shop

- wires and screws - local electronics shop

I have not indicate the prices as those might vary form shop to shop. I spent around US$200 (!!).  I know that is not a cheap thing to build, but I couldn't think of any alternative.  The good thing is that the impact on my brad quality is huge.  Before this, with the exception of ciabbata, anything else was barely acceptable. Once I started using the box,  my bread has a much more opened crumb and the oven spring has probably doubled... Now baguettes are like baguettes should be!

As I use a relatively powerful Peltier module (231W) the initial cooling time is around 20-30 min and it takes less than 15 min to stabilise once I put in my dough (either for fermentation in a bowl or shaped for proofing) 

Probably I could have use a smaller box (with a smaller Peltier module and a cheaper power source) for daily use, but occasionally I intend to bake for friends/party so that would require larger quantities of dough to be prepared. 



rossnroller's picture

My place of residence, Perth, Western Australia, is not as warm as Singapore year-round, but much hotter during a lot of the summer. It's a muggy 35C or so today, and we have just had a heatwave where it was 40C+ for days on end (felt like weeks). This can go on well into March, and even in April we can get mid-30s days. So, for several months per year bread making is not terribly easy or pleasant.

I made a SD bread on one of the 40C days last week, and it was 35C in the kitchen during the bulk proof (at night!). I had to reduce the BP to 1.5 hours (next time at these temps, I'll reduce it still further to 1 hour!),  and retard in the fridge immediately after shaping, and it was still a bit wonky - somewhat overproofed, but also with some signs of gluten underdevelopment! Still tasted nice, but not as good as in more moderate bulk-proof temps. At 35C+ I just don't think our yeastie friends function all that well. Can't say I blame them!

I have often wondered about a "reversed" proofing box for summer, and yours is the first I've come across. I'm not confident enough with the technicals to put one together for myself, unfortunately, so I'll just have to struggle through on the very hot days, making whatever adjustments I can. I've thought of experimenting with doing the entire BP in the fridge, as well as the FP, but have been loathe to go ahead with this because I hate the thought of  having to toss the dough due to a failed experiment. Adventurous, aren't I?

Anyway, good on ya for putting your electrical and technical knowledge to such good effect as a baker! I'm envious.


Doc.Dough's picture

Thanks for the detail. That gives me something to work from.  It is a big Peltier module, but you need it to get the initial cooldown.  You could probably use a 20 amp automotive battery charger as a power supply since the Peltier doesn't care much about ripple and everything else is running on regulated 12V.  Might be less expensive, but maybe not, depends on what you can find in the garage, the junk box, and at the local swap meet.

One more question - is the controller a PID type or just bang/bang on thresholded temp sensor output with or without hysteresis?

MoonshineSG's picture

The controller is a on/off type. This is the exact model

Alan Tan's picture
Alan Tan

I know this thread is 2 years old, but I can’t help reading it again and again.

I live in Singapore and I was searching for a way to make a proofing box that can control temperature from a few degrees to 28OC (for reasons already discussed).  I considered a few options:

1. Modify a bar fridge (compressor type), so that it can be controlled by a temperature controller.

2. Buy a thermoelectric mini fridge (unfortunately, most available in the market are too small to be useful).

3. Make a proofer with Peltier cooler, like you did in this project.  

Option 3 is my first choice, but I probably would not need such a big cooler as I am aiming for max of two loaves.  I joined the Forum only today (though I have been using it for a while) in the hope to have a better understanding of your innovation.

Few questions, if you don’t mind:

1. Is the SRS meant for the 15A Peltier? What is the output contact rating of your temperature controller (I am thinking of a direct control using a smaller module)? 

2. Why is the “peltier controller” required?  Can’t the temperature controller do the job directly (simple ON/OFF, no hysteresis)?   The link you posted for the controller is no longer available.

3. Your Temperature sensor look like a STC-1000 sensor I found on the web. Is this the module?

4. what’s the use of the second thermometer?

I have not played with electronics for many years. Would really appreciate your input to help me build something similar.

MoonshineSG's picture

The peltiers are power hungry beasts, so I doubt the controler can handle it directly. In my case there was a voltage difference as well. Controller is 12V while the peltiers is 15V. I don't know the exact model right now but next week I'm back home and I van check. 


I actually have have all the modules for a second small box I intended to build for a friend which since has gave up baking. If u're interested, I'll dig out the receipts with prices....

In any case if u have other questions let me know and I'll try to answer them.