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How to make IoT an ingredient of your sourdough

Published in Design, Technology

Written by

Annika Madejska
Senior Designer

Annika Madejska is a Senior Designer at Nitor who has a thing for tackling complex design problems and who loves to push herself outside of the comfort zone. She carries a torch for ethical technology, especially AI driven services. In her spare time, she kicks back with some gardening, painting or textile arts.


November 2, 2020 · 6 min read time

Like so many others, I got a whole range of new hobbies during the pandemic. We now have plenty of woolen socks, a remade vegetable garden, and a crocheted granny square blanket that is well on its way. But mostly, we have jars filled with bubbling sourdough in the kitchen. And as it turns out, finding out when the sourdough is ready to bake with is the hardest part for beginners. So I decided to solve this problem by introducing IoT and microcomputers into my baking experiments.

As a UX designer working on screen-based user interfaces, it is sometimes nice to break away from the daily pixel-pushing and create something tangible. It’s good to be versatile and capable of working with physical objects and spaces too – and I find it very useful to be able to do physical sketches using some degree of technology.

It gives you great insight into what kind of problems you have to solve to make your idea work and an understanding of how things work underneath the hood. Sketching on paper or with a prototyping tool won’t show you the actual physical issues you need to figure out. For example, when I started solving how the sensors would attach to the jar outside, I realised that there might be a gap in between the strip with sensors and the jar. The extra space would let in light and topple my plans.

Making sure the sensors are snugly fit to the jar became a problem I needed to resolve. But back to the hardware in a while. First, there are a few things you need to know about sourdough.

Annika's blog – sourdough & IoT

Examples of physical sketches incorporating some degree of technology.

Sourdough has a personality

A sourdough starter is a microbiota made up of flour, water, and (amongst other things) lactic acid bacteria. The starter is the bit of sourdough you keep after each bake – you always save a small piece (most keep it in the fridge) and use that as a starter for the next time. 

It turns out that about 26 percent of a sourdough starter has unique bacteria that can be traced to the baker's hands and the water used to get the sourdough going. The rest comes from the flour. This microbiota also affects the taste of your bread. The fact that sourdoughs contain different microbes also means that each sourdough behaves slightly differently when it comes to the fermentation process. 

Most people in the cult of sourdough baking give their sourdoughs a name. And they talk about the dough as if it has a personality. (I have two sourdough starters. One is called Buffy, and the other one is called Spike. Spike is a wheat sourdough while Buffy is rye-based.)

Once you have a well-working sourdough starter, you" feed" it flour and water, which then kickstarts the fermentation and makes the sourdough rise. On some days, everything works as planned. Sometimes nothing seems to work. Things like temperature, humidity, and weather all affect your sourdough starter. So you don't just need flour and water, but also lots of patience.

Those that have had their sourdoughs for a long time know it well. They can quickly determine if there is enough fermentation power in the jar to be used for baking.

The tips for beginners to decipher this are many: 

  • Look at the surface – it should have a certain type of bubbles. 

  • Put a disposable latex glove over the jar's top – when it rises from being full of gas, the dough is ready for use. 

  • Look at the dough through the side of your jar – does it have bubbles of different sizes? 

  • Take a small bit of the sourdough and drop it in a glass of water – if it floats, you can bake.

However, the most frequently mentioned method is the dough size – if it's doubled, it's ready for baking. Now it is time to get back to the hardware

Annika's blog sourdough & Iot: arduino

Sketches with cardboard, Arduino Uno, and a glass jar.

The idea takes physical form

When bringing out my Arduino Uno and Raspberry Pi 4B, it was this last method I had in mind to prototype for – to measure the increase in volume somehow.

Another criteria I used as a constraint was that all the electronics had to fit on the outside. When a sourdough ferments, it sometimes gets a bit too happy and overflows the jar. I wanted to avoid having to wash the parts that would contain the electronics.

After some tests with the glass jar and a piece of cardboard, I had an idea. I would give the sourdough a personality by giving it a voice. 

Photoresistors would trigger the voice feedback. Additional visual feedback would come from an LED diode lighting up when the rising sourdough covers the photoresistor.

In case the sourdough would rise more than expected, I added a placeholder ”mouth” on my physical sketch that would symbolize an outlet of any overflow from the jar. I did two separate tests, one with an Arduino and one with a Raspberry Pi, as I wanted to compare the workflow.

Annika's blog – sourdough & IoT

My circuits and some creative mess while doing physical sketches.

Putting it all together

As a beginner – once you have an idea, you can search for Arduino and Raspberry projects online that match your area of interest. 

And this is a great thing for a designer who isn’t very well versed in coding and making circuits: you don’t need a very advanced project to sketch a possible IoT item. 

It’s all about putting the existing projects into context. For Raspberry Pi, I used the following project as the base for my experiment. However – this project has faults in the illustration of the circuit, and the most crucial change is to make sure you get the right voltage from the Raspberry Pi (3.3 V).

This problem nicely illustrates one of the hurdles you have to overcome as a beginner of circuit tinkering: mistakes might fry the hardware. I genuinely recommend reading up on circuit creation basics if you’ve never played around with them. Start from simple projects and build them straight from the instructions just to learn the basics.

You can also use Tinkercad to build virtual circuits to test if they work as intended. My project was simple – but if I hadn’t already had a few other practice projects under my belt, I would never have been able to see that something was wrong in the illustration of the circuit. 

So what did I learn from this project? A lot about photoresistors for sure! To actually make my idea a reality, I would have needed an advanced version of photoresistors that are more sensitive to dimmed lights indoors. But the idea on its own did work. 

And it would be entirely possible to connect the sourdough jar to a speaker and an app – and construct a UI where you could select a personality for your sourdough. The jar could even send push notifications of any activity to the phone – not only use the voice feedback that requires you to be in the room with the jar to hear it.

I also learned how fun it is to take a simple circuit and create a concept around it. Refining a tangible user interface was a nice contrast to my daily work with screen-based software.

Finally, I learned that putting what I felt was a silly and somewhat childish project in front of my colleagues at work was not embarrassing. On the contrary – it sparked interest and more innovation.

Written by

Annika Madejska
Senior Designer

Annika Madejska is a Senior Designer at Nitor who has a thing for tackling complex design problems and who loves to push herself outside of the comfort zone. She carries a torch for ethical technology, especially AI driven services. In her spare time, she kicks back with some gardening, painting or textile arts.