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While there are relatively cost-efficient solutions to measure and log temperatures during roasting, all available options to classify the resulting roast color seem to be out of reach for most smaller roasting facilities. We were asked for an automated alternative to the rather complex and inaccurate visual classification method based on a series of standardized color disks or the high-priced, laboratory-type measurement devices.

One day, Marko (the developer of the open-source roast logger Artisan) and Paul (a Human-Computer-Interface expert) came across an affordable true color sensor board and immediately ordered some samples. The evening they arrived one was connected to an Arduino and put into an Ikea box together with some quickly assembled LEGO construction to hold the coffee sample. Already that simple device was able to differentiate the presented roasts by color.


We were guided by a series of design principles to turn our initial prototype into a product.

robust & easy to use
small footprint & small sample size
low price despite small scale production
open-source software & hardware
low-energy design, & reuse of standard parts the user most-likely already has (power supply, espresso basket, ...)

Tonino color meter


Early 2014 we launched our first Tonino. To minimize production costs, we used, where possible, tools and materials that were readily available in small quantities. The case combined a 3D printed sensor cover with a recycled can. The only custom part we had to outsource, using expensive injection molding, was the top cover.


Despite its clever design, we found a number of ways to improve our product thanks to new electronic modules becoming available. Our new Tonino features a bright OLED color display and wireless operation, using components from the startup TinyCircuits (Ohio, USA). All in a tiny package!

Respecting our design principles, we decided to realize the wireless charging base, using a novel innovative material from Germany. Kraftplex is a fully organic material, certified as safe even for children's toys standards. It is 100% cellulose, made from sustainably cultivated stocks of softwood, using only water, pressure and heat. No chemical additives, bleaches or binding agents are used in its production. We use a precision laser-cutting process by which we can put together all parts of our base without using any glue or additional screws.

Tuna cans on small truck in Sicily

We would like to thank Sonia, Çetin, Jürgen, Ralf and Rami for their support!