Sciencing the shit out of coffee roasting.

If at first you don’t succeed, iterate iterate iterate again. Coffee roasting is a particularly tricky tradecraft to learn about. Initially there is a lot of reading and documentation and it all seems so simple, so easy. Then the first attempt happens and there is failure. Next, catalog all the data from the first round about and decide to throw away the process because it is flawed from the get go. This leads in to a new process, inherently there is improvement but it is far from a success. Again catalog the data inspect the results and see where to go. Finally with a modded piece of gear and 10 iterations complete the results are not only acceptable but really quite good.

This is that story.

***deep in the weeds writeup is here https://ridingintraffic.github.io/blog/roaster-info/

Phase 1: the whirly pop and a grille. Burner too hot roast time too short, burning, smoke and horribleness.

Phase 2: Poppery II popcorn popper, stock configuration. Roasted fast no control no adjustments, no longer burnt coffee but not exactly good either.

Phase 3: Take apart the poppery isolate heating coil and blower. Add transformer to blower to not over volt the fan, then add router controller to the heating coil to properly dial the wattage up and down. Now it is fully manual. Now the machine has a learning curve to figure out what temps and times to use.

Phase 4: tuning and science. Start collecting the data. begin with a basic roast profile. 4 minutes at 650 watts then 4 minutes at 800 watts and finish at 1000 watts. Collect ambient air temps collect bean starting weight track the times and the temps of the beans through the various temp stages, finally weigh the beans to calculate roast loss. When comparing this data set to that of a traditional “s curve” plot for how a bean should be roasted something was wrong.

The process was missing that nice slow curve. Even though many internet sources were ignoring the initial drop and just starting the bean roasting from zero. A number of iterations happened and all of them resulted in a similar curve with a very bland flavor profile. The bland flavor was the result of the coffee beans baking instead of roasting. Think of a dried out cupcake instead of a crispy outside and a chewy inside. How does this get fixed? Simple, add a preheat stage to warm up the chamber and shift the roasting to indoors so the ambient air temp it closer to 70 degrees. Increasing the ambient air temp means the lower wattage heat coil can be more subtle and offer a smoother curve. the resulting adjustment looks like this

Success our roast profile now resembles the s curve and the beans come out smelling roasted and delicious! Never ignore your graphs and number despite what the internet says.

**If there is desire for all the schematics and the roast logs from all 10 iterations I can include that, leave a comment below