Coffee Data Science
Understanding the stack
I actually have done lots of tests on the grouphead for the Decent Espresso machine, and I actually have been taking a better have a look at water distribution on the whole. So I wanted to know how the shower screen, water diffuser, and water dispenser operated in how water went into the puck. After all a few of these parts are to facilitate a clean grouphead, but I went after a number of questions:
- Does the shower screen help extraction?
- Does the diffuser help extraction?
I performed this test with 6 month old coffee, which implies the coffee didn’t have any CO2 left or little or no. I then did salami shots and measured TDS.
Total Dissolved Solids (TDS) is measured using a refractometer, and this number combined with the output weight of the shot and the input weight of the coffee is used to find out the share of coffee extracted into the cup, called Extraction Yield (EY).
For a shot profile, I did a flat profile at 90C at a flow of two ml/s. The tip of this profile had an extended slow ramp right down to attempt to avoid sucking coffee grounds up into the grouphead.
For dose, I had to extend the dose to cut back the headspace. I also didn’t understand how far to go, so I modified tamping. I dosed, distributed, and tamped half the grounds first, then I dosed and distributed the second half. I didn’t tamp the second half.
The dearth of a tamp allowed there to be little headspace without knowing the precise minimum. So one could study this a bit more and vary some parameters, but I didn’t. I wanted to achieve some data guided intuition.
I used to be a bit of surprised the shot looked so normal with out a shower screen.
This shot looks pretty typical.
So then I removed the diffuser, and we went for broke.
This shot also looked normal. I used to be expecting major channeling from the side, but once it pressurized, it was the identical.
By way of measurements, there weren’t major differences in extraction yield.
