Coffee Data Science
Speeding Up Coffee Sifting
Protocol changes to speed up sifting
I’ve sifted a lot of coffee for staccato espresso, and I’ve worked to improve the efficiency of sifting. I currently use the Fellow Shimmy to sift fine (< 300um) and the Kruve Sifter to the coarser grinds by 500um. It takes a few minutes, but I’m always looking for ways to make it faster.
I’ve been able to improve the sifting time of the Kruve sifter using an agitator, and I’ve been able to improve the Fellow Shimmy by dumping the fines into another bowl a few times during sifting.
Improving the Kruve Sifter
I started out with the Kruve sifter, and initially, it sifted at 3g/minute through 2 screens (400um/500um), so it would take 7 minutes or longer to sift 21g. With agitators, I could improve that to 5 minutes. The downside of agitators is that they degrade over time and are loud.
I usually made a paper triangle with a few washed quarters inside for weight to help push down the coffee ground against the screen. I would also use a little Elmer’s glue to seal the paper so that coffee grounds wouldn’t go inside.
However, the paper slowly gets worn down over time.
I experimented with using a tiny wire and a metal disk (an old shower screen from a lever machine). This was effective for an agitator but the wire would snap relatively easily. They could make a screen with a built in spinner. This is much more important for 400um screens and below.
My hack didn’t last long, but I suspect someone will make something better.
The agitator I’ve been working with lately is a metal mesh bent so that it doesn’t it the sides of the sifter too hard. It doesn’t degrade like paper, and it doesn’t make too much noise during sifting compared to a heavier metal disk.
Improving the Fellow Shimmy
I started sifting the fine layer using the Shimmy because it was more ergonomical. It was slightly faster, but more importantly, it took less effort in terms of arm movement. Additionally, it was not as loud and didn’t require agitator maintenance.
It typically takes me 5 minutes to sift with the Shimmy plus another minute to use the Kruve to split the coarse grounds using the 500um screen. Then I found a neat trick where I regularly dump the grinds. If I dump the fines into another bowl every minute, I can cut the sifting time from 5 minutes to 3 minutes.
Part of the gain is due to when shaking the sifter up and down, particles can go back and forth through the screen which slows down the rate at which fines are being separated from coarse particles.
Protocol:
Repeat until sifted:
- Sift for 1 minute
- Dump bottom tray
- Repeat
Then I weigh it at the end and prepare the puck.
Finally, I can have that good staccato espresso shot.
One of the things that gets me about staccato shots is how beautiful the staccato puck is after the shot.
A better Shimmy design would have the fines fall into a cavity that is harder to allow the grounds to come back up towards the screen while shaking the sifter.
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