The Fellow Shimmy Sifter: A Data Driven Review | by Robert McKeon Aloe | Towards Data Science

Oct 16, 2024

Robert McKeon Aloe

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Santa Claus (Mom) brought me a Fellow Shimmy, and I was excited. I wanted to see how good of a tool it was especially compared to the Kruve Sifter. I love sifters, and I think they have a lot of utility especially for espresso. Many people have reviewed the Shimmy online, and I’m reviewing the Shimmy from a data perspective to better understand its utility.

The Shimmy is supposed to remove fines from coffee, particularly for pour-over so that the coffee flows better. The user is then supposed to throw those fines away. I think this is a mistake caused by a misunderstanding of the source of fines.

Previously, I looked at fines from coarse grounds, and they taste much different than fines from finer ground coffee. I theorized the fines from a coarse ground coffee come from the inside of the coffee bean because that part is softer and turns to dust much more easily.

So by throwing out those fines, you are removing a component of the coffee flavor. That doesn’t make the Shimmy an ineffective tool, rather its true purpose has not been realized, which is a tool for staccato coffee. Layered coffee doesn’t have to be relegated to only espresso.

All the reviews I found focused on its performance as an experience and the effects on the taste of coffee as well as commentary on throwing out some coffee grounds.

In terms of sifting time, I can sift with relative easy in 3 to 5 minutes. It is faster for a single screen than Kruve is for 2 screens, and I think it’s design is superior because it is a more natural motion to go up and down rather than side to side. To achieve the same time with a similar screen size with Kruve, I have to also include an agitator which takes away from the experience.

More recently, I have been sifting first with the Shimmy, and then I do a quick sift using a larger sieve on the Kruve to get three layers for staccato espresso.

The Shimmy says that it filters out particles less than 200um in diameter. However, this is a miscalculation.

When I first started sifting with it, I noticed I was getting close to the sift output as my 300um Kruve screen. So I got out my cheap microscope, and the shape of the holes is not circular like the Kruve. They are almost square which means the diagonal is the true sifting ability.

Shimmy Effective Hole Diameter = 282 um = sqrt(2)*200um

I compare the two here:

This is a rough showing. Let’s look closer. I used some image processing to analyze the hole size of the sifter.

These images show the hole measurements colorized where blue is small and yellow is larger. It shows variation in hole sizes and how they aren’t quite random. I have a similar analysis for the Kruve.

This measurement was more challenging because the filter is not flat unlike the Kruve filter. If we assume the hole size average is 282um in diameter, assuming the diagonal, we can use these relative numbers to assess the standard deviation of hole sizes.

From the wider field of view image, the standard deviation would be 85um, and for the zoomed-in image, it would be 57um. This compares with the 300um Kruve screen which has a 113um standard deviation. This result should be taken with a grain of salt because unless I unwrap the Shimmy screen, I can’t accurately measure the whole thing as I can not lay it flat.

I have used the Shimmy to dial in a grind. I know from my past experiments with Staccato espresso that about half the particles are less than 300um in diameter. It doesn’t matter what this is for someone as long as they can measure it. My target is 10g for 24g of coffee.

So, grind, sift, measure, change grind settings if there aren’t enough fine grounds. By the end of this procedure with just one shot of coffee, you should be very close to the best dialed-in shot with minor adjustments. Regrinding coffee will make a few more fines than normal, but you will be much closer to the ball park. You may be able to use a target weight that takes the regrinding into account.

Espresso Machine: Kim Express

Coffee Grinder: Niche Zero

Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)

Shot Preparation: Staccato and Inside-Out Staccato

Pre-infusion: Long, ~25 seconds

Infusion: Pressure Pulsing

Filter Basket: 20g VST

Other Equipment: Atago TDS Meter, Acaia Pyxis Scale, Kruve Sifter

I use two metrics for evaluating the differences between techniques: Final Score and Coffee Extraction.

Final score is the average of a scorecard of 7 metrics (Sharp, Rich, Syrup, Sweet, Sour, Bitter, and Aftertaste). These scores were subjective, of course, but they were calibrated to my tastes and helped me improve my shots. There is some variation in the scores. My aim was to be consistent for each metric, but some times the granularity was difficult.

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 determine the percentage of coffee extracted into the cup, called Extraction Yield (EY).

Intensity Radius (IR) is defined as the radius from the origin on a control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot performance across output yield or brew ratio.

First, I don’t mean to say Shimmy’s value is exclusively tied to how it performs compared to the Kruve sifter. With Kruve, I always use 3 layered staccato shots because they are natural from the sifter. For the Shimmy, I usually did two layer staccato shots because it was more natural.

I think staccato espresso made from either will be better than regular espresso shots, and the Shimmy is easier to travel with. The Shimmy gets close to the same performance as the Kruve but not quite there.

They are close in EY, but there are some fluctuations with taste. In terms of time, the shots with the Shimmy cover the filter faster because the top layer isn’t separated.

The taste score had differences on average which were statistically significant, but the TDS and EY were not statistically different.

Using a sifter can be messy because coffee doesn’t behave. The most challenging aspect of the Shimmy is getting the fines out without a mess, but the coarse particles come out very cleanly. As compared to the Kruve, I use a brush, and it is messier than the Shimmy. I’m used to this, and to me, the mess caused by sifted coffee preparation is worth the taste.

I hope people who have a Shimmy try staccato considering the ease of use. I also hope the people who do pourover, try a form of staccato using the Shimmy rather than throwing it away. I also hope cafes could use the tool or Kruve’s sifter to dial in new roasts with less waste.

For me, I’ve been using both the Kruve and the Shimmy. Often, I use the Shimmy first, and I then put the coarse grounds through a 500um screen in the Kruve.

If you like, follow me on Twitter, YouTube, and Instagram where I post videos of espresso shots on different machines and espresso related stuff. You can also find me on LinkedIn. You can also follow me on Medium and Subscribe.

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