Disclaimer: I am not affiliated with Baratza or with Kruve and this post is not sponsored.
There is a wide variety of coffee grinders, and a good (entry-level) one (for home use) is Baratza Encore. Independent of what grinder you have (even if you have one costing a few thousands), there is a problem. The output consistency of the grinder, the size of ground coffee pieces, is a distribution which might be surprisingly wide. As the water extracts solubles from the coffee pieces, it matters a lot the size of these pieces, however there is usually a very limited visibility or control you have on this process.
There is also, I think, another problem that people call specific grind sizes as fine, medium, coarse, which quantitatively does not mean much. Even more, there is no simple way to compare the settings of different grinders, and even the same grinders because even the same model might have a different calibration.
The only accurate way to solve this would be to see particle distribution of ground coffee and select (e.g. by sieving) the range you are interested in. Since this is the only reliable way to achieve the same ground coffee, for example, SCA (Specialty Coffee Association) Grind for Cupping standard says the coffee for cupping “shall be ground so that 70-75 percent of the grinds pass through the 20 mesh sieve”. (Coffee Standards @ SCA)
One way to measure particle distribution is to use laser diffraction particle size distribution analysis. As you might guess, such devices are not for home use. Another approach which can also be used at home would be to use image processing, basically taking a photo of the ground coffee, and using image processing to approximately calculate the distribution. This should work, but it solves only one part of the problem, to understand the particle size distribution, if you want to discard some of the ground coffee particles, you still need a sieve.
Kruve Sifter is a unique product that allows you to sieve ground coffee with a variety of precise sieves and because you can have two sieves at the same time, basically the idea is you can effectively sieve and take the ground coffee having particles in a certain size range (e.g. 400-800 micrometer -um-). Of course it is not the same as seeing a particle size distribution, which would take a long time to test with a single Kruve set, but I think it is more practical. There are also more advanced devices doing this automatically using different sieves, but they are also not for home use.
In order to make a simple test, I bought a cheap coffee (dark roast) from supermarket, and tried different sieves for V60, french press and moka pot as Kruve’s recommendation. The point of this test is not to say anything like they are the best settings since this depends on a lot of other things, and actually after doing this test, I repeated it with the settings I use the most with the grinder.
Kruve recommends 400-800um for V60, 600-1000um for french press and 350-700um for moka pot. So using this coffee, what would be the best setting in my Baratza Encore grinder according to the recommendation of Kruve. I will assume the best setting is the one giving equal fines (smaller particles) and boulders (larger particles) than the actual target, as Kruve recommends.
Baratza Encore recommends setting 15 for V60, 28 for french press. There is no moka pot recommendation, but I assume it would be around 10-12.
The method I followed is:
- Before measurement: I cleaned the grinder cup and the sieves, then run the grinder and adjust the setting while it is running, then waited a few seconds and discarded this to eliminate previous particles inside the grinder.
- Then I run the grinder and measured 10.0gr of ground coffee, and put this into the Kruve sifter (using the specific sieves as indicated below).
- I sieved for 60 seconds.
- Then I measured the weight of ground coffee collected in top, bottom and middle sections of the sifter.
For weight measurements, I used a Kern EMB 2000-2 Precision Balance (readability and repeatability 0.01gr, linearity 0.05gr) which I recently calibrated with a 2kg calibration weight (Mettler Toledo F1).
I did each measurement only once, although they look consistent to me compared to other measurements, no general interpretation should be made using these results.
Each row below corresponds to a specific Kruve sieve, and each column corresponds to an Encore grind size setting. Each measurement (numbers in cells) are grams. The total grams (in a single column) are close to 10.0gr, the small difference from 10.0gr is the ones stucked in the sifter or lost.
Measurement 1 for V60: 400-800um
I think one obvious interpretation is it looks like the best setting above is 8, and this is very out of the recommended setting (15).
Measurement 2 for French Press: 600-1000um
Similar to above, the best setting seems to be 13, but this result is quite bad because there are a lot of smaller and larger particles, so you need to discard a lot if you want to use only the ones between 600-1000. This is also far from the recommended setting (28).
Measurement 3 for Moka Pot: 350-700um
7 looks like the best setting here.
Measurement 4 with another (speciality) coffee for V60
Seeing the first measurement above, this time using another (medium roasted) coffee, I used setting 8. The result was:
- >800um: 4.80gr
- <400um: 0.84gr
- 400-800um: 14.17gr
So it seems like, for this coffee, I should have used even a finer setting than 8 (since % of larger particles > % of smaller particles), which is consistent with the first measurement above but still surprising.
On the other hand, I find the indication of these results, using setting ~8 for the grinder for pour-over resulting a too fine ground, because the brew is both taking longer time than I want and it is too strong, at least for my taste, and I keep going back around setting 12-14. Kruve also has a (manual) tool to judge the grind size (https://www.kruveinc.com/products/brewler), and it is also written on this tool that 500-800um is medium/fine and 800-1100um is medium. So I decided to try also 500um sieve at the bottom and 1100um at the top using the same coffee as in the measurement 1-3 above (also after seeing a few posts related to Kruve sifter on https://markwjburness.wordpress.com/).
According to Kruve’s description for calibrating a grinder, for 500-1100, setting 14 is definitely the correct spot. So actually considering the recommendation of Baratza for pour-over (setting 15), this is actually pretty close. So if I go down from the recommendation it moves the average into medium-fine direction (500-700) and going up takes the average into medium/medium-coarse direction (800-1100, 1100-1400). This probably explains why I find the 400-800um sieves too fine, it is probably too close to being a fine ground coffee.
The photos below are samples from the top, bottom and middle sections of Kruve sifter (with 500um and 1100um sieves) when grind setting 14 is used on Encore. All images are taken at same magnification (2.5x) with Zeiss Stemi 508 Stereo Microscope and Fuji X-T2 Camera. They look like I just zoomed out but they are actually different stacks of ground coffee.
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