Brewed Coffee Methids: Grind Size - Quantitative Targets


(Eric Zarakov) #1

Hello!

I am trying to find a guild / table that indicates - measured - recommended coffee ground particle size targets ( sizes measured in microns ) for different brewing methods and filter types : AeroPress, Chemex, French Press, V60, etc. I have seen visual guides published with coins as a comparison, but no one seems to have published a thorough recommendation table with measured sizes.

“Consumer” products like the new Rafino sieves offer the ability to measure grind size in microns within the affordable price range for consumers and small businesses.

I know “ideal size” is subject to the chain of other variables - humidity of the beans, varietal, extraction time, water temp, etc. However - I believe a table indicating approximate targets for each method is never-the-less useful as a starting point. I would imagine each type of paper filter ( Chemex, Hario, AeroPress, Melita, … ) and metal filters have material densities that establish a recommended range. Each method has its particular impact on extraction time. Granted - each barista will adjust on their own experience and knowledge.

I live in Guatemala and the practice that I see here for small coffee chains that roast their own coffee is that they do test grinds with their coffee, prepare sample standardized brews and test the results via TDS. Depending on the batch of roasted coffee, they adjust bulk grind size up or down to optimize TDS. Makes sense if you can afford a TDS meter, but still leaves the grind size as a qualitative variable ( not measured)

A TDS meter is out of the reach of most people. A quantitative based micron sieve is becoming available.

Can anyone point me to a table of recommended measured particle size targets for different brew methods?

Look forward to the discussions and perspective!


(Fred Cederstrom) #2

Bump for curiosity. I too would be interested in this information.


(Mark Burness) #3

The problem with the OP’s request is that for any brew method, there is a range of grind sizes that work. Often, as brews by the same method get bigger, the grind can get coarser.

That said, there are some datums. SCAA drip grind is centred around 830um with 65% falling between 596 & 1186um ASTM sieves with 5min of shaking. This specification seems based on the earlier US DoC drip grind spec from before auto drip brewers existed, so this would be a reasonable start point for manual drip, smaller brews might need lots of pulses of brew water to stretch the brew out. If you want to make small brews with one filling pour after pre-wet, then you’re likely going to need to go finer.

ECBC drip grind is finer, centred around 600um.

SCAA cupping grind & Agtron dovetail around 700um average grind size. For light roasts you might try even finer, even for French press. Whereas a large, double walled French press will retain heat better & can take a coarser grind.

I would view all these as reference within a workable range.

A single 600um ASTM sieve, manually shaken, could be useful for a rough, comparative guide to manual brewed methods (~18% passing through for SCAA drip, ~50% passing through for ECBC), in fact this was a proposal made by E.E. Lockhart when he worked at the CBI.

MPE Chicago also have some useful downloads available from their website. Like this one: https://www.mpechicago.com/sites/default/files/resource-library/ground_coffee_analysisa.pdf

Kruve (was Rafino) doesn’t quite give the same results as wire mesh sifting, nevertheless, it is repeatable & useful. The finest brewed coffee grinds I might use (Aeropress, small drip brews with a single pour, small glass French press) will be around 25% of a 10g test grind passing through the 400 sieve with 2minutes of side to side shaking & occasional taps. A friend & I sifted grinds from a bunch of home grinders & found that for a pulse poured V60 brew of 225g to 250g brew water (60g/L) our grounds typically let 13% +/-3% of a 10g test grind pass through the 400 Kruve sieve, achieving mid-box extractions.

I use this grind setting (13% at 400Kruve) with Melitta 102, Bartlett 2 cup (like a Melitta but 3 holes), Kalita Wave & V60, all 13.5g to 225g brew water. I get similar levels of extraction by changing the number of pulses & timing of pulses. (Bloom & 6 pours of ~35g every 20s for V60, 3 pours of ~65g every 40s for Kalita Wave, bloom & 3 pours of ~65g every 20s for Melitta 102).

A coarse grind (still a sub-litre manual drip brew) might be 5% +/-2% passing through the 400 Kruve.

A refractometer is an expensive bit of kit, no doubt, but then so are large ASTM sieves (about £100 each where I live, not much less for 3" sieves). A set of sieves and a shaking machine runs into thousands and is loud. Small sieves can clog easily if you put too much coffee in them. I’d suggest using about 1g of coffee per sq. inch of mesh.

.