Immersion, Percolation, and Grinding-- A Quiz and Contest - a podcast by Scott Rao

Let’s have a quiz and a contest. :)

Suppose you are to make these four brews using similar brewing ratios and a properly aligned EK grinder with settings 1–-11, with 1 being the finest setting, 11 the coarsest.)

• Cupping, to be sampled at 12 minutes

• v60, using 22g grounds and a 3:1 prewet plus one main pour

• French Press, 4:00 brew time

• Fetco, using 120g grounds, 2L of water, an appropriate basket size, 15% prewet, and 4:30 programmed brew time.

The Quiz: 

Easy (easier?) question:

1. Put the brews in order, from finest grind to coarsest grind AND tell me why, other than empirical evidence, you chose that order. 

Bonus question: 

2. Based on a v60 grind of #6, predict the grind settings needed to make all four brews extract to roughly the same percent. 

The reasoning behind the proper grind settings is straightforward, yet I have never been to a cafe that chose the correct order for those grind settings, let alone remotely correct grind-setting numbers for all of them ("correct" meaning settings likely to produce similar extraction %'s for all brews.)  Makes you wonder about the dial-in process at cafes. 

Since most readers seem timid about offering blog comments, I’d like to add an enticement: the first person to get #1 right with the correct reasoning gets a free signed copy of any of my books.  If you already have my books, thank you, and I'll buy you a copy of The World Atlas of Coffee by James Hoffmann, because it's awesome.  If you already have all of those books, I'll find a suitable replacement prize.  

The first person to get both #1 and #2 correct earns a book or the option to receive the first production model of an exciting one-cup brewing gizmo I'm in the process of creating.  (hint: choose this prize.)

Good luck!

 

UPDATE

Over 100 readers took a stab at the quiz. Thanks for writing, for having the guts to take a guess, and for the clear communication. I have high-quality readers!

 
I suppose I'm naive-- I've been asking friends for weeks how to motivate readers to comment on the blog. Now I know: offer them free stuff :)

THE WINNERS ARE.....

QUESTION #1 CAN GENCER!! Great job, Can. Your reasoning was close enough to what I was seeking. For someone who doesn't have an EK, your grind guesses were excellent, as well. I already knew from your prolific blog commenting :) that you have a keen mind.

QUESTION #2 CHRIS CAPELL!!! Judging this was tough. I wanted to be flexible about the numbers, so there was a little judgment involved. And a few readers offered good numbers but hadn't explained their reasons for answer #1.

Chris was the first to get in the ballpark with the numbers and explanation. Congrats Chris!! (full disclosure, Chris worked with me for about a year, circa 2008/9. At least now I know those endless chats about extraction paid off!)

ROSS NICKERSON, GABOR KISS, AND WESTIN MILLS all wrote in with an excellent all-around answers as well. Thank you.

Thanks to everyone for your answers. I'll post all of the comments now and will reply to a few.

QUIZ ANSWERS

FROM FINEST TO COARSEST:

French Press -> Cupping -> V60 -> Batch Brew
*or*
French Press -> v60 -> Cupping -> Batch Brew

This was not a trick- I was willing to accept either order, because measuring the TDS of a cupping is challenging. Whether you stir before sampling and from where in the cup you take the sample have a huge impact on the reading, and it's nearly impossible to trust the reading, as it's too technique-dependent. I measured a cupping this morning and found that depending on whether I agitated the cup, I could get readings of either 1.10 or 1.40. Go figure. Because of this, I wanted to be flexible about where readers put the cupping. Logically, cupping should be coarser than French Press because of the extended contact time in cupping.

THE REASON FOR THE ORDER

Several astute readers noted that percolation (drip) is more efficient than immersion at extraction. (*If a reader wrote "because drip extracts more than immersion" I didn't count that as specific enough--sorry)

Drip is more efficient than immersion primarily because during percolation, strong coffee is being removed from the slurry while fresh, clean water (good solvent) is being added, for most of the process. That keeps the concentration gradient in the slurry much higher for most of a drip brew vs. an immersion. Yes, there are other differences (temperature, amount of convecting of liquid, agitation, etc) but by far the main driver of percolation's superior extraction ability is the higher concentration gradient during much of the brewing process.

Assuming you've read every word of this blog over time (you have, right?), you may remember the discussion about the Ground Control brewer and how repeatedly draining and refreshing the slurry increases extraction a lot.

THE NUMBERS

These numbers are estimates, and I was simply looking for someone to come up with numbers in the ballpark. Depending on the way you sample from a cupping, the alignment of your burrs, etc, these can vary a bit. I was looking for something on the order of

FRENCH PRESS #4--#5
CUPPING #5.5--#7
V60: #6 (it was given)
FETCO: #9.5--#11

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