Puck prep study

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#1: Post by RapidCoffee »

Stéphane Ribes recently posted a puck prep technique study on the (private) Decent Espresso web forum. I believe his findings deserve a wider audience, and he graciously gave me permission to repost them on H-B.
video showing visual uniformity of extractions

slide updated: further testing shows less consistency with no distribution

* Visual uniformity of the extraction was rated in a poll of forum members (using the video without any technique labeling).
* Modified Rao "blooming" extraction profile incorporates a 20s pause after preinfusion.
* The Hog tool introduces an array of small channels into the puck, speeding up "pre"infusion. AFAIK it was first mentioned several years ago in a Perger "teaser" on BH.
* "Raking" the puck is the Decent Espresso term for a partial WDT (only stirring the top 25-50% of the puck). No, it doesn't make sense to me either.

Stéphane is one of the brightest lights on Decent Diaspora. I keep hoping he'll find the time to participate directly on H-B. :-)
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#2: Post by learncoffee »

So, based on the Summary chart, doing nothing is the best option? Minimal effort, no cost, maximum result? :D

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#3: Post by RapidCoffee (original poster) »

learncoffee wrote:So, based on the Summary chart, doing nothing is the best option? Minimal effort, no cost, maximum result? :D
Based on taste results... perhaps. :) Visual uniformity was low but other indications of a good extraction were high.

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#4: Post by Spitz.me »

This is super cool!

From the pictures that I see, it looks like the findings are dependent on achieving a fairly even distribution in the basket prior to tamping. His "no distribution" picture shows that this puck didn't channel so he had even distribution without having to fiddle with the grinds. Right?

It would have been interesting to me to see how channeling affects the outcome because it's the reason why we fiddle with the grinds in the first place. Isn't it?
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#5: Post by yakster »

I bet the modified Rao "blooming" extraction profile incorporating a 20s pause after preinfusion greatly mitigates channeling, probably reducing the need for WDT in these tests.

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#6: Post by RapidCoffee (original poster) »

I agree: good barista + high end gear + long PI + low max pressure (5-6 bar) mitigates the need for additional puck prep.

But it's still a cool study. 8)

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#7: Post by belegnole »

So, would taking it the long preinfusion out make a marked improvement in showing the differences in the methods?
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#8: Post by slipchuck »

I am surprised that the extraction yields are virtually the same

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#9: Post by Peppersass »

It's about time someone tried to do a study of puck prep techniques versus taste, but even though some rigor is evident in the protocol I wonder if it was rigorous enough.

First on my list of questions is, was blind testing used? Seems like it would have been pretty difficult to blind taste 3-5 shots averaged for each technique, and if that was done, how were the taste results averaged?

I'm also a little skeptical that the taste results correlated perfectly with the %EY results. While my own experience has been that there's a general correlation, it's not perfect. And can the author really taste a difference of 0.5% EY? I can't.

I'm wondering whether using a VST basket outside the recommended dose tolerance (+/- 1g) might have affected the results.

In my experience, long slow preinfusion does tend to minimize channeling as long as there aren't any gross distribution or tamping errors.

What is circular motion of the PF? Does that mean the PF was rotated while the grinds dropped into the basket?

A little surprising that the Londinium tool fared relatively poorly. I'd like to see more comparisons with different needle sizes and configurations (like the mini whisk I use.)

For several years I've been gently tapping before tamping. That has made a noticeable difference in channeling reduction and visual appearance.

FWIW, I use the rake method, but only when preparing singles. I use a Tidaka funnel designed for VST 7g baskets, which makes it a lot easier to load and tamp the depression in the basket. But if I WDT all the way to the bottom of the funnel (i.e., contact the perforations in the basket), a little coffee escapes under the edges of the funnel into the upper portion of the basket. Not a big deal, but rather than brushing it back on the puck and retamping I just rake the top 25%-50% of the puck. I haven't seen a visual difference between that and WDT down to the perforations, nor have I tasted any difference.

After WDT, I use my mini-whisk to even the top layer of grounds, and while doing so leave a small depression or divot in the middle of the puck -- i.e., create a slightly concave surface. This has completely eliminated halo extractions. I'm using a flat tamper and have had some thoughts that going back to a convex tamper might have a similar effect.

I use a BT Wedge distribution tool and no tamper when preparing doubles. It would be nice to see that techniques studied.

Finally, does anyone make/sell a Hog? I remember the tease on that but found an opportunity to try one out.

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#10: Post by baldheadracing »

slipchuck wrote:I am surprised that the extraction yields are virtually the same
I'm the opposite - i was surprised at how different the EY was (although we don't know how many shots were pulled for each prep variant).
Same incredibly-light-roasted coffee, same EK, same burrs, same dose, same yield, same machine, same (mostly) pressure and flow profile ...
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada