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Permalink Reply by Chris on January 26, 2010 at 11:59am

Different machines at different times of year (temp, humidity, etc.) with different water sources and different coffees will act, well, differently. While you may be able to tell what has changed by changes in *your* puck, these may or may not translate to the puck of someone, say, on the coast of Australia (where they will most likely be in a different season from someone on the coast of Lake Erie) using locally sourced water and beans source, blended, and roasted far different;y, even if they are using the exact same machine. Simple settings like pump pressure and P-stat will make two identical machines with identical coffees and identical water sources pull way different shots. The Mano portion of the perfect shot will have to change to make up for those variables, and will likely show up in the puck.
The bottom line of puckology is that you pull shots and change variables based on taste. Then examine the resulting pucks once you've discovered a technique that results in satisfying shots. Satisfying shots that are repeatable, that is. Once you establish the good shots, you can determine (to a degree) what goes wrong with future shots by looking at how the puck differs form your established 'standard.
A layered flaky puck (one that separates into strata, and the top falls off first knock) is probably a donut extraction, under extracted, and will probably taste thin. A soupy puck may be a bit over-extracted, and could indicated too fine of a grind. Or a clogging three-way valve. Notice the use of 'probably' and 'could'. I've had great shots that showed a bit of a puddle in the PF afterward.
Find the technique that makes the shots good, and worry about the puck only if things stray. As one bud is fond of saying, 'Pucks are compost'.

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Permalink Reply by Jason Haeger on January 26, 2010 at 12:36pm

The solidity of the puck is a function of quite a few variables.

Once pressure is released, there is only so much space, and it is taken up by coffee and water. The more coffee there is, the less space there is for water, which results in a dry, cookie-like puck.

Roast profile is a factor as well. I've noticed that, no matter how fresh, the less structurally sound the coffee, the more chance of a wet puck. What does it mean? It means that there is more space available for water to occupy once the pressure is released. Nothing else.

What you SHOULD look for, as has been mentioned, are pits, cracks, holes, inconsistencies, "layers", and so forth. These are signs of improper preparation.

Some coffees like a higher dose. Some coffees like a lower dose. What does that mean? Not a lot, but the results in the "hardness" (or dryness) value of the puck will be different between the two. It's not a bad thing.

The notion that a good espresso should result in a firm puck is the product of a time when updosing was advocated as the norm, and David Schomer "pushed the shit" out of his coffee while dosing. That is, cramming more in by pushing down while distributing.(which he may still do)

It reminds me of the idea that "tapping" the portafilter to settle the grounds was considered regular practice at around the same time.

At a point like this, I feel compelled to lead to the question of this: How much headspace is the ideal headspace? Is there an ideal headspace? Does it depend on the coffee? What does this affect?

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Permalink Reply by Chris on January 26, 2010 at 1:23pm

Jason Haeger said:

How much headspace is the ideal headspace? Is there an ideal headspace? Does it depend on the coffee? What does this affect?

Back to different machines, different coffees, etc. As some coffees almost insist on being updosed, and some could go either way (I've never found one that insisted that it be pulled at a much smaller dose than, 'what the basket asks for', but it could still happen...), I think that headspace, more often than not, is a function of proper dose and proper grind for that coffee. Whatever is left over is headspace.
Some machines, however, are *MUCH* more sensitive to headspace issues than others. I'll get all of my extractions starting on the outer ring of the basket, irregardless of grind or dose, on my Astoria. They will quickly fill in an 'heal' themselves for a nice pull almost all of the time, but if I crowd the headspace to the point where the dry puck is even grazing the dispersion screen screw, it's donut city on the way to the sink.
Elektra's have a reputation for being sensitive to headspace as well.
Just my take on things today. Tomorrow, well, we'll see.

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