Uneven Puck Saturation?

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#1: Post by Jnash »

I've been examining my pucks post-brew, and notice that the outer sections or layers of the puck seem to be more saturated (and thus presumably more extracted) than the inner portion of the puck. This outer portion (top, bottom, and along basket walls) looks darker and seems wetter than the interior of the puck. Does this seem normal? It almost seems to me less water under pressure is getting to the interior of the puck. It's not dry - it just looks lighter, feels a bit less wet, and seems possibly less saturated than the outer areas.

I'm using a Gaggia Classic Evo Pro and DF64 Gen II grinder. Dosing a medium roast coffee at 18 grams, with around 36 out, and shot times bouncing around the 30 second mark. I WDT, and get obvious channeling infrequently. I pre-infuse manually around 6-8 seconds. I'm pretty happy with the resultant taste, but wondering about this. Do most or all pucks look something like this post brew? I halfway wonder if I'm not getting the full 9 bar rated pressure of the machine. Or maybe try to pre-infuse longer?

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#2: Post by erik82 »

Look up puckology. Short answer it's completely useless to look at your puck and try to derive any conclusion fomr it about extraction. Only way to do this is using a naked portafilter.

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#3: Post by John49 »

Jeff, the dark ring that you noticed is due to a lack of flow in those regions of the puck. A basket with perforations that do not extend to the outer wall is responsible for this effect. A paper filter on the bottom would slightly mitigate this. There are many baskets now that have perforations that extend closer to the wall. As an example, I used a Reneka micro sieve basket with 19g of coffee, for years, and also saw this dark ring in the puck. With a VST basket I used 17g, I now use a Weber basket and achieve the same intensity of flavour in my milk drinks with 15-16g of coffee.

Jnash (original poster)
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#4: Post by Jnash (original poster) »

John, Thank you. That's an interesting explanation, and I will look closely at those alternatives. It is true that the baskets I've been using, while of good quality, are not perforated out close to the edge of the basket.

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BaristaBoy E61
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#5: Post by BaristaBoy E61 »

Jnash wrote:Or maybe try to pre-infuse longer?

It's mostly about the preinfusion & grinding.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

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#6: Post by Jeff »

FWIW, The Gaggias aren't known for fantastically uniform water distribution out of the shower. You might try either one of the sintered mesh puck screens or something like the Ikape or MHW-3Bomber ones. Might help, might do little more than help keep the shower screen and above cleaner.