Have You Ever Analyzed Your Coffee by Digging into Used Pucks with Your Fingers?
Have you ever decided to change your portafilter basket or espresso recipe because your used pucks felt slippery?
If you answered yes to at least one of these questions, this post is for you.
You can stop worrying about slippery, wet, and watery pucks, because there is nothing wrong with them.
To make espresso, you need water. It comes from above: from the boiler, through the group head and the dispersion screen, and down to the ground coffee. When you activate the pump, the water first fills the space between the coffee puck and the dispersion screen, and then it starts entering the puck and moving through it.
At this stage, water is everywhere: above the coffee, inside the coffee, and below the coffee. When you stop the pump, the solenoid valve inside the machine opens to release the pressure (which is why some water is drawn back into the group head and the heat exchanger). Water doesn’t compress much under pressure, so not much of it exits through the group head—it simply remains above and inside the puck. There is no longer any pressure pushing it out through the bottom of the portafilter or pulling it back up. It just stays trapped in the basket together with the coffee.
If you remove the portafilter very quickly after the shot, you’ll see a small pool of water that will slowly be absorbed into the puck. Within a few seconds, the coffee will absorb all of the water completely.
The larger the space between your coffee and the dispersion screen, the more water will remain there. The more water there is, the wetter and more watery your puck will be.
VST baskets (which I highly recommend) are taller than most other baskets. This is a good thing: it makes it less likely for the puck to touch the dispersion screen. If the puck touches the screen, extraction will be less even. There should be space between the screen and the puck to allow water to flow evenly. A wet puck is a much smaller problem than uneven extraction.
I’m glad we’ve finally cleared this up once and for all. ☕
