For a Good Puck
May 10, 2015
Have you ever had your coffee-making analysed by someone who sticks their fingers in your spent pucks?
Have you ever decided not to use a particular espresso basket or recipe because the grinds are sloppy after brewing?
If you’ve answered yes to any of these, this post is for you.
You can stop worrying about sloppy, soggy, watery pucks because there’s nothing wrong!
Brewing espresso requires water. This water comes at the coffee from above: through the boiler, group head and finally shower screen before it drops onto the grinds. When you engage the pump, this water fills up the space between the coffee and shower screen, then starts to enter and move through the coffee.
At this stage, there’s water everywhere: above the coffee, within the coffee and below the coffee. When you stop the pump, a valve back inside the machine opens up to release the pressure. Water doesn’t really compress under pressure so there’s not much that escapes at that point. Instead of escaping the group head, it just sits on top of and within the coffee grinds. There’s no pressure to force it out of the basket, there’s nothing to push it up and out of the group head. It’s just hanging in the basket with the coffee.
If you pull the handle out really quickly post-extraction you’ll find a puddle of water that’s slowly lowering into the coffee grinds. After a few seconds the coffee has absorbed all of the water.
The larger the gap between your coffee grinds and the shower screen (headspace), the more water there is. The more water there is, the wetter and sloppier your coffee grinds will be.
If there's less coffee and more water, it'll be wetter.
If there's more coffee and less water, it'll be dryer.
VST baskets (which I highly recommend) are taller than most. This is a good thing because it reduces the chances of your coffee grinds butting up against the shower screen. If your coffee grinds touch the shower screen, your extraction will be less even. There should be a gap between the screen and coffee grinds to allow water to flow evenly. A wet puck is a far lesser evil than an uneven extraction!
I’m glad we could clear that up.
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