Wednesday 6th of September 2017
I learned a new word this week. Puck. Yes, puck.
Sounds rude, right? Sorry to disappoint, but it’s not rude at all.
In fact I see several pucks every day of my life – and those of you working in the coffee industry probably see hundreds every week. So what is it? Simple. A coffee puck is the little cake of used coffee grinds that you remove from your espresso machine portafilter after you pull a shot.
In an ideal world they’re dry and flat and slip out whole, with a single tap.
But in my experience they’re often wet and sloppy and I need to scrape them out with a spoon.
A key factor is the presence or otherwise of a three-way solenoid valve. Solenoid what? Let’s get technical for a second. In short, all commercial machines have this valve. It controls the flow of water between the boiler and the brewhead – and once your espresso shot has been pulled it helps carry excess water away from the coffee, down into the drip tray.
But – and this is a fairly major but, in my view – many home machines do not have this valve, meaning that excess water simply stays where it is, on top of the puck. Thus we have coffee soup.
There may be other factors too.
If you load the basket with too little coffee then the space between the grinds and the shower screen can fill up with an excess of water. Try loading more coffee and see if that helps.
But beware – overloading the basket is another coffee crime as it doesn’t allow the grinds sufficient room to expand, meaning you could have an uneven extraction.
And of course, the wrong grind size could also add to the problem. A super fine grind is required for espresso but again, home machines sometimes struggle to maintain the pressure required for the perfect shot (see previous article, The Perfect Nine) so as ever, it’s all down to trial and error.
I’ll end with some good news. A wet puck doesn’t automatically mean your coffee will taste bad. Yes, in some cases it indicates you need to work on your technique. But many baristas accept wet pucks as part of life. So long as the shot tastes good, focus on the flavour, not the floods.