If you always have perfect distribution, perfectly fresh coffee beans, or a machine with internal pre-infusion or advanced pressure profiling this article is probably not for you.

If you are a mere mortal who sometimes experiences shots that exhibit some channeling or various other errors related to basket prep, here is a simple and quick pre-extraction step that I have been playing with lately on my Linea Mini with good results.

The problem was that in all the covid-19 craziness I stocked up on more roasted beans than I usually would in case there was a shortage later on, and then the reality set in that the longer the beans aged the harder and harder it was to execute a clean extraction with an acceptable flavor.

I had a large kitchen sized water misting bottle, and so I prepared the shot as I normally would, and at the point that I would normally lock the pf into the machine, I misted it a few times with water. Barely a couple of grams of water, evenly sprayed across the surface of the puck, with no visible disruption to the puck. The bottle and the pf were probably 110cm apart during the misting (the pf over the sink).

The results have been 100% positive so far. Instead of regular channeling with the older beans, shots come together in a pretty cone shape within a few seconds, much darker colored liquid during extraction and darker crema in the cup, more complex flavor and mouthfeel.

Anyone else want to have a play and report back?

Ps. Sorry about a new acronym just couldn't resist....

A number of people on the decent espresso forum did this a short while ago with very positive results also, similar effect to putting a filter on top of the puck. From what i can remember 2 g of water and the same characteristics as you describe + some other observable changes such as later blonding. Did not change extraction yield or taste consistently though. They even took some pictures/videos of why it may be effective. Sorry i can't copy all their data and videos maybe some are members here. It's worth playing around with for sure.

I did this on my Robot basket after tamping before I switched to using a a damp filter paper. FWIW, the damp filter paper on top of the puck has worked so effectively on eliminating channeling, and is so easy to rinse off and re-use that I've switched to this method 9 out of 10 times now on both the Robot and the Bianca. It also makes clean up cinch as you don't end up with grounds on the group head / shower screen.

Credit where due:
This method was invented by Stéphane Ribes last November. Here is a picture from his original post:


Stéphane, one of the brightest stars on Decent Diaspora (the Decent Espresso forum), went on to note that "the most (amazing) result of puck spraying is the significant increase in puck resistance".

I have encouraged Stéphane to join H-B and share some of his other interesting observations. Let's hope that he does!

Has anyone compared this to misting the beans before grinding? Same results?

Misting the puck seems to affect (accelerate?) preinfusion. Misting beans before grinding (RDT) reduces static. I don't know how (or if) it impacts the extraction.