There’s no question that the quality of espresso extraction improves a bit every year. There are many factors driving this, including better equipment, and perhaps better baristas but, believe it or not, espresso extraction is also an area where innovation is still happening.
One of the big changes in how baristas think about espresso extraction today is driven by a better understanding of channelling and distribution. Channelling is the phenomenon where water will follow paths of lower resistance more readily than paths of higher resistance in the puck. This is typically caused by clumps or uneven distribution in the ground coffee. It leads to a combination of both over and under extraction. In other words, poor distribution leads to poor espresso extractions through channelling.
The specialty coffee world has come up with lots of approaches to improving distribution and reducing channelling. At the most basic end of the scale, a vigorous tap on the side of the portafilter does have an effect. Grinder chute improvements have also helped. One of the newest and most promising approaches is the use of a Wire Distribution Tool (WDT) known as the Weiss Distribution Technique (also WDT; go figure).
A Wire Distribution Tool (WDT) allows you to break up the clumps in your coffee puck before tamping, by mixing everything around with very fine wires and breaking up clumps. You can think of it almost as if you’re whisking your coffee puck (though please don’t start beating it like it was a bowl of eggs; the effort should be gentle).
There are many WDTs out there, even some manufactured at home, but one of the best ones is this version from Normcore. With ultra-fine, food-grade stainless steel needles (including some spare ones in the box), it’s perfectly designed to help you achieve ideal distribution, reduced channelling and better espresso.