Just Pucker

Next time you pull an espresso, take a look at your "wet puck" - it's another indicator you can go by when assessing whether the extraction is doing the coffee justice - check out the following entry on the coffeemumbojumbo website for more insight into the subject and lots of photos to illustrate the points :

http://www.coffeemumbojumbo.com/2012/10/15/perfect-coffee-puck-of-an-espresso-extraction/