If there's one I've learned about espresso while researching and working at a cafe, it's that there are not absolutes. Any kind of training I've received is only jumping off point.
For instance, one thing I was trained to do was to knock around the portafilter between tamps. This was to get any excess grounds off the edges, and allow for a smoother finish on the following tamps. But after reading this article, I realized that perhaps the knocking step could be elimated, the theory being that it will allow for a fuller extraction. Since knocking around the portafilter will break the seal of espresso along the edges of the filter basket, it gives the water that passes through a path of lesser resistance around the edges. Thus, less water in the ground, less coffee extraction.
Another step I was not trained to do is the removing of old coffee oils from the portafilter between pulling shots. Different companies obviously have different methods, but this one just made sense. I picked it up from some other local baristas, and I feel it has given me cleaner, fresher shots. By simply keeping a dry bar towel on hand, and wiping the portafilter clean and dry (while still keeping it hot), the newly added grounds have a fresh start.
It's analogous to my similar method of always using a clean, chilled milk pitcher for each steam. Like coffee, once milk has been frothed it goes through chemical changes, and allowing this already-frothed milk to infiltrate future processes will not allow for a full, fresh preparation.
It's small details like this that can make the difference between an acceptable and a delicious, complex espresso, and I love discovering new techniques and perspectives.
