There are a lot of variables to manage when extracting espresso but at the heart of it all is the desire to consistently produce great tasting espresso. From that a lot of recommendations are derived: 25s shots, distribution techniques, preinfusion, etc. Let's put all of that aside for the moment and consider the components of FLAVOR as the only variables...like a recipe for a mixed drink.
Consider this recipe for espresso:
- 1. the black stuff that comes out of the spout at 0-7s into the extraction
2. the dark brown crema that emits shortly after ingredient 1
3. the lighter crema that emits after ingredient 2
4. the blonde liquid that pours well into the extraction process after most of the solids have already been extracted.
Instead of thinking of extraction time as the rule, think about the taste of ingredient 4 and what it does to your overall shot flavor. Then stop extracting when you see ingredient 4 no matter what has elapsed on the clock. Cross check with the clock to make sure you are in the ballpark (we still need a good grinder setting), but once you have your grinder dialed in, set the clock aside. Do your extractions by eye and I think you will develop a more intuitive sense of how to controll the ingredients in your espresso recipe.