If my espresso shot appears to be extracting too quickly, what factors could be causing this? What should I change to try to get a better result?
Without more details, it's hard to pinpoint, but here's a few suggestions:
Start by checking the setting on your grinder. You may not have it set fine enough for espresso. NOTE: if the coffee is really stale, as in many months old, the shot will start blonding early.
How much are you dosing? If it's too low you can get channeling and fast extraction (we tend to use 17-21 g depending on the beans). Also take into account the size of the portafilter basket. For example, if you try to put 17 grams of coffee into a triple basket, you will never get a good pour. I would suggest trying 18 g in a double basket and see if you notice an improvement. You should shoot for roughly a 25 second extraction.
Double check how you are distributing the coffee in the portafilter. If you are tamping unevenly, the grinds will be more likely to cause channeling with an uneven shot (check out the WDT method to help ensure proper distribution).
Otherwise, make sure you're fully engaging the portafilter into the grouphead and it is not loose when pulling the shot.
This can be due to a few factors:
The "formula" tends to be:
~20g coffee grounds + 24-27 sec of water == ~30mL (~30g) of coffee.