Making outstanding coffee is alchemy is as much art as science.
There are countless variables: the barista, their technique, the machine, grinder, humidity, air temperature, grind-setting, temperature and pressure of the water. And the beans, of course — how recently they’ve been roasted, the wash method, country of origin and how they’re blended together to meet milk.
But so much of that is invisible. You see your friendly inked, bearded barista and need to know: can I trust the coffee he’s making?
My rule of thumb is this: a good barista cares about the product they make and coffee buffs vote with their feet and wallet.
So here’s my method to discern the good barista from the bad: watch the tamp.
Wot’s that then?
This is a coffee tamper. It compresses the coffee grounds within the group head (the thing at the end of a handle that holds the coffee grounds). Not every person behind a coffee machine knows now to use a tamper correctly.
Water needs to go through the coffee grounds at extremely high pressure (more or less 9 bar, which is nine times the atmospheric pressure at sea level). That means the coffee grounds needs to be compressed as much, and as evenly as humanly possible in order to generate a beautiful creamy crema.
So watch your barista. Look for a right angle with their elbows, pushing down firmly and evenly. Make sure they tamp with their full body weight. Make sure they understand something about the science of brewing coffee. If they don’t, approach with suspicion, and don’t be surprised if their coffee is weak, bitter, or unpleasant.
Bonus: The Sweep
If you have a keen eye, you can try to watch for the sweep. The sweep is the action of distributing coffee grounds before tamping. Some excellent baristas will use a tool but you may see others looking like they’re quickly polishing top coffee grounds. This is called the Stockfleth’s Move, which is passed around from coffee nerd to coffee nerd, and is now over the internet.
Watch master barista Tim Wendelboe (2005 World Barista Champion) demonstrate Stockfleth’s Move here:
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