Espresso – 7 variable equation


coffee grounds

Great espresso isn’t automatic – it takes a sharp mind and clear understanding to pull truly great shots.   Why all the big claims?  Well….


Remember high school algebra?  Solving for X was hard enough; then they introduced two variable equations (solve for X and Y; solving for one in relationship to the other then reapplying gained knowledge to solve).  Confused already?   Solving the “great espresso” equation is actually a problem with seven variables.  They are all variables that interplay with each other.


I’ve interviewed hundreds of applicants and one of the answers I get from experienced baristas is “To get good espresso you pull your shots for 19 seconds.”  Period,  That’s how it’s done.  One magic number.   (I don’t hire those baristas.)


Here are the variables that impact shot taste:  extraction time, volume, grind size, dosage amount, pack pressure, water temperature and water pressure.  And to complicate matters, room temperature and humidity will impact the grind size.  So what’s a barista to do?   We attempt to control as many factors as possible, therefore when we make an adjustment we know what we did and what happened.


Water temperature and water pressure are set on the espresso machine; these can be adjust on commercial machines but generally no one ever changes them.   We train baristas to always pack with the same amount of pressure (30-40 lbs.)  Dosage technique should be the same for all baristas in a shop.  Extraction time and volume are monitored with every shot (we aim for 23-29 seconds and 1.75 oz). So the only variable we regularly adjust is the grind size.


A good scientist or a good barista should approach their work with this attitude: This is what I did and this is what happened. Then make adjustments from there to fine-tune the outcomes.


When training baristas and shot outcomes start to drift, the questions are always: What adjustment are you going to make?  Why are you going to do that?  What do you expect to happen?   Knowledgeable baristas know why their shots drift and know what to do to continue making great espresso.   Bad baristas just keep pulling shots and putting out inferior product.


Randy Stark

Vectors Espresso

Eugene, Oregon


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