A Note on Espresso Extraction Ratios

Thanks to some birthday money, I purchased a gram scale for preparing espresso.  In a café situation, it is not feasible to use precision measurement devices all the time, but they are useful for training the eye and the hand to become consistent.  Consistency is the key word in a shop: quickly producing good coffee, more times than not, with minimal waste of product.  At home, I have the liberty of tweaking and perfecting my technique at my own rate, measuring with my devices along the way.  I guess that part of me comes from being a principled diagnostician and a computer tech.  (My wife just says I tweak-happy!)

With that said, Johnny Chappell of Crimson & Whipped Cream in Norman first told me about the idea of extraction ratios.  Jim Hoffman—espresso scientist, critic, and blogger—discussed extraction ratios on his blog in 2007.  Predating this blog post is the lengthy thread over at Coffeed about what espresso is, which includes a sporadic discussion about extraction ratios intermingled with lots of other elitist coffee talk.  Precipitating a lot of this is a character named Andy Schechter over at Home Barista who made a table of idealized extraction ratios.  The table uses quantifiable figures to create a community-accepted definition for espresso in all its incarnations.

Table of extraction ratios, courtesy of Andy Schechter

I agree with the point that extraction by volume can appear deceiving—whether due to freshly-roasted coffee or naked portafilter—because volume is judged by visual measurement (i.e. 1.25oz of espresso with fluffy crema and 1.75oz of espresso with scant crema can appear to measure the same in the glass).  To sidestep this conundrum, extraction ratio has been proposed as the standard.  As a diagnostician, I am in favor of consistent, measurable, reproducible results.  After my discussion with Johnny, I rushed back to work where I hopped over to Jim's blog and began digesting the information  presented there.  Unfortunately, I was without a gram scale like Jim's, so I was unable to achieve his level of consistency—my espresso was hit-or-miss, with miss being more common than hit! 

Simplified extraction ratio

s

The addition of a gram scale and several conversations with other baristas later, I'm sold on this idea.  I was able to pull great espresso almost immediately using extraction ratio as a solid indicator as to the "doneness" of my shot; I coupled extraction weight/ratio with traditional visual cues to ensure that my dosing and packing technique was also within tolerances.  For example, 17g of Elemental Coffee's Espresso 228 extracted to 13g of espresso in 30 seconds, producing a brew ratio of 130.8%, which according to Andy's chart is on the high end of the 'ristretto' range—right where I prefer it!  This particular shot was the closest to café quality I have gotten at home to date.

I am not attempting to preach the gospel according to Andy Schechter or Jim Hoffman, but I am presenting a topic for further discussion because of its perceived merits.  If the community does adopt the ratio method widely, Andy's work may become the model in café's worldwide.  Just remember that a method is only as good as its limitations, and we have not addressed those limitations at length here.  Caveats in a high-volume shop are numerous, and we will discuss those later if it strikes my fancy.  For now, it is enough to say that this method does have merit for use as a diagnostic tool.