Espresso Extraction Ratios

January 2nd, 2007

(slightly revised post)

Speaking of Andy Schecter I must say that I am now a fully paid up member of extraction ratios when it comes to defining espresso drinks. I suppose I had always agreed with it but had been unable to put anything to the test because I didn’t have a good enough set of scales. Until now.

It is really great to have a set of lab balances that are accurate to 0.1g up to 1500g. I picked them up second hand so they may be a little old and beaten looking, but they still work very well. This means that I can now not only weigh shots, but also weigh portafilters as I go just prior to insert which means I can see how much I am dosing and how accurate my techniques are.

For those of you unfamiliar with all this the premise is relatively simple. Weight the amount of coffee you use and then weigh the amount of liquid you end up with afterwards. This, to me, seems superior to volume as it isn’t really influenced by the freshness of the coffee. A very fresh coffee tends to brew with a fluffier crema, as does a naked shot, but if we let the foam collapse we might find that 2oz through the naked is actually a different volume of coffee to 2oz from a spouted pf. With these two volumes it is possible to come up with an extraction ratio which is a very easy thing to communicate and use as a standard when comparing shots with someone else. (Divide the weight of the dry coffee by the weight of the liquid and multiply by 100 to make a percentage – I had this back to front first time I posted!).

At Home Barista Andy published this table

This is the new, simplified table:

After a session of weighing today I discovered that most of the espresso I enjoy is around the 60% mark, edging away from espresso slowly into ristretto (going by the table). What was also interesting was to analyse my habits with a naked portafilter versus spouted. Be it habit or a trick of the eye I woud typically pull a slightly shorter shot (in liquid terms) giving it a higher extraction ratio. Am I alone or are we all a little guilty of this? Are we attributing the mouthfeel from the naked when it is mostly down to it being a stronger shot? I don’t know.

I am not saying that this table is law, nor should it be. But I do think that with the right equipment it is easy to compare shots for shots (certainly with those we only meet online) if we are talking about brewing the same thing – regardless of machine or some degree of roast freshness. Perhaps the numbers in the table are a little too rigid or convenient, but that doesn’t dampen the idea for me one bit.

Still – you need a decent set of scales for this. Anything cheap is likely to be pretty inaccurate, certainly around the higher numbers. God bless you ebay…. (If anyone knows where I can get a manual for a random KTron scale then please let me know!)
[tags]espresso, brewing ratios, coffee science, barista, extraction ratio, coffee ratios, ristretto, lungo, home barista, andy schecter[/tags]

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