Andy posted this yesterday on Portafilter.net. I thought it deserved as wide an audience as possible. Basically, measuring your shots by weight is much more consistent, tells you more about what is in the shots and produces the most useful information when baristas compare notes. The post is here: http://portafilter.net/?p=503 .
i just pulled a double - 19g dose, 30 sec, ~55ml total volume. the shots weighed 28g, and once the crema dissipated on one shot (i had them in shotglasses) the volume was about 20ml (so 40ml total after about a minute).
obviously, 55ml of water weights 55g. is the discrepancy due purely to the emulsified state of the espresso and the co2 therein?
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