The Condition of the Grinds
If you wish to go further and start factoring the TDS of the interstitial liquid of a brew into your extraction calculations, then you have arrived at “the boundaries of coffee!” The world of advanced barista training hasn’t worked this out yet. This is a great example of what makes it so exciting to be a barista and to be a part of the first generation of specialty coffee.
A shift in thinking on this issue has recently occurred, explored in an influential blog post by Scott Rao. Scott identified that no one has yet instituted a reliable system for comparing the condition of coffee grinds at the precise moment a barista considers a brew to be finished brewing.