Do you grind out stale grounds before before dosing your portafilter? You know; run the grinder for a couple seconds to push out any grounds that were retained from last time and then just throw them away.
It’s something I often do and depending on the grinder you're using and how you use it, it may be the only way to be certain you’re getting a completely fresh dose.
So I have seven well know grinders here and I tested each to see how much ground coffee it retains after grinding. I’ll have detailed results of my tests in a minute - there were a couple of surprises, so be sure and stick around for that. I’ll also have some usage tips and opinions, and things I picked up when working with the seven grinders side by side for a day.