I have the impression that a flat tamper base more often yields an extraction that starts at the outer circle and a convex tamper makes it easier to get an even flow from the complete bottom of the basket right away. So I got a beautiful tamper from www.dirossi.nl and compared the result with the flat base tamper Tije made for me a while ago. In this clip I compare two extractions of the same grind & dose (and music), the first tamped with the convex tamper, the second with the flat one.
