When changing beans, finding the right grind setting is sometimes a long process, but it seems I'm getting better at judging grind coarseness by eye. I just made an interesting observation though: I think I can now predict if the grind is too coarse at the tamping stage. Perhaps a bit late in the process; but I've never read anything on that topic here.

It seems to me that the ease with which I can twist the tamper for a quick polish after tamping is correlated with the probability of getting geysers out of my naked portafilter. Once I grind fine enough, the tamper (US-curve convex) usually twist very easily and smoothly. On too coarse grinds, friction is perceptible even if by eye the grinds look fine enough.

by your standards my shots this week would have been terrible. However, I am using a VST sized tamper in the EPNW baskets so it's a tight fit. However, I can tell if the shot will gush by looking at the tamped puck usually.

Yeah well... YMMV apparently It probably depends on the tamper too -- not sure if a flat tamper would spin as well as a convex one and I guess an Euro-curve convex tamper would spin better.

How polished is the bottom of your tamper? I imagine that could make a big difference in how it behaves. I find that moisture adds a huge friction when I'm polishing. On a highly polished tamper I would hypothesize that a finer grind would be stickier. Interesting observation though.

My tamper is not mirror finish but pretty smooth (machined aluminum I guess). Can't comment on moisture though. Moisture could make the grinds stick to the tamper more, or could also add cohesion to the puck and give a smoother surface for the tamper to slide on.

But this morning there was *indeed* a drop of moisture on my tamper and I felt lots of friction: a bit of coffee stuck to the tamper and there was a hole in the puck surface. Otherwise the grind was ok and I didn't know how to elegantly fix this so I just pulled a shot anyway. It was a good shot despite the surface damage on the puck.

I stopped polishing a long time ago; I don't see the need for it. I just lift the tamper carefully (and vertically) from the surface of the puck. My tamper is a Reg Barber C-Flat.

Matt

I just do it for fun But it turned out it can predict geysers up to a point in my case.

polishing for me is just the easy way to get the tamper out of the basket. I've haven't seen improvements removing the step.

Are you sure the "friction" you feel when polishing isn't related to grinds getting stuck between the tamper and basket edge?? I have found that you need to insert the tamper lightly at first then remove the tamper and then tamp with pressure.

If you're using a high quality tamper and basket the tolerances should be very close and any grinds between the edges will result in that friction

I don't think the tolerances are that tight between my tamper and basket walls; my tamper is always easy to insert and as far as I can tell, friction comes from the underside, not the edges.

Anyways, since this is something I notice *after* the grind (of course), it's not really something I can solely use to dial in the grind. When the puck is tamped, I might as well pull a shot and see how it goes.