Well, this is with my stock Rancilio Silvia 2shot basket. I am getting a lot of fines in the cup. Nothing worse than taking that last sip of a cappa and getting a mouthful of fines. I am hoping this is due to the stock basket, so I ordered a LM 2 shot basket (should be here any day). If the LM still produces these fines is it a grinder problem (Rocky grinder). Thanks

just don't drink the last sip.

Ive only had this happen a handful of times in the almost 2yrs Ive been at this. Im not really sure what the exact cause is, or at least I cant find a consistent cause.

The two times I distinctly remember espresso having a slight gritty finish, was back when I had just gotten my first real machine and was hell bent on pulling super tight ristretto's. Once I learned how to properly pull shots of espresso, its happened maybe once more?

Are you pulling real tight shots maybe?

At double LM large holes.
Presence of small fractions in a cup testifies that diameter of these fractions allows to weep free through basket holes.
When I had an inexpensive grinder I too observed it.

does seem like my rocky grinder produces a fair bit of dust. Guess I can try increasing grind size, dosing a little more and tamping a little harder. I haven't been very impressed with the rocky, might have to bite the bullet and upgrade..

Within possible, of course, it is possible to increase size of fractions. As it is necessary to increase a dose. Double LM it is limited 21-22 grams, if a head of the dispersive screen of the small size.

On this theme the helpful information
Burrs, Carriers, Micrometers & Math OR Why some [KA] grinders s*ck

i don't think that grinding coarser (and dosing up to maintain proper flow rate) will solve your problem, as fines production is not that highly dependend on grind setting (at least not in those boundaries in which you can change your grind setting an still get a decent espresso).

i also don't think that changing the basket will make it any better.

as you rightly suspect, rocky is probably at fault. i never used one, but from what i read built quality seems to be not at its best (or is fluctuating)

what i also noticed is that fines production is (to a certain level) dependent on the coffee used. i especially noticed it with coffee from one roaster who used rather long roast profiles where the beans' final moisture content was lower than with beans of other roasters. these beans were likely to block the glass filter of my cona even at very coarse grind settings.
i know that mainly the grinder is at fault. using an espresso grinder (even a well built one) for vacpot is suboptimal, but with beans from others roaster it kind of worked at much finer setting without blocking the filter...

regards
Georg

Maybe once or twice a year, grit appears in the cup.

It's always coffee related. Changing grind provides little remedy.

If hazarding a cause, beans past their prime / badly roasted

Ok, here is my cup after, big clump of nastiness.



As for beans, these are various beans roasted in my Behmor 1600 and rested for 2days before use. They look and smell great. I basically run them on an espresso profile and hit the cool down at the first sign of 2nd crack. I grind per shot, I put 18gm in the rocky and it tends to grind out just enough for a 25-30sec shot. One thing I found odd about my Rocky from the start is my grind setting is 0, and all the pics online people seem to have theirs at 10-13. I found the zero point was below zero on the grinder scale, like 2-3 below zero. I actually had to take a screw out of the hopper so it would go backwards... then if I set anything higher than zero shots are rapid. I might take the grinder back to the cafe where I got it and have them pull a few shots to see if they get fines, something just doesn't seem right at all. I had a mazzer mini a few years ago and all shots were clean.