I saw them years ago, Good show! I have been following Bela since the mid '80's, not just a great banjoist, but my favorite musician.

Thanks for posting the photo Andrew! As Andy said, I am going to stop worrying about it. I did not notice it till the other day and probably always had it. Both you and John said you didn't notice it and there are signs of it in your photos. A lot has to do with how one finishes the cup I guess. A quick tip and the grinds don't have a chance to stick to the cup. A really slow tip and they concentrate in a thin line like my photo. A slightly faster tip and it sticks in the pattern of John's. Wider and higher in the cup, possibly less.

Ken

Ken5 wrote:..I am going to stop worrying about it.

I don't worry about it either. But I wonder about it. The few more experienced people who posted in this thread said, no, it's not typical. But very few had any comment, which is a kind of comment in itself. Questions left unanswered.

Mottling, or flecking, suggests that fines go into the cup, no? Though I have sometimes wondered if mottling is a defect as many machines produce clean crema. Seems that it is highly regarded though. Is it?

Looking at the grounds that are left in my cup I would say that they seem bigger than fines. I might try and shake out some fines to soak them for a minute to see if they achieve that size.

Ken

Sure, suspended solids are a distinctive trait of espresso. If you filter that out you have a different drink. But the bigger pieces seem out of place. So how common is it to see that? And if it's unusual why are we getting some?

Fines are generally considered to less than 100 microns. To get espresso with high clarity you need to filter it down to about 50 microns. The Robot basket holes are about 300 microns, a size shared by other baskets. A 250 micron particle could certainly fit through. Does the Kinu grinder produce a larger number of particles that size?

jpender wrote: A 250 micron particle could certainly fit through. Does the Kinu grinder produce a larger number of particles that size?

Question is, would we see one if it did? These pieces that I have a seem rather big.

With the naked eye humans can see objects about 100 microns (a tenth of a millimeter) in diameter. So 250 microns is easy to spot.

Coffee particles aren't perfectly spherical so you could have two of the dimension less than 300 microns and one dimension much larger than that. It's also possible that the particles may come through early in the shot and then swell in the cup.

Blurry photo of what remained after an Americano this morning (ruler is millimeters):