Did you ever came across this kind of sediment inside La Pavoni boiler?
It looks like a glued sand on the boiler wall. Maybe coffee residue? I tried to descale with 50/50 vinegar with no results.
The grouphead tube also had this, so I soak it over night in Cafiza. It was still baked on the tube, but I manage to break some of it.
I also manage to break some inside the boiler with a screw driver, but I stopped.

Any idea how to proceed?

hi,
I haven't seen it in person but to me it looks comparable to the 'not descaled in ages' image here:
http://www.francescoceccarelli.eu/lapav ... ri_eng.htm
though less excessive.
a soft copper wire brush may help in getting the sediment loose or more open to facilitate further descaling.
cheers,
Rob

Thanks Rob. I will try the soft copper brush on it.

How long did you let the vinegar sit? Sometimes it takes several days to dissolve a tough scale.

I let it sit for few hours, because I was afraid from over descale. And that was before removing the HE and discover this thick well of residue.

I guess in this case, time is the key.