I don't recall what cleaning I did right after decap. I also didn't take a picture before the first acetone shake.

Shook about a minute in acetone in a 50 mL PP vial.

Then tried ultrasound and it removed a few larger objectects

Presumably those were lose and the small parts still there are the locations there were attached

This may indicate that the sample needs further acid treatment to be really clean

Then tried doing a standard lens clean with acetone + lens tissue

dropped it onto the metal stage below, but it landed right side up and so I don't think this contributed to any contamination

About the same, one particle appeared and one dissapeared or so

did not help, same particles are there

Looks like there is still a lot of contamination but its not in the same place

Used new fixture to hold sample

Much cleaner

Expect that remaining particulate is mostly lose

Looks exactly the same after

Conclusion: stuff is still stuck on

I then realized that these weren't actually dirt. Close ups:

Ultrasound was more effective at removing large particulates than high pressure acetone.

Ultrasound does not effectively remove undissolved epoxy but it can be removed by wiping

Tearing lens tissue for smaller allotments is a bad idea as it generated particulates. The sheet should be used whole and moved around if it is to be used multiple times.