Crud showing up in C41 negs

[Bosaiya]

I'm not the most experienced C41 developer in the world and could use some help troubleshooting a problem I'm having. I've looked around, and even asked a few people I know, but no luck. I tried contacting support at Jobo but that didn't help.

Some of my negatives are looking like they have blobby crud on them. But only when scanned. When I hold them to the light they look great, but once the scanner filters out the base color I get this crud all over some of them. Most are pristine, but every once in a while... crap.

This is very, very different from dust. I can tell what's dust and what's not, given the size, shape, and dispersion.

I've tried scrubbing the negs with PEC, they still look as clean to my eyes as when they first came out of the tube, but still scan the same. Like I said, there will be one nasty one right in middle of two pristine negs, so it can't be a batch failure.

Any idea what's causing this and how to avoid it?

[my intention is to print these in the darkroom, but that has to wait a little, and I'm worried that this problem will show up in the prints. So I'm checking them on a scanner first to see what I can expect.]

 

[domaz]

Have you totally ruled out a scanner CCD issue (dust, noise etc..)? Is the "crap" in exactly the same position no matter where you mount the negative on the scanner? A different scanner would great to try in this case, or failing that a microscope or good loupe just to confirm it's the film and not the scanner.

 

[Bosaiya]

Whoops, I knew I forgot to mention something!

I've tried moving the negatives around without luck. I even tried flipping them over, just in case.

Looking at the negatives with an 8x loupe shows nothing. But since the crud is the same color as the orange base, I figure it might be hard to tell.

 

[Bosaiya]

This has got to be something on the scanner, probably under the glass. I also think it's got to be related to static or something as well, because it moves around.

The prints seem fine when enlarged traditionally so I'm not going to lose too much sleep over it.