"cloth on my shutter" as the static source; nah! If it IS static, and assuming it's coming from the camera (as opposed to handling in the darkroom), it almost certainly occurs right where the film starts to separate from the roll. An alternate source might be darkroom handling.(posted 8864 days ago)To confirm static, you could try rapidly unspooling, rewind, unspool, etc, etc in a dry darkroom and see if this produces lots of the marks. If so, the best practice is to slow down camera advance and darkroom unwinding; maybe to about half speed of what you've been doing.