"...it should look like regular fog, as seen in long- expired film..."

Kevin:

It should, but something from the packaging or surrounding objects is very likely to be imaged. In my own experience with 120 and 220, it's been the spools and the slots in them.

I've also seen the writing on the backing paper imaged.

However, I've never seen a spec of trouble at an airport carry on machine and thousands of rolls (maybe tens of thousands) of my film have gone through them.

Other xray machines; for checked baggage, at places other than airports with very tight security, and in controled tests, have given me the results I'm describing here.