Erik van Straten
Veteran
The heads of the screws that mount the lip on the take-up reel side could have caused the scratches if they were not in the emulsion layer but on the back of the film, but they are.Hmmm. I suspected it was the lip on the side of the take-up spool. This is where the film is pulled inward as it winds up, emulsion side out.
Otherwise it might be due to the film chafing on itself as it is wound up onto the take-up spool.
Significant scratches also occur along the length of the film between the image and the perforations. These scratches could have been caused by the film rails. I have now smoothed the start and end points of these rails with a tiny file.
Erik.