First I’d examine the film with a strong magnifier and verify that the scratches are strictly parallel with the axis of the film and on the base side only.
If any scratches are not parallel to the film axis or if any scratches are on the emulsion side, then clearly they cannot be caused by the pressure plate.
If the pp is the cause, then the surface must have:
1. a burr—more likely on a leading or trailing edge
2. rough particles adhering to the pp
A very close inspection with a strong magnifier in good light should reveal the source.
The PP can be cleaned carefully with a soft cloth moistened in naphtha. The naphtha will help dissolve whatever is holding particles to the pp without hurting anything.
If the finish of the enamel of the pp is roughened, it can be polished with auto body rubbing compound or aluminum polish (mild paste of white rouge). Then the pp must be well cleaned to remove all traces of the fine abrasive polish.
One way that long continuous scratches form is in using reloadable cassettes. After many reloadings, the felt light trap can get particles stuck in the felt. The embedded particles scratch the film in loading the cassette, feeding the film forward, and in rewinding the film back into the cassette after shooting.
Last edited by Ian C; 01-22-2012 at 10:41 AM. Click to view previous post history.