[avandonk]

If you peel sticky tape off light proof paper covering your plate in the dark and you then find dark areas when the plate is developed that do not look like ordinary static induced dark dendritic faults. You must come to the conclusion that whatever did it went through the light proof paper.

All that is needed to produce xrays is high energy electrons exciting the K shells of any atom they hit. When this K shell electron then drops back to its normal level it emits an xray of characteristic wavelength depending on the type of atom. Triboelectric static discharges in a vacuum allows the electrons to get to far higher energies before they interact with an atom than in air. Lightning bolts emit a surprising amount of xrays although if the xrays intensity scares you don't worry, if you are that close the bolt has already fried you!

I used to do a lot of dark room work in the late sixties at Kodak Research Labs. When you have been well dark adapted say four hours peeling tape of anything emits a lot of light. Even crushing peppermints shows the same phenomenon. Static discharges were a real issue with medical xray film as they could be mistaken for a tumour etc.

Bert