Retorts

More on Lights

With regards to Michael Taylor's letter [Retorts, Dec/Jan], I have noticed a similar phenomenon in the darkroom when removing 120 B&W film from its backing paper. Often there is a marked flare as the adhesive separates from the film, but I have never noticed any corresponding light effects on the developed emulsion.

While at school I remember fellow constructivists making Leyden jars out of plastic Vim bottles coated inside and out with aluminium foil. These were charged by vigorously rubbing an old piece of tractor tyre on the thigh, and the charge transferred to a ball bearing on top of the jar. Unsuspecting students were then invited to hold the jar while touching the ball bearing!

The obvious charge is friction producing static electricity. On holiday in Switzerland at an altitude of about 4000 feet, I noticed that merely rolling over in bed was enough to produce spectacular flashes of "sheet lightning".

J.C. Welch, RNZAF Woodbourne