Voltage ’roll-over

A further electrical method, the use of which is restricted to film (and which indeed is little used at present) is the electro-contact treatment process proposed by Rothacker13 and described by Smith.8 In this, the film is passed over a metal roll and contacted by a number of free-rolling electrodes. A direct current potential difference is applied between the roll and the electrodes, and an a.c. voltage superimposed over the d.c. The flow of electrons thus induced brings... 

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