Comparison of Photochemical Reactions by Conductivity Studies.

Conductivity studies were carried out to study the nature of the photochemical reactions of gum-bichromate coatings and an unconventional coating. The data reveal that the conductivity continues to decrease for the gum-bichromate coating after the exposure has been cut off, whereas fob the unconventional coating the curve practically flattens when once the exposure is stopped. A theoretical model for the above behavior is proposed. Platemaking studies conducted reveal that the unconventional coating is equal or better to the gum-bichromate coating as far as humidity and temperature sensitivity is concerned. The new coating is found to be not tacky at high humidities. Studies on tone reproduction reveal that a sharper dot is obtained on plates coated with the unconventional coating.