Interaction of Substrates and Rotogravure Etching Processes on Tone Reproduction.

An experiment was designed and a rotogravure cylinder was made which contained gray scales, solid areas, type matter, and reverse type matter from a common original supplied to three companies. From this original, three different screen rulings were used to etch with the Conventional gravure process, four screen rulings with the Dual Positive process, two screen rulings and deep and shallow etching with the Direct Engraving process plus two etching depths of an Experimental Direct Engraving process which used a RespiR contact screen. All of the above variables were on one cylinder which was proofed with five different substrates normally used in the packaging industry. A production press run was made using one of the substrates The tone reproduction curves for each of the variables: (1) process differences. (2) etching depth differences. (3) screen ruling differences. and (4) substrate differences were plotted The Conventional process more nearly approached the Ideal tone curve with most substrates. while the Direct engraving processes showed maximum deviation from the Ideal curve. with one exception Each of the substrates produced a different tone curve, which, in practice should dictate that the photographic and etching requirements for rotogravure should be customized for the substrate and should not be a standard photographic-etching process where only density ranges of the film positives are the controlling standard of the industry.