A Study on doubling in the offset printing process

The purpose of this study was to test the usefulness of the Experimental RIT Doubling Target in identifying directional dot gain in the offset printing process. Doubling, a form of mechanical dot gain, contributes greatly to color variations while printing. Slur, another form of mechanical dot gain, is often confused with doubling. Dot Gain Test Targets currently in use often do not distinguish between the two. A slur test was carried out and the results showed that slur is not a contributor to directional dot gain. The target proved to be a visual and quantitative measure of Directional and Non-directional dot gain. The concentric circles, one of the main components of the target, were made with the intent of matching non-directional dot gain similar to that of a 50% tint made with a 150 line/inch screen-ruling. A slur test was carried out and the results showed that slur is not a major contributor to directional dot gain. The values for dot gain obtained on the concentric circles were found to be higher in value than the values for dot gain obtained on the 50% tint. Nonetheless, there was a strong correlation between the two values of dot gain on both targets. Direction, another aspect of directional dot gain, was studied in relation to the doubling magnitude. It was found that a definite preferred angle for doubling existed. The Pearson Product Method of Analysis, the t test for statistical significance and graphing were used to analyze the data