Measurements of Ink Transfer in the Printing of Coated Papers.

Using the reproducible laboratory printing techniques described last year, studies were made of the effect of major printing variables on ink transfer and print quality in the letterpress printing of black solids. The effects of printing pressure, printing speed, and ink film thickness were investigated with six oil based inks on four different coated papers. When percent ink transfer was plotted against amount of ink carried on the plate, a characteristic curve resulted. As the ink film thickness on the plate increased, the percent transfer rose very rapidly from the origin, reached a maximum, and decreased again to approach a constant value. With the inks and coated papers used in these studies, the amount of ink required to produce a fully covered print always occurred after the peak of the transfer curve. Both the position of the transfer curve and this minimum practical film thickness were found to be dependent on printing pressure and speed and on the ink and paper properties.