A Method for the Measurement and Specification of Coldset Process Ink Transparency

Laboratory proofs of the NAA-COLOR(tm) AD-LITHO(r) standard inks were made on black, uncoated paper at a range of ink film thicknesses normally used in coldset lithographic printing. Colorimetric measurements of the unprinted black paper as well as the same area after printing were made with a spectrophotometer and the overall color difference (Delta E*) calculated using the unprinted black paper as a reference. A graph of Delta E* versus ink film thickness was made and the inverse slope of the linear regression line taken as a measure of the transparency of the ink. While based on the method described in our TAGA '94 paper, the black paper was used because a standard opacity chart on newsprint is not available and printed black bars on newsprint were found to give inconsistent results. The practical application of this method was confirmed in conjunction with NAPIM and during the work of ISO/TC130/WG4/TF1 on the proposed ISO 2846-2 standard.