A Method of Specimen Preparation for Reducing Colorant Flooding Errors in the Determination of Ink Strength using Spectrophotometric Measurement of Bleaches

At the 1999 TAGA Conference a comparison of the many variables that can affect the reliability of the determination of ink strength using a universal bleaching white was presented. The most significant error was the time-dependent flooding of the ink or flush colorant at the surface of the bleach. This flooding was shown to produce changes of up to 8% in relative tinting strength during the time required to prepare a specimen and present it to a spectrocolorimeter, depending on the colorant being measured. Small secondary errors contributing to random fluctuations in tinting strength involved the motion of the wet bleach and possible distortion of the cell cover glass. This report documents a new method of specimen preparation that reduces the time-dependent errors down to the level of the random errors. The mixing process is done with a centrifugal mixer to assure uniformity of the bleach. In addition, a new universal bleaching white was developed that incorporates an ultraviolet