The Determination of Humidity Limits to Prevent Colorant Bleed in Inkjet Prints

Abstract

The purpose of the project was to determine the absolute ceiling limits for temperature, humidity, and time combinations to prevent noticeable colorant bleed in photographs and documents printed with inkjet digital technologies. The research focused on a variety of dye printers and papers because it was known from previous work that these printer/paper combinations produced prints sensitive to humidity. The results of this work are intended to help cultural heritage institutions that collect these materials develop policies for use and care to prevent damage to their collections. The results may also benefit commercial services that offer prints made with these processes, as well as artists and photographers and the general public.In this so called “humidity limits” study a series of nine different dye printer/paper sets were included along with one pigment printer/paper combination to serve as a control. Specimens were treated to twelve different time, temperature, and humidity regimes covering a span of time from one day to four weeks, temperatures from 15°C to 35°C and relative humidities (RH) from 60% to 90%. The tests included measuring Delta E with a spectrophotometer for a checkerboard target and line width changes with image analysis software for a CMYK line target. Analysis of the data from the humidity limits study indicated that the behavior of the inkjet dye printer/paper combinations to the various treatment conditions were quite variable.Because institutions collections could contain prints similar to a very sensitive print in this study, a very conservative approach should be taken for their care. However, the results of this study indicate that that inkjet dye prints, even the most sensitive ones, are relatively safe from significant humidity bleed if kept at 65% RH or less.