Test Methods for the Water Sensitivity of Photobooks

Abstract

Water sensitivity is one of the potential degradation routes of digitally printed images. ISO standards 2836 and 18935 are test methods for water fastness. These are shown to have limited application to some water fastness failure routes of printed images in books. As a result they only have limited applicability to the emerging photobook technologies.ISO 18935 contains 3 test methods. These test the resilience of a print to water spill, wet wiping and total immersion. However, these water exposure routes are not always pertinent to images within books which often spend most of their lifetime closed. In this case the water exposure is commonly by percolation through the exposed edge, resulting in chromatography effects on the exposed image, a very different scenario than those covered in ISO 18935. This renders ISO 2836 less useful too.The paper proposes a suitable test object and geometry for testing printed images within books. The strengths and weaknesses of this approach to in-book testing of images are also examined and the reasons for this choice of geometry are covered.The work concentrates on various plain, uncoated papers to best illustrate the effects and examines ink / media interactions using a number of different ink sets. The effect of UV brighteners within the paper is also examined as a part of this work.This work examines the issues around water sensitivity of inkjet prints within books and as such has direct relevance to photobook assemblies. As such it aims to form the basis for an extension to ISO 18935 to these increasingly important media for photographic hard copy.