The purpose of the project was to determine the minimum levels of force and abrasion cycles necessary to produce a just noticeable difference (JND) in objects printed with modern digital presses (documents, book pages, etc.). 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 or manufacturers of the equipment or media. A variety of digital press technologies and papers were studied. Specimens were abraded using the Sutherland 2000 Rub Tester with both ¼-lb and 2-lb loads. The lighter weight was an attempt to replicate physical handling of materials such as page turning in books or sorting sheets in stacks of documents. The use of the heavier weight was an attempt to emulate unbound prints being pulled from larger stacks as well as unbound prints in stacks during transport. The abrading surfaces included unprinted and printed sheets to replicate single-sided prints in stacks or doublesided prints in stacks or books. A series of abrasion cycles were produced for each of the materials to determine when JND could be observed. Visual observations were correlated to average grey values to determine if a quantifiable threshold limit for this property was possible. Additionally, the relative sensitivity of the various materials to abrasion was compared. The tests included measuring colorant smear from a black printed area to an adjacent white area, loss of colorant from the black area, and transfer of colorant to an adjacent sheet. The change in average gray levels were measured with image analysis software for both the black patches and adjacent unprinted areas before and after abrasion as well as the transfer of colorant from printed faces to adjacent unprinted papers. Also gloss measurements before and after were used to determine the extent of gloss change in the black patches. The results show that the major factors influencing the extent of damage from abrasion are the printing technology and the printed paper. From previous work it was known that smear of colorant is more objectionable than gloss change. However, with some digital press/paper combinations noticeable gloss change can be seen before noticeable smear of colorant. While not as severe as smear, change in gloss, especially when it is uneven, is still of concern to museum, library, and archive personnel and patrons. Results from the use of the lighter abrasion weight to simulate the turning of pages or sorting of sheets in stacks This paper was presented at the 4th International Symposium on Technologies for Digital indicated that this should not be a problem no matter which printing technology or paper is used as no noticeable damage was observed either by measurement or visual assessment even after many hundreds of abrasion cycles. The heavier weight showed differentiation of the sensitivity of the different printer technology/paper combinations indicating a greater concern is needed for objects that may be inadvertently subjected to higher forces, especially with digital press inkjet technology.
Eugene Salesin, Daniel Burge, "The Determination of the Minimum Force to Initiate Abrasion Damage of Digital Press Prints" in Proc. Int'l Symp.on Technologies for Digital Photo Fulfillment, 2013, pp 31 - 35, https://doi.org/10.2352/ISSN.2169-4672.2013.4.1.art00010