Differential gloss is the gloss difference between substrate and the imaged areas and between imaged areas of different toner lay-down. This study is to determine the amount of differential gloss on an EP print that's visually unacceptable. Our experience and previous studies indicate that certain amount of gloss is desired on EP prints regardless of paper types. And too much differential gloss might not be acceptable by the end users. Two experiments were conducted using several EP engines with various fusing controls to generate prints with a wide range of gloss and differential gloss. The finding is that differential gloss is not an issue as long as the finished surfaces of an image is perceived uniform.
C Jeffrey Wang, "Differential Gloss in Electrophotography" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP15), 1999, pp 406 - 407, https://doi.org/10.2352/ISSN.2169-4451.1999.15.1.art00009_2