A challenge in formulating dye-based ink-jet inks that exhibit improved lightfastness is a phenomenon known as catalytic fading. This commonly refers to the fact that a given dye may fade faster when it is in contact with another dye as a result of an image area containing more than just one of the inks.However, components in the ink and the media can also act as photocatalysts. For example, hydrogen donors initiate reduction of azo dyes, and singlet oxygen oxidizes them. An explanation is that the absorption of radiation in the UV or visible range can raise one of the dyes or ink components to an excited state. This can then either initiate reactions leading to degradation, or the energy is transferred to another dye whose excited state is at a lower level. In such an excited state, the dye becomes more reactive and is prone to degradation if it cannot quickly dissipate this excess energy away. Hammet constants and molecular modeling were found to be useful tools for correlating fading data.If the source of the excitation is UV radiation, then UV absorbers can be incorporated into the formulation, or the image can be coated with an UV protective laminate that would also guard against any humidity effects. However, when the source is absorption of visible light which is what generates the color, then the problem becomes somewhat more complex. Quenchers can be added which serve as acceptors of the energy from the dye's excited state. Aggregation of the dye can also minimize the effect such that it is more pigment-like.
P. Doll, F. Shi, S. Kelly, W. Wnek, "The Problem of Catalytic Fading with Ink-Jet Inks" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP14), 1998, pp 118 - 121, https://doi.org/10.2352/ISSN.2169-4451.1998.14.1.art00029_1