Accelerated Yellowing of Paper after Deposition of Aqueous Cosolvent Solutions.

Water-based inkjet inks typically contain 5-50 wt % of so-called cosolvents, which are nonvolatile, polar compounds such as glycerol or ethylene glycol oligomers (EGOs). We found that the yellowing of printing paper in sunlight is notably accelerated after the deposition of aqueous solutions of EGOs. Using a combination of accelerated aging and fluorescence spectroscopy, we identified the root cause to be the increased rate of UV-induced degradation of whitening agents in the presence of atmospheric oxygen and EGOs. Such fluorescent brighteners are standard additives in office paper.