Probably not as well as good quality white paper. Cartridge paper tends to be coarser and less bright paper than good quality copy or printing paper. I can't find any specifics, and there are a number of grades of this type of paper, but the brightness rating appears to be around 76-80%, whereas fair to good quality paper for copying and printing has brightness ratings from 89-94%. These figures represent the reflectivity percent across the visible spectrum.
Beeblebrox.420 Reviewed by Beeblebrox.420 on . paper reflectivity could white cartridge paper work as a reflector? Rating: 5