lightfast

adj

1. Resistant to fading.

   “Verdigris is lightfast in oil paint, as numerous examples of fifteenth-century paintings show.”

   “Some ink-and-paper combinations are more lightfast than others, and the resulting prints are more fade-resistant.”

   “Tara, a gallotannin, is often quoted as being the most lightfast vegetable tannin and makes very pale coloured leather.”

   “The blue, or cyan, is the most lightfast ink used in the printing process, so it lasts the longest. That blue, incidentally, is the phthalocyanine blue pigment. You can easily test to determine whether any material is lightfast.”