ABSTRACT
An observation from 1887 noted that solid benzenediazonium nitrate turns rose-red on exposure to sunlight.
This sensitivity to light of diazonium salts was exploited in the textile industry as early as 1890 when a process for printing on silk or cotton was devised involving the photo-decomposition, under stencils, of an applied diazonium salt followed by coupling of the residual material with a phenol.
