A process for forming an image on a substrate comprising applying a composition comprising: (a) a compound of Formula (1) and salts thereof, wherein: M is Cu or Ni; Pc represents a phthalocyanine nucleus of Formula (2); R.sup.1, R.sup.2 and R.sup.3 independently are H or optionally substituted C.sub.1-4alkyl; R.sup.4 is optionally substituted C.sub.1-4-hydroxyalkyl; x is greater than 0 and less than 1.8; y and z are both greater than 0; and the sum of (x+y+z) is 2.4 to 4.5: and (b) a liquid medium: thereto by means of an ink jet printer. Also compositions, inks, compounds and ink jet printer cartridges.