A process for preparing a mixture of copper phthalocyanine dyes of Formula (1): CuPc(SO.sub.3M).sub.x(SO.sub.2NH.sub.2).sub.y, wherein: CuPc is copper phthalocyanine; M is a cation; x and y each independently have a value of from 0.5 to 3.5; and (x+y)=2 to 5; which process includes: chlorosulphonating a copper phthalocyanine compound using a chlorosulphonating agent; and condensing the product of step (i) with ammonia to give a mixture of copper phthalocyanine dyes of Formula (1); optionally exchanging the cation M in the mixture of copper phthalocyanine dyes of Formula (1) resulting from step (ii) for an alternative cation M; wherein the chlorosulphonating agent includes a mixture of chlorosulphonic acid and a chlorinating agent selected from phosphorous oxychloride and phosphorous trichloride. Also the dyes obtainable from this process; compositions and inks including these dyes; materials printed with these dyes, compositions or inks; ink-jet printer cartridges containing inks made from the dyes; and ink-jet printers including these cartridges.