A continuous method for the manufacture of a 2-aryl-3,3-bis(hydroxyaryl)phthalimidine comprising continuously heating an anhydride with a phenol in the presence of a catalyst and a first co-catalyst, to form a first reaction mixture comprising a phenolphthalein compound; precipitating the phenolphthalein compound; combining a primary arylamine with an acid catalyst and a second co-catalyst to form a second reaction mixture; adding the phenolphthalein compound to the second reaction mixture; continuously heating the second reaction mixture to provide a third reaction mixture comprising a crude phthalimidine; and treating the crude phthalimidine to remove aminophenol and purify the phthalimidine is provided.