Azo dyes, forming on the material; printing; regenerated celluloses, dyeing.--In producing upon the fibre azo dyestuffs insoluble in water, the material is first treated with a solution of an acid, acid compound or compound yielding acid by hydrolytic or thermal dissociation, there is then applied a mixture of a substantive coupling component with a diazoamino compound soluble in water, in which the group imparting solubility is in the radicle of the stabilizer which does not take part in the formation of the dyestuff, and the dyestuff is then developed by steaming. Specified acids and acid compounds are sulphuric, phosphoric, lactic, tartaric, glycollic and oxalic acids and acid salts, e.g. sodium bisulphate, and specified compounds yielding acid are the sulphates and chlorides of magnesium, zinc and aluminium, ammonium salts of organic acids, esters, e.g. diethyl tartrate, succinate and malonate, ethyl laevulinate and hippurate, dibutyl diglycollate, esters of phosphoric and boric acids, amides, e.g. a -chlorisovalerianamide, malonamide and oxamide, and alkali salts of certain inorganic or organic acids, e.g. potassium fluorosulphonate, sodium 1 - acetoxyethane - 2 - sulphonate, sodium bromacetate and the sodium salt of oxalic acid methyl ester. Specified coupling components are naphthols, arylamides of 2 : 3-oxynaphthoic acid, of 2 : 3-oxyanthracenecarboxylic acid, of oxyphenanthrenecarboxylic acids and of o-oxycarbazole-, o-oxybenzocarbazole- and o-oxynaphthocarbazole-carboxylic acids, pyrazolones, arylamides of acetoacetic, benzoylacetic and terephthaloyl diacetic acids and di(acetoacetyl)-benzidine or -tolidine. The diazoamino compounds may be, for example, those described in Specification 320,324, 329,353, [both in Class 2 (iii)], 427,803, 429,618, 433,878, or 443,222. The following examples are specified: (1) a fabric of unloaded natural silk is impregnated with dilute sulphuric acid, dried, printed with an aqueous composition containing caustic soda, tragacanth thickening, the diazoamino compound from diazotized 5-chloro-2-methyl-1-aminobenzeneand 4-sulpho-2-aminobenzoic acid, and the 2<1>-toluidide of 2 : 3-oxynaphthoic acid, again dried, steamed, rinsed and soaped at the boil to obtain a full yellowish red print; (2) unloaded silk is impregnated with dilute ammonium sulphate solution, dried, printed in adjacent parts with aqueous compositions containing (a) caustic soda, tragacanth thickening, the diazoamino compound from diazotized 5-chloro-2-methoxy-1-aminobenzene and sarcosine, and the 4<1>-chloranilideof 2 : 3-oxycarbazolecarboxylic acid, (b) thiodiglycol, British gum, gum arabic, sodium chlorate, acetic acid, green chromium acetate, the chromium complex compound of the dyestuff from nitrated diazotized 1 : 2 aminonaphthol-4-sulphonic acid and b -naphthol and the chromium complex compound of the dyestuff, 2-chloro-4-toluidine --> 1-(5<1>-sulpho2<1>-salicylsulphonyl) phenyl-3-methyl-5-pyrazoline, again dried, steamed, rinsed and soaped at 40 DEG C. to obtain a brown and black print; (3) unloaded natural silk is impregnated with a dilute solution of diethyl tartrate, dried, printed in adjacent parts with aqueous compositions containing (a) denatured alcohol, caustic soda, tragacanth thickening, the diazoamino compound from diazotized 5-chloro-2-methyl-1-aminobenzene and 4-sulpho-2-amino benzoic acid, and di-(acetoacetyl)-tolidine, (b) potassium carbonate, sodium formaldehydesulphoxylate, tragacanth thickening and the vat dyestuff from 4-methyl-5-chloro-7-methoxyisatin and 5 : 7-dichloro-oxythionaphthene, again dried, steamed, rinsed, oxidized with hydrogen peroxide, again rinsed and soaped to obtain a yellow and blue print; (4) a viscose cr<\>zepe fabric is impregnated with a dilute solution of diethyl tartrate, dried, printed with an aqueous composition containing caustic soda, tragacanth thickening, the diazoamino compound from diazotized 2 : 5-dichloraniline and 5-sulpho-2-methylaminobenzoic acid, and the 2<1>-anisidide of 2 : 3-oxynaphthoic acid, steamed, rinsed and soaped at the boil to obtain a vivid yellowish red print; (5) a viscose fabric is impregnated with a dilute solution of diethyl tartrate, dried, printed in adjacent parts with aqueous compositions containing (a) urea, caustic soda, tragacanth thickening, the diazoamino compound from diazotized 1 - amino - 4 - benzoylamino - 2 : 5-dimethoxybenzene and methyltaurine, and the anilide of 2 : 3-oxynaphthoic acid, (b) thiodiglycol, starch-tragacanth thickening, acetic acid, violet chromium acetate and Galloviridine GA, steamed, chalked, malted, rinsed and soaped to obtain a navy blue and bright green print; (6) a viscose cr<\>zepe is impregnated with a dilute solution of diethyl tartrate, padded with an aqueous composition containing ethyl alcohol, caustic soda, tragacanth thickening, the diazoamino compound from diazotized 5-chloro-2-methoxy-1-aminobenzene and sarcosine, and the 4<1>-chloranilide of 2 : 3-oxycarbazolecarboxylic acid, dried, printed in adjacent parts with aqueous compositions containing potassium carbonate, sodium formaldehydesulphoxylate, tragacanth thickening and (a) the vat dyestuff obtainable by condensing 1-aminoanthraquinone with isophthalic acid (80 per cent) and terephthalic acid (20 per cent), glycerol and anthraflavine, (b) the stable leuco compound of 6 : 6<1>-diethoxythioindigo (cf. Specifications 334,920, [Class 2 (iii)], and 352,283), steamed, rinsed, oxidized with sodium perborate and acetic acid, again rinsed and soaped at the boil to obtain a yellow and orange print on a dark brown ground; (7) a wool muslin fabric is impregnated with a dilute solution of diethyl tartrate, dried, printed with an aqueous composition as in (3) (a) above, steamed, rinsed and soaped at 80 DEG C. to obtain an intense yellow print; (8) a wool-viscose mixed fabric is impregnated with a dilute solution of diethyl tartrate, dried, printed with an aqueous composition containing caustic soda, tragacanth thickening, the diazoamino compound from diazotized 4-chloro-2-methyl-1-aminobenzene and 4-sulpho-2-aminobenzoic acid, and the 2<1>-methyl-4<1>-methoxyanilide of 2 : 3-oxynaphthoic acid, steamed, rinsed and soaped hot to obtain a full bluish red print. 5 - Sulpho - 2 - methylaminobenzoic acid is obtained by condensing 5-sulpho-2-chlorobenzoic acid with methylamine.