A process for permanent shaping hair, especially human hair, comprising the following steps a- optionally washing the hair with a cleansing composition and towel drying, b- applying the ready-to-use composition obtained by mixing the compositions A and B immediately before application onto hair at a weight ratio of A to B in the range of 10:0.1 to 10:1, and leaving it on the hair for 1 to 45 min, c- optionally rinsing-off the hair with water, d- optionally applying an intermediate treatment composition comprising one or more inorganic salts and having a pH from 2 to 7, e- applying a fixing composition comprising one or more oxidizing agents, preferably hydrogen peroxide, and having a pH in the range of 1.5 to 5 and leaving it on the hair for 1 to 15 min, f- optionally rinsing off from hair, g- optionally drying, wherein the composition A is an aqueous composition comprising one or more reducing agents, one or more alkalizing agents and has a pH in the range of 7.5 to 12, and wherein the composition B comprises i) one or more carboxylic acids having three or more carboxyl groups and/or their salts, and ii) one or more additional organic acid and/or their salts having one or two carboxyl groups, wherein the composition B comprises the acids of i) and ii) and/or their salts at a total concentration from 10% to 100% by weight, calculated to the total of the composition B, wherein the ready-to-use composition has an alkaline pH in the range from 7.3 to 11 and comprises the acids and/or their salts at a total concentration in the range of 1% to 10% by weight, calculated to the total of the ready-to-use composition, wherein the hair is put under tension before, during or after application of the ready to use composition, and wherein the tension is released from hair before or during application of the fixing composition or prior to rinsing off the oxidizing agent form hair. a- optionally washing the hair with a cleansing composition and towel drying, b- applying the ready-to-use composition obtained by mixing the compositions A and B immediately before application onto hair at a weight ratio of A to B in the range of 10:0.1 to 10:1, and leaving it on the hair for 1 to 45 min, c- optionally rinsing-off the hair with water, d- optionally applying an intermediate treatment composition comprising one or more inorganic salts and having a pH from 2 to 7, e- applying a fixing composition comprising one or more oxidizing agents, preferably hydrogen peroxide, and having a pH in the range of 1.5 to 5 and leaving it on the hair for 1 to 15 min, f- optionally rinsing off from hair, g- optionally drying, i) one or more carboxylic acids having three or more carboxyl groups and/or their salts, and ii) one or more additional organic acid and/or their salts having one or two carboxyl groups, wherein the ready-to-use composition has an alkaline pH in the range from 7.3 to 11 and comprises the acids and/or their salts at a total concentration in the range of 1% to 10% by weight, calculated to the total of the ready-to-use composition, wherein the hair is put under tension before, during or after application of the ready to use composition, and wherein the tension is released from hair before or during application of the fixing composition or prior to rinsing off the oxidizing agent form hair.