A process for permanently reshaping keratin fibers comprising mixing a component A and a component B to form a reducing composition. The component A comprises at least one thiol-based reducing compound having one thiol group selected from the group consisting of thioglycolic acid and derivatives thereof, thiolactic acid and derivatives thereof, 3-mercaptopropionic acid and derivatives thereof, and cysteine and derivatives thereof, and has pH 7.0 or less and the component B comprises at least one buffer salt selected from the group consisting of carbonates, bicarbonates and carbamates, and has pH 8.0 or more, wherein at least one of the component A and component B comprises at least one disulfide compound that is further defined, and wherein the reducing composition has a pH ranging from 7.0 to 7.8 and a viscosity ranging from 500 cps to 100,000 cps. The reducing composition is then applied to the keratin fibers.
