Solid composition for aqueous, viscous formulation

A solid composition comprising:

• (a) at least one anionic surfactant,
• (b) at least one amphoteric surfactant or at least one acyl taurate, and
• (c) at least one alkali metal salt of a free fatty acid,
• wherein the wt.-ratio of (a) the at least one anionic surfactant to (b) the at least one amphoteric surfactant or the at least one acyl taurate ranges from 1:3 to 1:0.1, and the wt.-ratio of (a) the at least one anionic surfactant to (c) the at least one alkali metal salt of a free fatty acid ranges from 1:1.5 to 1:0.01, with the proviso that (a) the at least one anionic surfactant and (b) the at least one acyl taurate are different from each other.