Abstract: The invention relates to an agent and uses for treating and improving building materials, mineral mixtures and mineral colours, and to a corresponding method. The aim of the invention is to create an agent, a method and uses of the above-mentioned type which enable old and new capillary-porous building materials, mineral mixtures and mineral colours to be rendered hydrophobic, with both high efficacy and a simple handling process, simultaneously providing the same with a long period of protection, and/or to protect said materials from humidity, without affecting a subsequent coating of the material, the mineral mixture or the mineral colour, without strongly reducing the vapour permeability thereof, and without modifying the inherent colour of the same. To this end, the agent contains between 60.0 and 75.0 mass % of water, between 15.0 and 22.0 mass % of soap, between 1.0 and 7.0 of mass % of a carbonate compound, between 2.0 and 6.0 mass % of sodium hydroxide, and between 1.0 and 7.0 mass % of filler.