Barrier paper

A barrier paper comprising a base paper and at least one coating color layer S1 applied directly or indirectly to the base paper, wherein the coating color layer S1 comprises at least one polymer binder and at least one wax, and wherein the coating color layer S1 has at least one of the following features:

• a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m,
• b) change of the polar component of the surface tension of not more than −0.65 mN/m, preferably not more than −0.60 mN/m,
• c) change in the polar component of the surface tension of not more than −3.0% pts, preferably not more than −1.5% pts,
• wherein the respective change is determined by measuring and comparing the measured values of the surface tension and the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105° C. for 3 min.