In a method for the calculation of a temperature T of a solid body of a liquid cooling medium, or the time t needed for a temperature change of the solid body or the liquid cooling medium, the differential equation dTdt=b\u2212cT is converted into a dimensionless differential equation. A multi-ply tissue paper produced by the method is also described. The aqueous high-concentration solution of N,N-dialkylglycine which contains the N,N-dialkylglycine at a concentration of 30\u201380% by mass, and a metal-mineral acid salt at a content of 0.