During the last 10 years it was shown that Deff – MR curve pattern is unique and very useful. This ability was firstly embedded in the procedure for setting up the fast drying regimes several years ago. This incredible pattern was used again in this invited paper. Actually, if the test samples formed from the same clay do not crack during drying in at least two isothermal experiments in which drying air temperature was different, while drying air humidity and velocity were constant, the unique line can be constructed. This line is linking corresponding Deff – MR curves through the same characteristic point. For simplicity reasons it was chosen to construct and use only the unique line pulled through characteristic E points. Its slope was proposed as the objective criteria for evaluation of the clays suitability for the rapid drying application. It was found that clays, for which the unique line slope is larger, had better dimensional and mechanical properties and were more suitable for the construction of the fast drying regimes
