A coated substrate such as an adhesive tape is produced by applying to a substrate a solution of a mixture of a rubber (eg. natural rubber) and a tackifier (eg. a petroleum resin) dissolved in a solvent (eg heptane) wherein the solution, prior to its application to the substrate, has been subjected to evaporation in a thin film evaporator so that the concentration of rubber and tackifier in the solvent is at least 35, usually at least 45 weight percent so enabling faster coating speeds.