An apparatus and a method of conforming a blank onto forming surface sections of a forming tool by drawing a first vacuum against an elastic forming medium for transmitting forming forces from the elastic forming medium to the blank. The elastic forming medium is evacuated with the first vacuum for allowing the elastic forming medium to stretch and conform the blank to the forming surface sections. The elastic forming medium includes at least one void. A second vacuum is applied to the void for achieving a stiffened section of the elastic forming medium corresponding with the location of the void and corresponding with, when the elastic forming medium after the completion lies against the forming tool having the blank in between, a forming surface section of the forming tool where the blank requires a forming force being larger than that of surrounding sections of the elastic forming medium.