tearing , blistering , delamination and other defects in deep drawn plastic laminated paperboard containers are eliminated by adding controlled amounts of warmed moisture to the paperboard immediately prior to forming thereof . water is heated to a desired temperature and is applied by in - line processing equipment to the unlaminated side of the paperboard which functions to both soften and paperboard and preheat the laminate . by heating both the male and female parts of a die press employed for forming the preheated , softened laminate into the container , preheating the laminate using warm water prior to forming and , continuously controlling the moisture added to the paperboard , the degree of stress imposed on the plastic layer of the laminate and the resulting defects in the formed container are significantly reduced .