Abstract: There is disclosed a method of producing diazotype photoprinting material in which a base paper is withdrawn from a supply roll and transported through a precoating station in which a solution containing a silicon filler is applied to one side of the base paper; the paper is then transported from the precoating station past a plurality of heaters to a sensitizing station in which a solution containing a diazotype sensitizing compound is applied to one side of the base paper; the base paper is then transported past a second set of heaters to a transparentizing station in which a solution containing a water emulsion of a water clear synthetic organic resin is applied to the other side of the base paper simultaneously to render the base paper translucent and to decurl the paper; the paper is then transported past a third set of heaters to dry the paper to a moisture content of about 4% and finally is wound into a roll. A method of transparentizing any water absorbent natural fiber material is also disclosed.