A binary image comprising a plurality of first areas, at which a porous or particulate image-forming substance is adhered to a substrate, and a plurality of second areas, at which the substrate is free from the image-forming substance, is protected by laminating thereto a laminating sheet comprising a durable layer and a support layer with the durable layer facing the image, so that the durable layer adheres to both the first and second areas of the image. The support layer is then displaced away from the image such that the durable layer remains attached to the image. The durable layer is substantially transparent and comprises a polymeric organic material having incorporated therein a siloxane, the siloxane being incorporated into the polymeric material in such a manner that it is not removed therefrom by hexane, isopropanol or water.