Offset printing forme and method of producing it

The offset printing forme according to the invention is a carbon-steel plate on whose surface printing and non-printing elements are arranged. The printing elements are made of the material of a copying layer based on o-naphthoquinone diazidesulphonic or -carboxylic acid derivatives or of the material of a copying layer which is a photopolymerisable composition. The said printing elements form a relief over the surface of the plate. The non-printing elements are made of the hydrophilised metal of the plate, the hydrophilised carbon steel. The method of making an offset printing forme is to apply a copying layer based on o-naphthoquinone diazidesulphonic or -carboxylic acid derivatives or a copying layer which is a photopolymerisable composition to the carbon-steel plate. After the said copying layer has been dried, the image of a transparency is copied onto it, the transparency being a diapositive if a copying layer based on o-naphthoquinone diazidesulphonic or -carboxylic acid derivatives is used, or a negative if a copying layer is used which is a photopolymerisable composition. The image is developed by removing the regions of the copying layer from the non-printing elements using a 0.2 to 1.5% strength aqueous solution of alkali-metal salts or alkali hydroxides at a temperature of 18 to 25 DEG C. The non-printing elements are hydrophilised using an aqueous solution containing 5 to 10% of a salt formed by an alkali metal and an inorganic cyanide complex and 0.5 to 2% of an organic hydrophilic colloid at a temperature of 20 to 25 DEG C. The invention can be used in the graphics industry.