Security features for paper

A method of making a continuous roll of banknote paper on a paper making machine, said banknote paper having a low porosity and having a plurality of discrete transparentised regions repeating along the length of the paper, and also having a plurality of discrete areas repeating along the length of the paper which are at least partly of a lower grammage than surrounding areas, so as to provide lighter and darker areas in said areas which are enhanced by said transparentised regions, said method comprising the steps of

• (a) continuously depositing an aqueous fibrous suspension onto a support surface to form continuous wet paper sheet;
• (b) forming in the wet paper sheet a series of discrete areas repeating along the length of the sheet which are at least partly of a lower grammage than surrounding areas;
• (c) draining liquid from said wet paper sheet to form a continuous unfinished porous absorbent sheet;
• (d) printing a plurality of locations in said unfinished porous sheet with a transparentising resin to provide transparentised regions which cooperate with the discrete lower grammage areas to enhance the visibility thereof, which transparentising resin is absorbed into the sheet;
• (e) passing said unfinished porous sheet having the discrete printed transparentised regions through a surface sizing impregnating device so as to impregnate said porous sheet with surface sizing, such that the surface sizing surrounds the transparentised regions;
• (f) drying the resulting sized porous sheet to form a dried porous sheet;
• (g) calendering said dried porous sheet;
• and
• (h) reeling the resulting sheet into a roll of finished banknote paper.