paper money with similar counterfeiting resistance. Substrate Polypropylene and other polyolefin pellets are extruded and combined to create a molten polymer, which consists of a 37.5µm thick polypropylene sheet sandwiched between two 0.1µm polyolefin sheets, creating a thin film 37.7 µm thick. This is gravity-fed through a snap-cooling brass mandrel, reheater, blown into a large bubble using air pressure and temperature, and collapsed at the base of the four-storey chamber into a flat sheet by convergence rollers; the sheet is then slit. This creates the base biaxially-oriented polypropylene substrate of 75.4 µm thickness, called ClarityC by Innovia Films. Two 3 µm thick layers of white opacifier are applied to the upper and lower surface of the substrate, except for masked areas that are intended to remain transparent. These overcoat layers protect the substrate from soiling and impart on it its characteristic texture and increase the overall thickness to 87.5 µm. The resulting product is the Guardian substrate. The holographic security foil is then incorporated into the base substrate. This is then cut, and the sheets are spooled onto a roll that is transported to the banknote printing companies in wooden boxes as a secure shipment. Printing Printing banknotes involves several ordered stages. These include acquisition and preparation of necessary materials, prepress activities, printing, and post-printing operations. Some of the operations are "unique to the security printing industry". Prepress activities include creation of the wet and dry plates for lithographic printing, the image and ink transfer plates, and establishing the electroforming and electroplating process for intaglio. The cylinder and roller plates are coated or etched with the unique designs for the banknotes. Inks are prepared using a "mixture of varnishes, pigments and additives". The printing process involves the substrate passing through presses for lithographic printing, intaglio printing, numbering printing, and varnish printing. The inks are transferred using the prepared plates, which are replaced when worn. The opacifier layers enable the inks of the offset and intaglio printing to adhere to the substrate. The varnish printing stage applies a required protective varnish to the polymer substrate. Offset printing deposits a 1.5 µm layer, intaglio about 24 µm, and the protective varnish is about 2 µm thick. Once printing is complete, the banknotes undergo a finishing stage in which they are cut and are then packaged. The packages are stacked on a pallet that is then bound in plastic wrap and strapped. Banknotes