Abstract: A printing machine for use with paper roll stock is disclosed. The print head consists of an expandable cylindrical ring print head where the printing brushes are integrated in a spiral pattern around the ring print head. Ink wells are located outside of the print head, and electromagnets, located outside of the ring print head, attract or repel the print brushes towards or away from the ink wells or paper. The printing machine is ideally suited for advertising or other elongated print media. Due to the use of standard paper roll stock and speed of the printing, signs can be printed on demand and displayed in a real-time basis. Two printing machines can be configured to print on both sides of the paper at the same time with the same or different images being printed on each side.