In 1875, Robert Barclay invented the offset press for printing on metal. Then, in 1904, Ira Washington Rubel adapted the technology for paper. This indirect method of printing is based on a very simple chemical phenomenon: the repulsion between oil and water.
The printing process is anything but simple though. An offset plate is divided into two areas: the image area, which is lipophilic and therefore attracts the ink; and the non-image area, which is hydrophilic, and repels the ink. The plate is dipped in a solution that binds to the non-image area, and then inked. In this way, the ink only adheres to the image, which is then transferred first to a rubber cylinder and then printed onto the paper.