A method of sensitizing metal plates with a bichromated, natural water-soluble protein. The exposed image is covered with ink before development, then the inked image is developed with water.

• 以含铬的天然水溶蛋白质使金属版具感光性，印纹的部份在显影之前先以油墨覆盖，然后以水来显影出印纹。