Offset printing is a printing process in which the inked image is transferred (ie, "offseted") from the plate to an intermediate blanket before being printed on the substrate. Following are the common terms you come across in offset printing.

• Opacity - This refers to the quality of being impenetrable by liquids or light. With paper, it refers to the ability to keep print from showing through to the other side.
• Opaque - In production it refers to a solution or paint used to block out areas on a film negative to keep them from being reproduced on the plate.
• Overprinting - It generally refers to printing an image over another impression. It also refers to printing a secondary color over a primary color in graphic arts work.