In offset lithographic printing, which principle underpins the printing area?

In offset lithographic printing, which principle underpins the printing area?

• A. Oil and water don't mix; printing area is oleophilic.
• B. Printing uses relief engraving.
• C. Printing uses dry toner for ink.
• D. Printing is done on flexible plates wrapped around cylinders.

Answer: (A)

In offset lithography the essential idea is the separation of oil-based ink from water. The image areas on the plate are oleophilic, meaning they attract ink, while the non-image areas are hydrophilic and stay wet with water so they repel ink. This oil-and-water relationship is what allows only the intended image to be printed, with the ink first transferring to a rubber blanket and then to the paper. The other statements describe different methods or features (relief printing, toner-based printing, or the hardware setup) but they don’t capture the principle that governs where ink adheres.

In offset lithography the essential idea is the separation of oil-based ink from water. The image areas on the plate are oleophilic, meaning they attract ink, while the non-image areas are hydrophilic and stay wet with water so they repel ink. This oil-and-water relationship is what allows only the intended image to be printed, with the ink first transferring to a rubber blanket and then to the paper. The other statements describe different methods or features (relief printing, toner-based printing, or the hardware setup) but they don’t capture the principle that governs where ink adheres.