Offset printing operates on the principle of oil and water repulsion. The image to be printed is transferred (offset) from a plate onto a rubber blanket and then onto the printing surface (usually paper).

The printing plate typically consists of a metal (usually aluminum) sheet with a photosensitive coating. This coating undergoes a process called "exposure" or "burning," where the image to be printed is transferred onto the plate through exposure to light. Areas of the plate exposed to light become hydrophilic (attract water), while non-image areas remain hydrophobic (repel water).

Before printing can begin, the image or text to be printed is prepared digitally using desktop publishing software. The final design is then transferred onto printing plates through a process known as "plate burning" or "plate imaging."

In plate burning, the digital image is transferred onto a photosensitive printing plate using exposure equipment such as laser imagesetters or computer-to-plate (CTP) systems.

Once the plates are prepared, they are mounted onto the printing press. The press consists of several cylinders, including the plate cylinder, blanket cylinder, and impression cylinder.

The plate cylinder is inked with oil-based or UV-curable inks, while the non-image areas of the plate are kept moistened with water or a dampening solution. This ensures that ink adheres only to the image areas on the plate.

As the plate cylinder rotates, the inked image is transferred onto a rubber blanket cylinder. The rubber blanket then transfers the image onto the paper as it passes between the blanket and impression cylinders.

Because the image is first transferred to the rubber blanket before being applied to the paper, this indirect printing method allows for consistent and high-quality image reproduction.

Offset printing is compatible with a wide range of substrates, including various types of paper, cardstock, and specialty materials. It's suitable for printing on both coated and uncoated paper stocks, offering flexibility in design and finishing options.

Offset printing is commonly used for producing high-quality prints such as books, magazines, brochures, catalogs, packaging, and promotional materials. It's favored for its ability to reproduce intricate details, vibrant colors, and consistent results over large print runs.

While offset printing may have higher setup costs compared to digital printing for shorter print runs, its efficiency increases with larger quantities. Once set up, offset presses can maintain high speeds and produce consistent results, making them cost-effective for large-volume printing projects.