Lithography works on a simple principle that ink and water don't mix. The term “Offset” refers to the process of transferring the image to an intermediate medium before it is transferred to paper. Therefore, offset lithography places the image onto plates which are dampened first by water, then ink. The ink adheres to the image area and the water to the non-image area. A reverse image is then transferred to a smooth rubber mat called a “blanket” (this is the offset part). A reverse image is again transferred from the blanket to paper.

Below is the process for setting up and running a six color Offset Lithographic press:

• Pre-Makeready
• Makeready
  • Check the plates for accuracy.
  • Set the sheet handling mechanism.
  • Pack and mount the plates.
  • Prepare the dampening system.
  • Prepare the inking system.
  • Load the make ready books.
  • Make and examine the trial impressions.
• Press Run
• Wash-Up