In thermal transfer printing production of offset printing, before the ink was not dry, after a sheet that is stacked on it, the ink on the front of a sheet is likely to move to the back of the rear portion of a sheet, known as the back rub dirty.

The back rub dirty and offset are expressed as the back sheets are dirty marks,but they form a completely different mechanism.

The back rub dirty easily occur after printing coated paper,sublimation ink, overprint color number for a long time, no dirty marks intermediate paper; offset likely to occur in a non-coated paper printed the first color printing and ink printed directly on the back on white paper, while the middle instead of multi-color ink overprint at the back, the paper has a dirty mark, not erased.

Indian goods produced on the back rub dirty has two important stages:First, the ink fixation on the back rub dirty stage, referring to the printing process the paper just reached the collection of paper heap, 3-5 sheets stacked on a sticky dirty; the second is a back rub dirty ink curing stage, referring to the ink has been fixed yet for the before curing, still remain in the softening phase, resulting in the back of the sticky dirty.