A printing defect similar to dot gain characterized by printing ink between halftone dots, or in small, non-image areas in type or line art. Fill-in is commonly caused by the presence of debris such as lint, paper fibers, coating particles, or other random detritus trapped in the ink. Ink that has not been well-ground and contains larger and a greater number of pigment particles than usual, that possesses low viscosity and high tack, or even various press conditions can contribute to fill-in. Fill-in is also called specking. (See also Doubling and Slurring.)