Picking

Rupturing or other deformation of a paper's surface caused during ink transfer by the force of a sticky ink either separating the layers of a paper, forming a blister-like protrusion in the paper, or removing portions of the paper's coating. Picking occurs when the force of an ink film exceeds the paper's pick resistance, or surface strength. (See Pick Resistance.) There are two forms of picking: dry picking happens when water is not present; wet picking is the result of decreased pick resistance stemming from exposure to moisture prior to printing. Tearing is an extreme form of picking that rips off the paper surface, leaving a delaminated portion on the press sheet, and splitting is the tearing off of large areas of the paper surface, which then stick to the blanket. Small particles that are picked out of the paper surface are called pickouts. Picking is also called plucking.

Picking also describes a similar problem of gravure printing in which bits of the substrate are transferred to the impression roller or other roller.

The term picking also refers to a printing problem occurring in multi-color flexographic printing in which the plates of successive colors remove bits of the first printed color, commonly caused by printing on still-wet ink. Flexographic picking can be alleviated by ensuring that the first down color has the most rapid drying time.

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