Exposing printing plates to high-intensity lighting or using light to place images on them.
“Burn” is the term used to refer to dark areas on prints caused by overexposure to light from printing plates; these deposits of ink create dense black deposits on the paper surface that result in dark, dense spots of ink on it. A similar effect occurs with negative and positive film images exposed too long under sunlight.
Printing plates are constructed by applying a layer of light-sensitive material such as photosensitive polymer. When exposed to high-intensity lighting sources, the exposed areas become harder, and the unexposed areas are softened or removed by development processes, leaving behind raised images on the plate.
When an inked printing plate comes in contact with paper, its ink only adheres to the raised surfaces of its plate; those areas where paper comes into contact with it will receive ink transfer from it to create printed images on its surface.
If a printing plate is exposed to too much light during its exposure process, its areas exposed to sunlight may harden too rapidly when inked and brought into contact with the paper.
Burning is an integral component of printing as it determines the final image that appears on paper. By carefully managing this part of the process, printers are able to produce high-quality prints with consistent results – but without adequate control over burning, prints could come out blurry or disfigured, diminishing overall print quality and creating inconsistent results.
Though some printers can get away with less-than-ideal burns, those aiming for top-quality prints know the importance of burn can not be overstated; by taking time and care in creating an ideal burn, they can rest easy knowing their prints meet all industry standards.