Glossary Of Terms

The PRINTING United Alliance Glossary of Terms serves as an excellent industry terminology resource. It is the language by which we all communicate, without it universal understanding would be impossible. Language and our ideas about how it is interpreted change rapidly. PRINTING United Alliance is aware of this and continues its effort to keep our constituents well informed about changes to the increasingly complex industry terminology. The definitions are for general reference only. Usage may vary between companies, individuals, or national and country customs. The information presented is as accurate as the authors and editors can ascertain and PRINTING United Alliance assumes no responsibility for the use of information presented herein.


  • Photocell
    A device that converts the energy in a light ray into electrical energy; also referred to as photoelectric cell.
  • Photochemical oxidant
    Air pollutant formed by the action of sunlight on oxides of nitrogen and hydrocarbons that contribute to the formation of smog.
  • Photochemistry
    The study of chemical actions influenced by the action of light.
  • Photochromatic ink
    Ink that changes color or loses color when exposed to a UV light source and returns to its original color when removed from the presence of UV light.
  • Photoconductive
    A material that carries electricity in the light and serves as an electrical insulator in the dark.
  • Photoconductor
    An insulator that conducts electricity in the light and serves as an electrical insulator in the dark.
  • Photodegradation
    The chemical breakdown of a substance caused by exposure to light.
  • Photoengraving
    A process of reproducing graphic material by photochemical transference of the image onto a sensitized plate and developing in etched relief.
  • Photoflood light
    Electric incandescent filament lamp that provides a high intensity light source on relatively low current consumption.
  • Photographic filter
    Designed to permit passage of specific colors through the lens to the film; manufactured of glass or gelatin in a various colors for use in front of the camera lens to produce pre-determined effects of colors on the film.
  • Photographic sponge
    A very fine textured, soft synthetic foam composition suitable for removing excess water from freshly processed camera film without scratching the emulsion.
  • Photography
    The process or technique of rendering optical images on photosensitive materials.
  • Photogravure
    A printing process where the image is etched into a plate cylinder; also referred to as gravure.
  • Photoinitiator
    A substance that absorbs light and becomes energized into forming free radicals and promotes polymerization of reactive monomers and oligomers.
  • Photomechanical transfer (PMT)
    (1) A diffusion process whereby positive, reversal, or negative print can be made without an intermediate negative process step, also refer to diffusion transfer; (2) A trademark of the Eastman Kodak Company.
  • Photometer
    Instrument used for measuring luminous intensity, luminous flux, illumination or intensity.
  • Photomicrography
    The process of photographing minute objects magnified through a microscope.
  • Photopolymer
    A plastic that changes upon exposure to light.
  • Photopolymer emulsion
    A pre-sensitized emulsion where a photoreactive salt is attached to the polyvinyl resin during manufacturing, requires no additional sensitizer; also known as SBQ-photopolymer emulsion.
  • Photoreactive resin
    A natural or man-made resin or polymer that chemically reacts with itself or with other polymers under the influence of light.
  • Photoresist
    A light sensitive coating that is applied to a metal surface.
  • Photoscreen
    A combination term used to indicate photographic screen printing stencils or the film or direct emulsions from which the stencils are made.
  • Photoscreen stencil
    Any screen printing stencil made by photomechanical processes.
  • Photosensitive resist
    Printable solution that is not affected by etching chemical but which is designed to be affected by exposure to actinic light applied through a mask to a predetermined pattern and later to the chromium tanning process to stabilize the protected portions of the resist film.
  • Photosensitizer
    A chemical agent that is affected or changed by light or other radiant energy; a substance that absorbs light and passes its energy to another substance which then reacts.