The PRINTING United Alliance Glossary serves as an excellent industry terminology resource. It is the language by which we all communicate. Without it, universal understanding would be impossible.

To keep our constituents well informed about changes to the increasingly complex industry terminology, PRINTING United Alliance has developed this glossary of terms. 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.
  • Ohms per square
    A means of evaluating the resistance value of an ink mixture, or the resistance value of a square of ink one mil thick.
  • Oil absorption
    The quantity of oil required to completely wet a definite weight of a given pigment, forming a paste.
  • Oil soluble resin
    A resin that will dissolve in a drying oil at slightly elevated temperature to yield an homogenous film.
  • Oil-in-water emulsion
    An emulsion that has water as the external phase and an oil as the internal phase.
  • Oiticica
    A drying oil used in ink formulations made from seeds of licahia rigida tree; similar in properties to tung oil.
  • OJT
    Acceptable acronym for on-the-job.
  • OK sheet
    A press sheet that closely matches the original proof and has been approved by the customer, used as a guide to judge print quality as production run progresses.
  • Olefin
    A chemical family of unsaturated hydrocarbons; also refer to polyolefin.
  • Oleo resinous
    Describes solvents or inks derived from crude oil, or having vehicles compounded from crude oil derivatives.
  • Olephilic
    Oil receptive.
  • Olephobic
    Oil repellent.
  • Oligomer
    (1) A multiple unit molecule consisting of several monomeric units in chemical union; (2) Base resin used in UV ink formulations.
  • On-contact printing
    Screen printing with the print screen in contact with the substrate both during and after printing.
  • On-Demand Color (ODC)
    This term typically refers to short run color printing. These processes include ink-jet, electrostatic and direct-to-press.
  • One-man squeegee
    A squeegee mounted on a counter balanced device so that the operation of very large squeegees can be accomplished with a minimum of effort.
  • One-side finish
    Paper finished on one side only.
  • One-way screen
    A halftone screen having lines running in one direction only.
  • Oozing adhesive
    Adhesive that is forced out from between the face film and backing sheet of pressure sensitive laminates by pressure in die or guillotine cutting.
  • Op art
    Art form using arbitrary patterns of shape, color, and value to create optical illusions or effects that suggest movement.
  • Opacifier
    A chemical agent added to a material to make it opaque.
  • Opacimeter
    A test instrument used to measure the degree of opacity or show through.
  • Opacity
    A state where a printed film or a substrate does not permit the passage of light; the state of being opaque.
  • Opaque (opaquing) (photo opaque)
    (1) An area or material that completely blocks out unwanted light; (2) Red or black liquid used to blockout or cover unwanted clear or gray areas on a negative; (3) White liquid used to cover unwanted black images in an original copy; (4) To paint out areas on a negative that are not to print, refer to blockout; (5) The property of paper that makes it less transparent.
  • Opaque edge (safe edge)
    The edge of a sheet of photoscreen stencil film that has been covered with opaque tape or other opaque instrument, where during exposure develops and washes out with the design portions of the stencil, thus providing a narrow space for handling of the sheet in order to minimize handling damage.
  • Opaque ink
    A screen printing ink that conceals the color beneath it.