Glossary

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.
  • 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.
  • Opaque vinyl
    A vinyl that is pigmented, so no light passes through it.
  • Open circuit
    The lack of electrical contact in any part of the measuring circuit, usually indicated by rapid large jumps in potential, followed by an off-scale reading.
  • Open cutter and creaser
    A platen press used for die cutting and creasing.
  • Open end envelope
    An envelope that opens on the short dimension.
  • Open end yarn
    Yarn produced without being spun; a hard, uniformly blended yarn considered inferior to ring-spun yarn.
  • Open gold
    A non-drying gold.
  • Open kiln
    A kiln that exposes the ware directly to the flame.
  • Open side envelope
    An envelope that opens on the long dimension.
  • Operating force
    The force required to achieve contact resistance; the amount of force required to complete a switch closure in a membrane switch.
  • Operational characteristic curve
    A graph that displays the probability of accepting a sample lot as a function of the quality of the lot in process.
  • Optical axis
    An imaginary line that runs through the focus and center of the lens of a camera.
  • Optical brightener
    A chemical used to make white garments whiter.
  • Optical center
    The center of a rectangle as it appears to the human eye, usually a point slightly above the geometric center or about 2/5 from the top of the rectangle.
  • Optical comparator
    A visual inspection device that uses large ground glass screens for imaging; offers a much larger view than a microscope.
  • Optical dot gain
    The change in appearance of the halftone dot to the human eye at normal viewing distances and under typical lighting conditions, or with a densitometer.
  • Optical mark reader (OMR) (optical bar reader) (optical bar recognition) (OBR)
    Electronic equipment that scans, interprets, and converts bar coded information into a machine readable form.
  • Optical registration
    A register system employing an optical scanner for obtaining the correct positioning of substrate on a press.
  • Optical resolution
    The maximum physical resolution of a device. Optical resolution provides better quality than interpolated resolution of the same number, which uses software to create additional image information.
  • Optical reverse
    The use of mirrors to reverse a camera image.
  • Optical sampling rate
    The number of samples in pixels per inch that are taken by a scanner per linear distance, as determined by the CCD array, the optical system, and the motion of the carriage.