Glossary Of Terms

The SGIA 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. SGIA 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 SGIA assumes no responsibility for the use of information presented herein.


  • Rack
    A series of usually flat platforms of open construction stacked or hinged one over the other on which printed sheets may be placed for air drying at ambient temperature.
  • Rack drying
    The air drying of screen printed sheets in racks, usually at ambient temperatures, but can also be dried in a room where temperatures are elevated.
  • Racking
    The placing, manually, of screen printed sheets on racks for drying.
  • Radiant energy
    A form of energy consisting of the electromagnetic spectrum that travels at 299,792 kilometers (186,206 miles) through vacuum, reducing speed in denser media such as air and water.
  • Radiant tube
    A steel tube of alloy or ceramic composition where fuel is burned for supplying radiant heat to a lehr or kiln.
  • Radiation (rad)
    Ultraviolet or infrared wavelengths of light and heat energy used for curing an ink film or exposing a photostencil.
  • Radical
    An extremely reactive chemical particle with an atom or group of atoms with at least one unpaired electron, also referred to as free radical.
  • Radio frequency welding
    A method of joining thermoplastic using radio frequency field to apply the necessary heat.
  • Radiometer
    An instrument, usually self-contained, for measuring UV energy inside of a curing unit.
  • Radius
    (1) A line segment joining the center of a circle with any point on its circumference; (2) A measure of the curve or range on which a printing screen travels in printing tapered objects; (3) Measure of the curve on which artwork is distorted to fit a curved or tapered surface of a bottle or cylindrical object.
  • Radius printing
    The technique of screen printing on conical shapes, where the printing screen moves along the arc of a circle while the squeegee remains stationary.
  • Rag content
    (Also rag paper or cotton fiber content paper) Paper made wholly or partially from cotton fibers that may be derived from reclaiming fabrics or virgin cotton. (Rag papers may contain from about 25% to 100% fibers).
  • Ragged
    A type of composition set where lines of type do not start or end at the same position; lines of type centered in a column.
  • Raglan
    A type of sleeve sewn with seams slanting outward from the neck to underarm.
  • Railroad bond
    A heavy-duty signage board ranging in caliper from 0.457 to 0.610 millimeters (.018 to .024 inches).
  • Rainlap
    The various sheets of an outdoor poster are laid-out and printed so that when posted, the bottom edge of the top sheet will overlap the top edge of the bottom sheets.
  • Ramp (registration lug)
    A registration lug, protrusion, or cavity that is molded into a container or jar; refer to ACL lug.
  • Random access memory (RAM)
    The high speed portion of computer memory that is stored on special chips for use in current applications or procedures.
  • Range
    A measure of dispersion equal to the difference or interval between the smallest and the largest set of quantities.
  • Rapid tensioning
    A method of stretching mesh to optimum tension in one or two steps.
  • Raster
    The process of rendering an image or page, pixel by pixel, in a sweeping horizontal motion, one line after another.
  • Raster image
    An image that is defined as a collection of pixels arranged in a rectangular array.
  • Raster image file format (RIFF)
    A storage format used with gray scale images.
  • Raster image processing (RIP)
    A process using mathematical algorithms to enlarge and print an image.
  • Rasterization
    Changing vector type image information to raster image information.