Follow Us: Twitter LinkedIn Facebook


Specialty Graphic Imaging Association
SGIA Glossary

Definition Glossary

Sixth Edition

Language and our ideas about how it is interpreted change rapidly. The Specialty Graphic Imaging Association (SGIA) is aware of this and continues its effort to keep our constituents well informed about changes to the increasingly complex industry terminology. This publication represents the most recent changes.

| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | Y


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.


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.


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.


An instrument, usually self-contained, for measuring UV energy inside of a curing unit.


(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).


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.


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).


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.


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.


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 processing (RIP)

A process using mathematical algorithms to enlarge and print an image.


Changing vector type image information to raster image information.

rasterized type

Type that has rough or stair-stepped edges.


A sound made by paper that is shaken for an indication of stiffness or dryness.

raw materials

The components necessary to the manufacture of a product (Basic items or materials in a chemical composition; basic items or materials used in constructing a mechanical device).

raw umber

An inorganic pigment with excellent fade resistance, excellent fade resistance, good resistance to acids and alkali, resists bleeding, poor gloss.


A synthetic textile fiber made from regenerated cellulose (wood pulp), cotton linters, or other vegetable matter.


To redo a portion of or all of a job due to error or defect.

reactive dilutent

Monomer or mixture of monomers used to reduce the viscosity of a UV ink.

reactive dye

Dye that works by forming a chemical bond between the fiber and the solution where heat is used to develop the proper shade, used to make fabric colorfast.

reactive material

A chemical substance or mixture that will actively polymerize, decompose, condense, or become self-reactive under conditions of shock, pressure, or temperature.


The ability of a substance to change by combining with another substance or breaking down.


UV curable unit consisting of UV lamps, reflectors, cooling system, and shielding.