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Register In printing, the fitting of two or more images (usually separate colors) on top of each other in -exact -alignment.
Release layer A very thin layer between the photopolymer layer and the Mylar coversheet. This layer remains on the surface and minimizes direct contact with the photopolymer. This layer also allows adjustments of the negative prior to exposure. During processing, this layer is removed.
Relief Depth of the image on the plate; the difference between the total plate thickness and the floor thickness.
Repeat The printing length of a plate cylinder, determined by one revolution of the plate cylinder gear.
Reproportioning See Film Reduction .
Resins Natural or synthetic complex organic substances with no sharp melting point which in solvent solution form the binder portion of the flexographic ink.
Resolution The quantification of printout quality using the number of spots per inch.
Reverse printing Printing on the underside of a transparent film.
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Safe light Light which passes through a filter to screen out rays that are harmful to sensitive material (film, plates, etc.).
Saturation The extreme degree of concentration beyond which a solute can no longer be dissolved into a solvent or, similarly, in which a substance can no longer be absorbed into another medium.
Screen angles The direction that halftone dots run as a result of screen positioning during the conversion of continuous tone art to halftone film. A set of angles often used are: black 45°, magenta 75°, yellow 90°, cyan 105°.
Screen printing In flexo, refers to any tone printing work (halftone).
Screen ruling The number of lines or dots per inch on a halftone screen.
Screen sizes Designated by the number of halftone dots in one linear inch, or centimeter, of perpendicular or horizontal ruling.
Separations A set of three or four continuous tone or halftone photographic films made photographically or electronically from an original subject. Each film represents one of the printer colors abstracted and are used to make printing plates in color process printing.
Shadows The darkest area of a reproduction. Represented in a halftone by the largest dots.
Shelf Life The length of time that a container, or a material in a container, will remain in an acceptable condition under specified conditions of storage.
Shoulder A sloping area adjacent to or long the edge of a higher, more prominent, or more important part such as the halftone or line images on the plate surface.
Sleeve An intermediate used for the mounting of Flexographic printing plates to allow rapid press changeover. In a sleeve based workflow, the finished plates are mounted onto a thin reusable or disposable shell which can then be mounted directly on to integral cylinders or bridge adapters in a cantilevered flexo press.
Solvent The medium used to dissolve a substance.
Solvent plates Flexographic printing plates that are designed to be developed in a solvent washout plate processor. See thermal plates .
Solvent less See Thermal development .
Specific gravity The ratio of the weight of a body to the weight of an equal volume of water at the same specified temperature.
Step and Repeat The act of or equipment for the positioning and exposing of multiple complete images on film in preparation for plate making.
Stickyback (U.S) Double faced adhesive-coated material used for mounting printing plates to the plate cylinder; may be hard tape or cushion tape. Known elsewhere as 'double-sided tape'.
Still bottom Solid or sludge remaining in the solution recovery unit after the reclamation process. The majority of this sludge is unpolymerized plate material from the processing (washout) process and there remains a minimal amount of solution as well.
Substrate A foundation material on the surface of which a substance may be deposited by printing, coating, etc.
Swell A gradual expansion in thickness of the plate from the original thickness due to the absorption of solvents.