Glossary of Terms

Pantone, PMS

The full name is Pantone Matching System, or PMS. It's commercial system for describing colours consistently, using reference patches in printed swatch books. These are usually encountered in printing as Pantone numbers specified for a certain colour, often on a company logo or similar house colours. Pantone is very wide ranging, with colour sets for plastics, paints, textiles as well as printable colours.

Paper

The original printing medium, still very widely used for books, newspapers, magazines, brochures, posters, fine art and many other applications. Any printing process will be able to print on paper, although different paper coatings may be needed for specific ink types.

PDF

Stands for Portable Document Formant. It's the dominant file format used for exchanging printable documents in the printing industry. It was developed by Adobe Systems in 1994 as was originally proprietary, though widely used. It is now an ISO standard, developed by a committee, which may explain why it has not changed much in recent years.

PDF/VT

A variant of PDF/X that can include variable data, which is particularly useful for digital printers where every copy can be different. PDF/VT-1 can contain lists of variable information internally, while PDF/VT-2 (so far not released) will be able to reference external databases, allowing the same file to print different content. As with other PDF variants, this is now an ISO standard (ISO 16612-2), with development by committee.

PDF/X

This is a subset of PDF that outputs documents in a tightly defined way, so there is less chance of failure due to unprintable elements if the file is opened and printed by a third party. This is called "blind transfer," because the receiving end doesn't need to have any knowledge of the creation settings, just that it is a PDF/X file (which self-identifies itself).

Phase change ink

A type of ink that is a wax-like solid at room temperature. It is heated in the printhead to become a liquid that is then fired at the medium. It is most commonly used by Xerox in its Phaser range of office printers, but the same company uses a variation of the process in its CiPress series of high end web-fed inkjet production printers.

Picolitre

One millionth of a litre. The usual measure for ink drop sizes generated by inkjet printheads. These typically range from 3to 100+ picolitres depending on the head and nozzle. The smallest sizes are usually confined to greyscale heads for high quality tonal work. See Greyscale Heads, Printhead.

Piezo printhead

One of the types of printhead that generate drop-on-demand printing. A piezo-electric material (which is a type of crystal) has the property of expanding or contracting when an electric current is passed though it. The effect is used within piezo inkjets to form an actuator, which is essentially a pump for the ink within the printhead chamber.

Pigment

A colorant within an ink. Pigments are insoluble, relatively large particles, generally making them more resistant to fading than smaller dye colorants that are fully dissolved.

Pinning

A curing method used with UV cured inkjets. A low intensity burst of UV light starts the curing and stops droplets spreading, but leaves the ink liquid enough to smooth over and give a glossy surface before it is fully cured by a second, higher intensity UV burst.

Pixel

Short for Pixel Element. This is the smallest element of a bitmapped image, visible on a computer screen if you enlarge the image, to show a mosaic of squares. The number of pixels in an image such as a photograph are often mistakenly called its resolution, but strictly speaking the resolution is a combination of the number of pixels and the enlargement factor, to give pixels per inch (PPI).

PNG

Stands for Portable Network Graphics. It's a bitmap file format that was originally developed for website graphics, as full-colour alternative to GIF (which is limited to 256 colours). It supports 24-bit RGB colours but not the CMYK print set. It can hold alpha channels, so objects can display on a website as cutouts. The compression is lossless.

Pop

An informal term for the appearance of an image that has bright, "punchy" colours, or other eye-catching characteristics. An older and entirely different usage to POP as an acronym for Point of Presence. See POS/POP.

POS/POP

Related terms standing for Point of Sale and Point of Purchase. In the printing sector it's often used as a generic description for small printed signs, special offer product boxes and other attention-grabbing items (such as wobblers), positioned on or near the checkout area or counters of a shop or similar retail environment.

PostScript

A device-independent page description language which was behind the desktop publishing revolution of the 1980s and 90s. A PostScript file generated by any program can be printed on any PostScript-compatible printer. Developed Adobe Systems in 1983, PostScript saw its first application in the Apple LaserWriter of 1985.

PPML

Stands for Personalised Print Mark-up Language. It's an XML-based printer language for variable data content. It has been developed by PODI, a multi-developer organisation.

Print Driver

Control software that supplies images to a printer for printing. The driver is specifically written to control a particular printer. It may be combined into a RIP.

Printhead

Also spelt as two words: print head. The core of an inkjet printer: a component containing an array of nozzles that project drops of ink towards the printing medium. See array, piezo printhead, thermal printhead.

Purging

See Flushing.