Art/Coated Paper or Board Paper or board with a smooth surface created by the application of a coating of china clay compound on one or both sides. Commonly available with a gloss, silk or matt finish.
Backing up Printing on the reverse side of a printed sheet.
Bitmap A grid of pixels or printed dots generated by a computer to represent type and images.
Blanket A rubber sheet stretched around a cylinder to transfer ink from printing plate to paper on a press.
Bleed The area of a printed job that extends beyond the trim edge of a page. Avoids possibility of leaving white edge when guillotining.
CMYK Abbreviation for cyan, magenta, yellow and key (black); these are the four ‘process’ colours used to produce full colour print.
Coating A thin layer of varnish applied after printing to seal the ink and prevent marking. Used predominantly with silk or matt coated papers.
Colour bar A strip of colour swatches printed outside the trim area of the job for the purpose of measuring and maintaining correct ink densities on press.
Colour separation Isolation of each of the component colours of a job, whether process colours or spot colours, for the purpose of producing printing plates.
Crop marks Printed lines outside the area of the finished job indicating where to trim after printing. Similar marks are also used to identify areas for perforating or folding.
Die cutting The process of cutting paper or card to a bespoke shape using a specially-made ‘die’ or ‘cutting forme.’
Digital printing A relatively new range of printing technologies best suited to short-run work or jobs that require some form of variable data. The majority of these printing technologies use toner rather than ink, one of the advantages being that printed sheets do not require drying time. This allows for very quick turnaround of jobs. Set-up times and costs are also much lower than those for litho printing.
Dot gain When printing with wet inks the size of the printed dots can vary due to absorption by the paper – the more absorbent the paper stock, the more the ‘spread’ of the ink. This spread is called dot gain and is compensated for at the repro stage of the workflow.
DPI Short for dots per inch: a measurement of the effective resolution of an image or other types of rasterized artwork.
Dummy A mock-up of the final printed product, using the materials intended for the full production run.
Duotone A non-CMYK image reproduced using two spot colours.
Encapsulation The process of enclosing a printed sheet within plastic laminate film, usually with a sealed perimeter, to protect the job within. See ‘Lamination.’
EPS Encapsulated PostScript, a file format commonly used in the printing industry. EPS files are often ‘vector’ artwork which is not resolution dependent and can be enlarged without loss of quality.
Four colour process Another name for full colour printing, using the four process colours of cyan, magenta, yellow and black.
Full colour As distinct from spot colour or monotone printing, full colour printing uses the four process colours of cyan, magenta, yellow and black to reproduce a wide gamut of colours.
Grain The fibres within a paper or card are aligned in a direction known as the grain of the paper. This has implications, amongst others, for print finishing as folding “against the grain” will often result in cracking along the spine. “Short grain” is the condition where the fibres run parallel to the short edge of the sheet, and “long grain” is the condition where the fibres run parallel to the long edge.
Greyscale Shades of grey, ranging from black to white, reproduced in print by laying down halftones of black ink.
Gutter Gap left in planned-up artwork between two pages.
Halftone Picture with varying shades of tone created by varying size dots.
Hickey Sometimes called a ‘bullseye’ this an imperfection in the print usually caused by a flake of hard ink transferring to the printing plate or blanket.
Imposition The planning up of document pages ready for printing so that they fall in the right place at the finishing stage. The imposition is dependent on the number of pages, format, type of binding etc.
Inter-leaving The positioning of blank, usually thin, paper between printed sheets to prevent wet ink transferring from one sheet to another.
Knockout Describes the condition in colour separation where the colours behind an object are removed. See also Overprinting and Trapping.
Lamination The application of a thin, transparent plastic film to the surface of a printed sheet, to protect and/or enhance the finished job. See ‘Encapsulation.’
Lithographic printing Litho for short, this is the most prevalent printing process and works on the principle that water and oil repel each other. Areas to be printed receive and transfer oil-based ink to the paper, whereas non-printing areas are covered with a thin film of water which repels the ink. See also Waterless Printing.
LPI Short for lines per inch: this refers to the quality or ‘fineness’ of a halftone screen i.e. the relative size of the printed dots. An image printed, for example, at 133 lpi will look fairly course with obvious dots, whereas an image printed at 300 lpi will have the appearance of continuous tone to the naked eye.
Make-ready The various tasks required to set up a printing press prior to commencing production.
Printing plate A sheet of various materials with special coatings on the outer surface which, when exposed, produce an image capable of being reproduced on press. The plate is loaded onto the printing press where it receives ink from the inking rollers.
Micrometer Instrument used for measuring the thickness of paper.
Offset printing Generally synonymous with lithographic printing, this is a method in which the plate transfers an image to an intermediate blanket, reversing the image in the process. The blanket then transfers the image to the paper stock, reversing it once again to it’s correct orientation.
Origination All of the processes associated with the preparation of a job for the printing process.
Outline text To avoid font issues when a job is rasterized, printers will often ask for text to be ‘outlined.’ This is carried out within the design software. The outlined text can no longer be edited, but as it is still described by vector lines it can be printed at any size without loss of quality.
Overprinting The opposite of ‘knockout,’ an element of the artwork is forced to print on top of any background colours. This is often used for black type on a coloured background, to avoid white haloing if there is any misregistration in the printing process.
Pantone colours Special ‘spot’ colours which are mixed to a known formula. These are often used for accurate reproduction of corporate as the colours are standardized and repeatable. Some Pantone colours are outside the gamut of four colour printing and so cannot be reproduced using CMYK inks. For this reason care needs to be taken when choosing Pantone colours for such things as business stationery.
Perfecting Many presses only print on one side of the paper at a time, with it therefore being necessary to send the paper through the press twice. Perfecting presses are capable of printing on both sides of the paper in one pass.
Process colour See Four Colour Process.
Proof Artwork submitted to the customer for checking and signing off, prior to commencing production. May be submitted in electronic (usually PDF) format or as a printed hard copy.
Registration marks Crosses or ‘targets’ printed outside the area of a job, to aid the printer in lining up the constituent separated colours of the job on press. Misregistration can result in text and images looking blurred with obvious coloured fringes.
Resolution The number of dots (or pixels) per inch in a rasterized image or document. Generally speaking, the higher the resolution the greater the quality and level of detail. As a rule of thumb for high quality printing, images should be saved at 300dpi at the size at which they are to be printed.
Reversed-out or white-out Type appearing white on a coloured background.
RGB The red, green and blue colour space used for computer monitors, televisions etc. RGB colours are produced by light sources and for litho printing need to be converted to CMYK.
RIP (raster image processor) Computer software that converts an electronic file containing various artwork formats into a bitmap file suitable for the printing process.
Sealing The application of a thin layer of varnish to the paper surface after printing to protect against marking. Some varnishes can also be used to enhance the appearance of a job. See also Coating.
Self-cover This refers to a booklet that has the same paper material for the cover as for the inner pages.
Solid An area within a job completely covered by ink.
Spot colour Spot colours are specially-mixed inks, usually confined to one or two-colour jobs. They are very often Pantone colours which follow prescribed formulae, allowing them to be reproduced accurately by printers in different geographical locations. Think of a spot colour as being like a tin of coloured emulsion you might choose to paint your walls. At present, digital presses only print using CMYK colours and can therefore only approximate to spot colours. See also Pantone colours.
Spread Two (or more) pages that appear side-by-side in an open document.
TIFF This is a widely used format for image files, tending to be less ‘lossy’ than the JPEG format.
Tint Any printed colour made to appear lighter by using a halftone pattern of dots with white space in-between.
Trapping A slight overlapping between two adjacent colours to prevent the appearance of white gaps due to misregistration or paper stretch. See also Knockout and Overprinting.
Wash-up Between jobs and at the end of the day, printing presses have to be cleaned down to remove ink from plates, blankets and rollers. Paper dust must also be removed.
Waterless printing This is a variant of lithographic printing which uses special silicone plates that don’t require a film of water to repel the ink. Consequently, waterless litho printing can often produce a sharper, finer dot with brighter colours. In addition, there are environmental benefits as these presses don’t require harmful chemical additives that are used in traditional litho printing.