- GHOSTING An image which appears as a lighter area on a subsequent print, due to local blanket depressions from previous image areas. Marring of a print by an image on it of work on the reverse side which has interfered with its drying, so that differences in the trapping of some colours or gloss variations are apparent.
- GLOSS Gloss can refer to the reflectivity of paper itself or of the printed result on it. Gloss of paper is measured by using a gloss meter, which measures reflected light at an angle of 750, and is expressed in Gardner gloss units – the higher the number, the glossier the paper surface.
- GRAIN DIRECTION A term applied to the machine direction of papers or boards, as opposed to the cross direction.
- GRAMMAGE The term used to denote the weight of paper or board; the measurement used is the weight of a single sheet of one square metre, expressed as grammes per square metre (g/mTh
- GREASEPROOF PAPER Paper which resists grease, or prevents the fats found in some goods from soaking into it; the paper is produced by prolonged beating in the pulp stage.
- GREEN PAPER Immature paper which has not been conditioned or had the opportunity to mature naturally.
- GRIPPER A device on a printing machine for holding the sheet during the printing or similar cycle.
- GRIPPER ALLOWANCE The margin of paper along the gripper edge of thesheet held by the grippers and which therefore cannot be printed.
- GRIPPER EDGE The edge of the sheet presented to the gripper. The edge of the plate which is fitted to the leading clamp of the cylinder.
- GROUND WOOD PULP Mechanical pulp made by grinding wood against an abrasive surface, e.g. a stone.
- HALF-TONE The representation of tonal gradation by an image composed of dots of varied sizes, the centres of which are equidistant.
- HALF-TONE SCREEN A grid in which the lines and spaces are of equal thickness and equidistant used in photographing an original for plate or block making.
- HARDWOOD PULP Pulp obtained from the wood of hardwood trees by various processes. The fibres are generally shorter than those of softwood pulp.
- HEAD BOX See FLOW BOX An elevated tank or container equipped with an overflow device which, when supplied with excess of a liquid or fluid, can deliver same at a constant hydraulic head to a lower point.
- HEAT-SET INK A printing ink produced to dry by the application of heat after printing.
- HOT MELT COATING A method of coating with a 100 per cent solids compound of wax, resin of polymer, or mixtures thereof, heated to a fluid state and applied to the substrate by, for example, a roll, gravure or extrusion process with a subsequent chilling device.
- HYDROGEN PEROXIDE BLEACHING A method in which pulp is bleached in an alkaline environment with hydrogen peroxide, sometimes using oxygen reinforcement. The method considerably reduces the need for chlorine-containing chemicals in the final bleaching of chemical pulps.
- IMPRESSION CYLINDER That cylinder of a printing machine which supports one surface of the sheet or web while the other surface receives its printed image from a co-operating blanket cylinder.
- INK RUB A defect, often associated with mart coated papers, in which parts of a dried ink film are removed by pressure or friction from another surface.
- INTEGRATED MILL A mill which starts with logs or wood chips and first produces wood pulp which it then processes to make paper or board; there are only five integrated mills in Britain.
- INTERMITFENT BOARD MACHINE A machine for producing sheets of thick board by winding the web formed on a Fourdrinier wire or cylinder mould(s) around a making roll to form a sheet consisting of several layers. When the thickness is sufficient the layers are cut, so forming a sheet which is removed from the machine for drying and any further processing.
- INTERNAL SIZING The addition of materials to the stock, generally in order to increase the resistance of the finished paper to the penetration and spreading of aqueous liquids, e.g. writing ink. Frequently described as engine sizing.
- IVORY BOARD High-quality board made in white or colours with a bright, clear appearance, particularly used for visiting cards and similar high-class printed work. Original Ivory Board was and still is made in Holland, although the grade is made in many countries.