- RAG PAPER Paper made from stock containing a substantial percentage of rag pulp. The minimum proportion of such pulp required for a paper to be so designated cannot be specified as it varies from country to country.
- REAM A unit of measurement for sheets of paper; normally 500.
- REEL lIP The final process in t~aking paper; after passing through the drying cylinders and, if appropriate, the calender rollers, the newly-made paper is wound onto a jumbo reel: this is the reel up stage.
- REFINER A machine, usually equipped with discs or with a cone and plug, intended for the treatment of fibrous materials in an aqueous medium to give them some of the properties needed for the manufacture of pulp or paper with the necessary characteristics.
- REGISTER MARKS A set of fine line crosses or other suitable devices added to the original artwork to provide reference points for the subsequent registration of the colours of a set of printed images.
- REINFORCED PAPER Any paper that has been strengthened mechanically by the incorporation of other materials such as plastics, threads, cloth or strips of metal.
- RELATIVE HUMIDITY Quotient of the amount of moisture in air and the amount that would saturate it at the same temperature and pressure, expressed as a percentage.
- RETREE PAPER Paper which has become available as a result of overmaking or side-runs or because it is in some way less than perfect; perhaps non-standard or slightly sub-standard. Although sold without a guarantee the substance and size tolerances would be expected to conform to industry standards. Often referred to as clearance paper.
- RICE PAPER Sometimes a material which has the same appearance and purposes as paper is called paper’. Rice paper is an example, since it is not paper, but the sliced and flattened pith of a plant which grows in Taiwan; it is used by Chinese artists as a surface for painting.
- ROLL COATING Any method of coatings web of paper in which the coating is applied directly to the paper by transfer from an applicator roll which carries the coating slip upon its surface. The applicator roll may rotate in the same direction as the paper web or in the reverse direction (reverse roll coating). SCUM Traces of printing ink which temporarily adhere, during litho printing, to the non-image area of the plate due to its inability to repel ink.
- SECURITY PAPER Paper which includes identification features such as metallic strips and watermarks to assist in detecting fraud and to prevent counterfeiting.
- SELF-ADHESIVE PAPER Used essentially for labelling purposes, this grade has a self-adhesive coating on one side and a surface suitable for printing on the other. The adhesive is protected by a laminate which enables the sheet to be fed through printers or printing machines, the laminate subsequently being stripped when the label is applied.
- SEMI-CHEMICAL PULP Pulp obtained by partial removal from the raw material of those non-cellulosic components that can be removed by a direct chemical treatment, e.g. cooking: to resolve the fibres, some subsequent mechanical treatment is necessary.
- SET-OFF The unwanted transfer of printing ink from a print to a facing surface.
- SHIVES Coarse fragments of fibrous materials present in pulp or paper, resulting from incomplete resolution during pulping.
- SHORT GRAIN The fibres in a web of paper naturally take up an alignment roughly parallel to the direction of travel of the web on the paper making machine; this becomes the grain direction. When cut, the paper’s grain direction may be parallel either to the long edge of the finished sheet (when it is called long grain) or the short edge (short grain). Papers are normally stocked in long grain form, short grain being supplied to special order. The grain direction affects the stiffness in a particular dimension and must be taken into account when planning a job which needs to be folded, as paper usually folds easier with the grain.
- SHOW THROUGH The degree to which a printed film is visible through paper due to the low opacity of the paper.
- SIDELAY A datum point on a printing machine for positioning correctly the side of the sheet in relation to the printed image.
- SIDE-RUN A narrow reel removed from a web during processing, the width of which is less than the size ordered, but is large enough to permit its use for purposes other than re-pulping. An additional part of an order placed in order to better utilise the maximum trimmed machine width of the making machine.
- SIZING This process can either be applied on the surface of the sheet or in the sheet: in the first case starch is applied to the surface to increase its strength and to resist the penetration of oil-based inks (this process is carried out at the size press, which is about two-thirds of the way down the dry end); in the second case chemicals are added to the stock at the pulping stage before the sheet is formed: this is called internal or engine sizing and its purpose is to stop penetration of water-based inks into the sheet.
- SLITTING Dividing a web of paper in the lengthwise direction into two or more narrower webs.
- SMOOTHNESS The surface smoothness of paper is measured by the Bendtsen smoothness test. The test measures the amount of air escaping between an annular ring and the material surface, and results are measured in mllmin. Papers having a value higher than 50 are usually referred to as Matt, below 50 as Silk (sometimes called Satin or Velvet).
- SOFT CALENDERING A relatively new method of smoothing paper. Soft calenders are more compact than other calenders and adopt a system whereby the web is passed between steel and hard rubber rolls. The method permits a wide variety of finishes between gloss and mart and the retention of bulk.
- SOFTWOOD PULP Pulp obtained from the wood of coniferous trees by various processes.
- SOLID BOARD A board comprising a single furnish layer.
- SOLID FIBREBOARD A board, which may be pasted or unpasted, and often incorporating a lining of Kraft or other strong furnish, intended and suitable for the manufacture of fibreboard packing cases and drums.
- SOLVENT-COATED PAPER Paper coated by any suitable coating process with resins or plastics dissolved in volatile solvents which are subsequently evaporated.
- SPLICE Joint in a web of paper in or approximately in the cross direction, made either by an adhesive or an adhesive strip, (a) to obtain a reel of the desired length or
- to permit, for example in a converting machine, a continuous operation between the end of one reel and the beginning of the next.
- SPREAD COATING A method of coatings web of paper by means of a vertical plate restraining a pond of viscous coating material, for example resins, plastics or adhesives, which is drawn through an adjustable gap between the plate and the paper by the forward movement of the web over a horizontal support.
- STACK A type of calender, generally situated at the end of the making machine, of which the rolls are of metal only.
- STOCK The wet pulp before it is fed onto a paper making machine, or during the paper making processes before it becomes a sheet of paper; contains around 99% water and 1% fibre.
- STOCK PREPARATION Collective term for all treatment necessary for the preparation of the stock before it reaches the making machine.
- STRAW PULP Paper making pulp obtained from cereal straws by various processes appearance is made to imitate the fine smooth finish of a
- STRIKE THROUGH The effect seen on the verso of the sheet due to excess penetration of printing ink or vehicle into or through the paper.
- SUBSTANCE The weight of paper or board, shown by scales,taken from a sample. The weight is nowadays almost entirely defined by granimage per square metre of a single sheet (g/m2).
- SULPHATE PULP Pulp obtained by cooking the raw material with a mixture consisting of caustic soda, sodium sulphide and possible other compounds, such as black liquor.
- SULPHITE PULP Pulp obtained by cooking the raw material with a bisulphite liquor.
- SUPERCALENDERED FINISH (SC) A surface finish on paper which may vary from relatively dull but smooth to highly glazed, produced by passing dampened paper through a supercalender percentage of water is eliminated by drainage, suction and press stack. This is broadly similar to a machine calender stack except rollers, leaving a web of paper which then passes to the dryiiig that it is separate from the paper making machine and some of the cylinders rolls are of compressed fibi~e.
- SWORD HYGROSCOPE Portable testing instrument designed the printed colour is still wet, in one pass through the printing for insertion into a stack of paper to assess whether the moisture machine content of the paper is in equilibrium with that of the surrounding.
- SYNTHETIC PAPER Paper produced by conventional means.