Glossary / S

Sack paper
See "Kraft paper".

Safety paper
Papers with a special protection against abusive imitation. The safeguards used during the production of the paper – some of them chemical – are secret.

Sanitary papers
The group of sanitary papers includes cellulose wadding, tissue and crepe paper, made from waste paper and/or chemical pulp – also with admixtures of mechanical pulp. As a consequence of the importance of tissue today, this name is now used internationally as a collective term for sanitary papers. These grades are used to make toilet paper and numerous other sanitary products such as handkerchiefs, kitchen wipes, towels and cosmetic tissues.

Sanitary tissue paper
Tissue is a sanitary paper made from chemical or waste paper pulp, sometimes with the admixture of mechanical pulp. It has a closed structure and is only slightly creped. It is so thin that it is hardly used in a single layer. Depending on the requirements the number of layers is multiplied. Creping is made at a dryness content of more than 90 %. The dry creping (unlike with sanitary crepe papers) and the low grammage of a single tissue layer result in a high softness of the tissue products. For consumer products it is normally combined in two or more layers. The flexible and highly absorbent product [is mainly produced from chemical pulp and/or DIP – sometimes also with admixture of groundwood pulp] can also be provided with wet strength. Applications: facial tissues, paper handkerchiefs, napkins, kitchen rolls, paper towels, toilet paper.

SC
See Supercalendered.

SC paper
SC stands for supercalendered. This is a calendered, uncoated mechanical paper with fillers.

Secondary fibre
See Recycled fibre.

Security paper
Woodfree, sometimes rag–containing but always high quality paper with a genuine multistage watermark to avoid falsification.

Semi–alkaline pulp (SAP)
Sulphite pulp cooked at slightly alkaline pH (normal sulphite pulp is cooked at acid pH). SAP is superior in strength to normal sulphite pulp. Used mainly in printing papers.

Semi–bleached
Pulp bleached to a brightness somewhere between that of unbleached and fully bleached pulp.

Semi–chemical pulp
High yield pulp in which the fibres have been separated mechanically after a preliminary chemical treatment; e.g. NSSC pulp.

Settleable solids
Suspended solids that will settle out of an effluent during mechanical treatment.

Sheeter
Machine for cutting the paper web into sheets.

Short fibre
Applies to paper or pulp containing a high proportion of short wood fibres.

Sized paper
Sizing reduces the water absorbency of the paper and thus creates the condition for the writability with ink. Sized paper is also used for many other purposes (printing, coating, gluing, etc.), and the sizing agents must fulfil a wide range of tasks. For instance, they control the water absorbency and increase the ability to retain water and ink (pick resistance).

Sizing
Treatment of either stock or paper surface with size to improve strength and reduce absorbency of water.

Sludge handling
Compaction and dewatering of sludge separated from treated effluent.

Softboard
Softboards are soft, bulky boards with a felt–like character. They are used for protective covers, roofing papers, beer mat boards, packaging boards and flongs.

Solid fibre board
Collective term for all solid board grades.

Special pulps
Chemical pulps used for purposes other than ordinary papermaking (e.g. in textile production).

Speciality paper
The group of speciality papers comprises numerous paper grades, each characterised by particular properties. These properties often require special raw materials.

Spent liquor
Waste liquids from pulping and washing (cf. black liquor).

Steam calendering
See steam finishing.

Steam finishing
A way of treating paper before calendering to improve its density and surface smoothness.

Steaming
Wood chips are often treated with steam prior to pulping; used in thermomechanical pulping.

Stock
Suspension in water (slurry) of fibres and other components for papermaking during the period between defibration and web formation.

Strength
Ability of paper or board to withstand mechanical stress.

Suitcase board
Sized, high–density and strong board which generally is water repellent on both sides as a result of surface finishing. It may be pressed, folded, moulded, bent, riveted and sowed. Thickness 1 – 3 mm.

Sulphate pulp
Chemical pulp produced by cooking wood in a liquor containing sodium hydroxide and sodium sulphide.

Sulphite pulp
Chemical pulp produced by cooking wood in a liquor containing sodium, magnesium, ammonium or calcium bisulphite.

Supercalendered (SC)
Paper treated in a supercalender, usually separate from the paper machine; uncoated magazine paper.

Supercalendering
Treatment of paper on an off–machine supercalender to improve smoothness and gloss.

Surface treatment
Treating the surface of paper or board with size or coating colour.

Surface–sized paper
Paper that has been sized on the surface, generally using a size press inside the paper machine.

Suspended solids
Bark, fibre and other wood–based material released into water during debarking and pulping; filler and coating colour residues from paper mills; solid impurities formed during waste water treatment. Solids can be removed from waste water by settling or filtration.

Synthetic fibre paper
Papers made from synthetic fibres such as polyamide and polyester, from viscose staple fibre or sometimes also with fillers. The fibres are mainly held together by binders. The durable synthetic fibre papers are used for maps and highly important documents such as driving licences or vehicle registration books.