WADDING Single or multi-ply, loosely matted fibre sheet made from chemical pulp. Used in packaging, thermal and acoustical applications and as a cushioning medium.
WALL PAPER A paper used for wall covering. Also known as hanging paper.
WARP The machine direction yarns in a woven fabric (press felt, dryer screen etc.) See also weft - and The curve of a non-flat board.
WASHING A process of separating spent cooking or bleaching chemicals from pulp fibres.
WASH PRESS One type of pulp washer; uses pressing action for dewatering and displacement.
WASHI Japanese handmade paper. For more detail, please visit
WASHING DEINKING Deinking in which solid particles are separated on the basis of their size by washing. Also see Flotation Deinking and Combination Deinking.
WATER-COLOUR PAPER A medium weight, hard sized, coarse surface paper, suitable for painting with water based colours.
WASTE PAPER All kind of used paper or paper discarded or not considered fit for a particular use.
WATERMARK Designs impressed into paper while in course of manufacture by means of a projecting wire, on the mould, or in the case of machine made qualities on the dandy roll. Watermarks were employed as early as 1282. They served to identify the product of each paper mill and the designs chosen (many of them extremely complicated) also expressed emblematically the tenets of the manufacturers, which were handed down traditionally from father to son. It was customary, and the custom has survived until the present day, for paper mills to use similar designs in common. These standard designs were triflingly modified by each individual maker; they have in many cases been the origin of modem terminology, such as Foolscap, Pott, Post and so forth.
WATER FINISHED PAPER A high glazed paper produced by moistening the sheet with water or steam during calendaring.
WATER RESISTANT PAPER Paper which has been impregnated, coated or laminated to resist the penetration of water.
WATER RETENTION VALUE (WRV) The water retention value test provides an indication of fibres' ability to take up water and swell. The WRV is also highly correlated to the bonding ability of Kraft fibres.
WATER VAPOUR TRANSMISSION The rate of water vapour transmission through containerboard indicates the ability of the finished container to protect its contents from undesirable effects of high humidly or moisture loss of the product.
WATERLEAF A paper with little or no sizing, like blotter, making it very absorbent If dampening is desired, this paper can be sprayed with an atomizer.
WATERMARK The image impressed into the formation of paper by the dandy roll on the wet end of the paper machine; can be seen by holding the watermarked sheet up to the light. Can be either a wire mark or a shaded image.
WAVINESS A form of paper curl resulting when the sheet edges in the pile absorb moisture that the center of the pile cannot absorb; or the sheet edges surrendering moisture while the center remains moist.
WAVY EDGES Warping effect in paper that is the result of the edges of the sheet having picked up moisture and expanded. Will normally happen only in a pile that prevents the center of the sheets from picking up the same amount of moisture and levelling out or cockling. It is usually a warm weather problem caused by improper balance between moisture content of the paper or too high humidity in the air.
WAX PICK A process that measures the ability of inks to pick fibres or particles from the surface of paper as a manner of testing the surface strength of paper stocks.
WAXED PAPER Nearly woodfree papers that are impregnated with paraffin, wax or wax/paraffin/plastic mixtures. With the appropriate saturation agent and process the product may be tailored for specific applications, e.g. packaging of bread or sweets or wrapping razor blades.
WAXING Coating or impregnating of paper or board with paraffin or wax.
WEB Term used for the full width of the paper sheet in the process of being formed, pressed, dried, finished and/or converted.
WEB BREAK A tear in a web during the printing process.
WEFT The cross machine direction yarns in a woven fabric (press felt, dryer screen etc.). See also warp
WET BREAK A paper break at the wet end (on wire or press) during papermaking process.
WET END First part of the paper machine consisting of wire part and press part.
WET END CHEMICAL ADDITIVES Chemical additives added with the stock at the wet end. Following are some of the wet end additives.
WET STRENGTH The strength of a paper product when saturated with water, as determined by tensile testing.
Application
Acids and bases To control pH
Alum Control pH Improves Retention; Attach additives on fibres; Part of Rosin-alum sizing
Colouring chemical (dyes & pigments) Impart desired colour
Defoamers Kill/control foam to improve drainage & retention
Drainage Aids Improve drainage (water removal) at wire/press.
Dry Strength Additives (Starches, Gum) Improves burst, tensile, pick resistance etc.
Fibre Deflocculants Reduce fibre flocculation and thus improve formation
Filler (clay, CaCO3, TiO2 etc.) Improve opacity, printing, surface smoothness etc.
Optical Brighteners Improve optical brightness
Pitch Control Prevent deposition & accumulation of pitch
Retention Aids Improves retention of fibres and fillers
Sizing Chemical ( rosin, ASA etc.) To control liquid (water, ink etc.) penetration
Slimicides Control slime growth and other organisms
Specialty Chemicals Corrosion Inhibitors; Flame Proofing; Anti-tarnish
Wet Strength Resin To impart wet strength to such papers as coffee filter
WET LAP MACHINE Paper machine consisting essentially of a wire covered cylinder rotating in a vat of pulp stock on which a mat of varying thickness is formed by drainage. These mats are removed either intermittently in thick sheets called laps, or continuously.
WET STRENGTH PAPER A chemically treated paper strong enough to withstand tear, rupture or falling apart when saturated with water. Papers to which this term applies retain an appreciable percentage of their mechanical strength after soaking in water, and are made by the addition of a resin to the stock during paper manufacture. This resin cements the fibres together and the bond tends to improve with age. The advantages of printing maps on, or making certain wrappings from, wet strength paper are obvious.
WET TENSILE STRENGTH The measure of the force necessary to break a one inch strip if paper after it has been immersed in water.
WETTING AGENT Substance that increases the wettability of a surface for a liquid.
WHITE LIQUOR White liquor is the aqueous solution of sodium hydroxide & sodium sulphide used as the cooking liquor in Kraft pulping.
WHITE TOP LINER A two-ply sheet comprised of one bleached and one unbleached layer.
WHITE WATER The filtrate from the wet end of the paper machine.
WHITE WATER SYSTEM Flow circuit for paper machine white water (includes pipes, storage tanks, cleaning equipment, water from forming section and return feed).
WHITENESS Whiteness of pulp and paper is generally indicated by its brightness, which is the reflectance of a wavelength of blue light. So-called white papers have a definite hue. Most are made with a blue white tint.
WHOLE TREE CHIP Wood chips produced by chipping whole trees, usually in the forest. Thus the chips contain both bark and wood. They are frequently produced from the low-quality trees or from tops, limbs, and other logging residues.
WICKING The bleeding of ink from the ink jet printing process into unwanted areas of the paper, causing a blurring effect of the printed character or image.
WINDER, REWINDER Machine for cutting the paper web longitudinally into narrower webs, which are then wound to reels; also slitter-winder
WINDING Operation whereby a web of paper or board is wound into one or more reels.
WIRE OR MACHINE WIRE The moving "screen" at the wet end of a paper machine where the sheet is formed.
WIRE GUIDE ROLL The small diameter roll used for guiding (keeping on track) the wire. One end of the roll is adjusted to compensate any misalignment.
WIRE RETURN ROLL (S) The small diameter rolls used at the return run (Couch roll to Breast roll) of the wire.
WIRE MARK On the bottom or wire side of the paper, these are impressed traces of the machine wire.
WIRE SIDE The side of a sheet next to the wire in manufacturing; opposite from the felt or top side; usually not as smooth as the felt or topside.
WIRE TENSION ROLL The small diameter rolls used at the return run (Couch roll to Breast roll) of the wire to adjust the tension of the wire.
WOOD-FREE Pulp furnish without mechanical pulp.
WOOD FREE PAPER or FINE PAPER Paper made without mechanical wood pulp and containing no fibres other than those derived from chemical wood pulping processes i.e. contains no lignin.
WOOD PULP Mechanical or chemical pulp made from wood (cf. Non-wood pulp). TMP and CTMP
WOVE The Paper having a uniform surface and no discernible marks. Soft, smooth finish, most widely used writing, printing, book and envelope paper. Relatively low opacity, brightness and bulk.
WRAP AROUND BLANK A scored and slotted sheet that is machine assembled around a product to make a finished box.
WRAPPER The materials, consisting usually of paper or paperboard, sometimes with treatment for moisture barrier properties, which are used to protect the roll or pile form damage.
WRINKLE Blade Wrinkle: Blade coating defect, an irregular line on the coated surface, essentially in the machine direction.
Winder Wrinkle: Ridges at an angle to the machine direction, caused by hard sport in the reel.
WRITING PAPER Uncoated paper that is suitable for writing with ink on both sides. The writing must neither bleed nor strike through. Writing paper is always fully sized and also suitable for printing. It can be woodfree or mechanical, depending on the intended purpose. The admixture of fillers makes it less translucent.
CONTACT – Email: mark@saxonmachinery.com – Phone: +44 7500 115 23
