Skip Ribbon Commands
Skip to main content


Paper & Pulp Dictionary Glossary "W"

Copypaper logo

 Definitions for commonly used terms, words and phrases used in the pulp and paper trade



A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z


Wall Paper
A paper used for wall covering. Also known as hanging paper.
The machine direction yarns in a woven fabric (press felt, dryer screen etc.) See also weft
A process of separating spent cooking or bleaching chemicals from pulp fibers.
Wash Press

One type of pulp washer; uses pressing action for dewatering and displacement.

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-Color Paper
A medium weight, hard sized, coarse surface paper, suitable for painting with water based colors.
Water Finished Paper
A high glazed paper produced by moistening the sheet with water or steam during calendering.
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 fibers' ability to take up water and swell. The WRV is also highly correlated to the bonding ability of kraft fibers.
Water Vapor Transmission
The rate of water vapor 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.
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.
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.
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 leveling 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 fibers 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.
Coating or impregnating of paper or board with paraffin or wax.
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.
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.



Acids and bases

To control pH
Alum Control pH
Improves Retention
Attach additives on fibers
Part of Rosin-alum sizing
Coloring chemical (dyes & pigments) Impart desired color
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.
Fiber Deflocculants Reduce fiber 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 fibers 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
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.
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 sulfide 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). Click to see Picture 1  2
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.
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
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.
Pulp furnish without mechanical pulp.
Wood Pulp
Mechanical or chemical pulp made from wood (cf. Non-wood pulp).
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.
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.
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.
Copypaper logo