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Packaging - Glossary - W

  • Packaging Processes

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    The Glossary of the International Trade Centre (ITC) on the technical terms used in the packaging sector is a database designed to provide updated information on the specific terminology used in the packaging industry. This Glossary is a tool placed at the disposal of users for information only. It is not designed to replace the appropriate professional advice in any way. Users are invited to submit their comments and observations by email to Mr. Frederic Couty, Senior Adviser, Export Packaging at the following email address: fcouty[at]intracen.org

    Select an alphabetic above to access the glossary.

  • W

    Wad

    Term for the resilient backing of the liner in a screw cap closure.

    Warp

    Deformation, normally in the form of twisting, for example of a corrugated board sheet or a plastic object.

    Waste

    (1) The loss of materials occurring in the process of manufacture. (2) Material trimmed and salvaged in a processing operation. (3) Material that has become obsolete by use.

    Waste stream

    All products and packaging materials that have to be disposed of or recovered after fulfilling their primary functions. Waste flows may come from various origins, industrial waste such as trims in manufacture, or post consumer waste, i.e. waste of packaging materials at the end of the lifetime.

    Watermark

    A design or image pressed into the wet paper sheet by a dandy roll during manufacture.

    Water-tight

    That quality of a container or pack­age by which it prevents the passage of liquid water either into or out of the package.

    Water Vapour Permeability

    The property of a material that permits water vapor to pass through its structure. This property has measurable values that can be determined under specified conditions of time, temperature and the water vapor pressure differential between two sides of a material or between the inside and the outside of a container.

    Water vapour transmission rate (WVTR)

    Formerly known (incorrectly) as moisture vapour transmission rate. A measure of the permeability of a material to the passage of moisture in the gaseous state (water vapour), not as a liquid. Expressed in g/m2/24 hours at 38 ºC and 90% relative humidity (RH).

    Wax

    An organic compound with a low melting point, now normally of petrochemical origin. Varieties are distinguished by their melting point. Used as a sealant and to provide various properties to paper and board surfaces e.g. heat sealing and impermeability.

    Waxed paper

    Paper or paperboard treated with wax to give it water, vapour or grease resistance.Can be heat sealed to other wax-coated materials.

    Weathering resistance

    The ability of a package or packaging material to retain its physical properties and appearance despite prolonged exposure to weather.

    Weatherometer

    Laboratory device for subjecting surfaces to simulated outdoor sunlight and weather conditions.

    Web

    The continuous strip of paper, foil, film or other flexible material which is passed through the machine during conversion and processing.

    Web printing

    The production of printed goods such as flexible packaging from rolls of paper that are passed through the press as one continuous web.

    Welding

    Increasingly popular side seaming method for metal cans. No lead is used; welded seams can be either lapped or butted.

    Well Cap

    A closure for a container in which there is an interior recessed opening into which an applicator may be affixed.

    Wet strength

    The physical strength of material when saturated with water. Papers are often specially treated to improve their wet strength properties.

    Wet strength paper

    Treated papers which can sustain extensive contact with water without losing their strength properties.

    Wet trapping

    Printing wet colours of ink over other wet colours of ink; common with both multicolour sheetfed and web production.

    White (glass)

    A trade term for clear, transparent glass as used for bottles and jars.

    White Room

    A filling, compounding or and/or packing room where extreme measures have to be taken to assure product and pack sterility/cleanliness.Also called a clean room.

    Wicker

    Plaited or woven strands of natural fibre which can be formed into baskets and other containers.

    Wide-mouth bottle/jar

    A glass or plastic container with a finish or opening which is large relative to the diameter of the body.

    Window carton

    A carton with a die-cut opening, usually covered by a transparent film, to permit partial visibility of the contents.

    Wire-bound containers

    A shipping container made from thin slats of wood held together by metal wire. The lid is hinged by the wire and the closure is made by locking the wire loops together.Also known as a Bruce box.

    Wire tie

    (1) A pliable wire, pre-cut with looped ends, used for closing heavy duty paper bags. The bag is twisted into a neck around which the wire tie is placed and twisted by hand or by special tool. (2) A light wire inserted into a folded, narrow strip of paper, cut into short lengths or used from reels, for tying tops of polyethylene bags to render the opening relatively moisture tight.

    Wood density

    High wood density implies high strength and good resistance to the extraction of nails. Wood densities below 350 kg/m3 are not advisable in packaging applications.

    Wood wool

    Cushioning material made from shredded wood, similar to ex­celsior pads but of much finer texture. This gives a relatively soft and non-abrasive character to the material.

    Woven plastics

    Plastics (polypropylene or polyethylene) films cut into narrow tapes and woven into a fabric widely used for the production of plastic sacks with sewn ends for powder and granular products.

    Wrapper / wrap

    1.  A sheet of flexible material used to cover or enfold a product for storage, shipment or sale. A covering for a tray, carton or other package to retain and seal in the contents and to increase its protective properties or performance.

    2.  A machine for wrapping.

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