Wad
Term for the
resilient backing of the liner in a screw cap closure.
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Warp
Deformation,
normally in the form of twisting, for example of a corrugated board sheet or
a plastic object.
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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.
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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.
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Watermark
A design or image
pressed into the wet paper sheet by a dandy roll during manufacture.
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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.
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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.
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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).
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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.
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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.
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Weathering resistance
The ability of a
package or packaging material to retain its physical properties and
appearance despite prolonged exposure to weather.
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Weatherometer
Laboratory device
for subjecting surfaces to simulated outdoor sunlight and weather conditions.
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Web
The continuous strip
of paper, foil, film or other flexible material which is passed through the
machine during conversion and processing.
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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.
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Welding
Increasingly popular
side seaming method for metal cans. No lead is used; welded seams can be
either lapped or butted.
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Well Cap
A closure for a
container in which there is an interior recessed opening into which an
applicator may be affixed.
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Wet strength
The physical
strength of material when saturated with water. Papers are often specially
treated to improve their wet strength properties.
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Wet strength paper
Treated papers which
can sustain extensive contact with water without losing their strength
properties.
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Wet trapping
Printing wet colours
of ink over other wet colours of ink; common with both multicolour sheetfed
and web production.
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White (glass)
A trade term for
clear, transparent glass as used for bottles and jars.
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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.
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Wicker
Plaited or woven
strands of natural fibre which can be formed into baskets and other
containers.
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Wide-mouth bottle/jar
A glass or plastic
container with a finish or opening which is large relative to the diameter of
the body.
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Window carton
A carton with a
die-cut opening, usually covered by a transparent film, to permit partial
visibility of the contents.
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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.
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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.
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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.
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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.
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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.
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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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