Woodfree uncoated paper (WFU), uncoated woodfree paper (UWF) or uncoated fine papers are manufactured using wood that has been processed into a
chemical pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemical or plant-based additives, pulp is the major raw ma ...
that removes the
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
from the wood fibers and may also contain 5–25%
fillers
In processed animal foods, a filler is an ingredient added to provide dietary fiber, bulk or some other non-nutritive purpose.
Products like corncobs, feathers, soy, cottonseed hulls, peanut hulls, citrus pulp, screening, weeds, straw, and cere ...
.
The paper made without using mechanical pulp
/ref> Both softwood
file:Pinus sylvestris wood ray section 1 beentree.jpg, Scots Pine, a typical and well-known softwood
Softwood is wood from gymnosperm trees such as conifers. The term is opposed to hardwood, which is the wood from angiosperm trees. The main diff ...
and hardwood
Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
chemical pulps are used and a minor part of mechanical pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemical or plant-based additives, pulp is the major raw mate ...
might be added (often of aspen
Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section ''Populus'', of the ''Populus'' genus.
Species
These species are called aspens:
*'' Populus adenopoda'' – Chinese aspen (China ...
or poplar). These paper grades are calendered.
Properties
Woodfree uncoated papers are of high quality and have a natural look and feel. The properties are good strength, high brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...
and good archival characteristics. They provide a non-glare surface suitable for reading and writing.
Special types
''Offset paper'' is a WFU paper with ISO brightness > 80% and a basis weight of 40–300 g/m2. Surface strength and low linting are the main parameters, but brightness and opacity are also important.
''Lightweight offset paper'', also called onionskin
Onionskin or onion skin is a thin, lightweight, strong, often translucent paper. Though not made from onions, it superficially resembles their thin, papery skins. It was usually used with carbon paper for typing duplicates in a typewriter, for ...
, has a basis weight of 25–40 g/m2 and are normally used for bible
The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts of a ...
s (hence the name Bible paper
Bible paper, also known as scritta paper, is a thin grade of paper used for printing books which have many pages, such as a dictionary. Technically, Bible paper is a type of woodfree uncoated paper. This paper grade often contains cotton or line ...
) and dictionaries
A dictionary is a listing of lexemes from the lexicon of one or more specific languages, often arranged alphabetically (or by radical and stroke for ideographic languages), which may include information on definitions, usage, etymologies, p ...
.
References
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Paper