Paper

Paper is a thin, flat material produced by the compression of fibres. The
fibres used are usually natural and based upon cellulose. The most common
material is wood pulp from softwood trees such as pines, but other materials
including cotton (flax) and hemp may be used.

Manufacture

The paper making process has four simple steps:

Preparation of the fibres:

The material to be used for making the paper needs to be made into a
concentrated solution containing the fibres, called pulp. As many of these
fibres are derived from natural sources, this requires many stages of
separation and washing. Once the fibres have been extracted, they may also
be bleached or dyed to alter the appearance of the final product.

Forming into sheets:

The pulp now needs to be formed into the desired shape. This can be achieved
by a mould or by a continuous rolling process. A watermark may be impressed
into the paper at this stage of the process.

In the case of the mould process, a quantity of the pulp is placed into a
form, with a wire-mesh base (or other draining device), such that the fibres
are left coated on the mesh, and excess water can drain away. At this time
pressure may be applied to removed more water through a squeezing action.
The paper may then be removed from the mould, wet or dry, and go on to
further processing.

Modern, mass produced paper is made using a continuous rolling process. The
mould gauze is replaced with a gauze conveyor belt, and the paper is passed
through successive rollers that apply more and more pressure to remove the water.

Further additives:

Raw paper that contains only pressed and dried pulp is very absorbent (for
example, blotting paper), and does not provide a good surface upon which to
write or print. Thus, a huge variety of additives are employed to add
desired properties to the paper. These are applied in a coating called the size.

Sizing agents are often polymers designed to provide a better printing
surface. Starches are very commonly used, as is PVA, but there as many types
of polymer employed as there are types of paper.

Sizing agents can also seek to improve the printing surface by smoothing it.
The texture of raw paper is rough, and so to achieve greater smoothness, a
sizing agent such as clay is used. Smooth, matt finish papers such as
magazine paper (for the inside pages) are made in this way. The glossy
effect (for example on the covers of fashion magazines) is achieved at the
end of the printing process, by adding a clear layer (like varnish) over the
printing, and so is not a property of the paper.

Other additives are employed to enhance various properties of the paper, the
most common of which are optical brighteners.

Drying

The paper may actually be dried several times during its manufacture (dry
paper is much stronger than wet, so it is best to keep the paper dry to
prevent it breaking and stopping the production line).

Applications

   * to write or print on: the piece of paper becomes a document; this may
     be for keeping a record (or in the case of printing from a computer or
     copying from another paper: an additional record) and for
     communication; also a paper may represent a value:
        o bank note
        o check
        o security
        o voucher
        o ticket, e.g. for:
             + public transport or other bus trip, boat trip, etc.
             + movie theater
             + performance (unless it is one with voluntary contribution
               afterwards)
             + zoo
             + amusement park

     In such cases making a copy that can not easily be distinguished from
     the original should be very difficult, to avoid abuse, see counterfeit.

     official documents and private statements that are run through a
     computer are placed in individual letters by a "bursting machine".

   * for packaging
        o Wrapping tissue
        o Wallpaper
   * for cleaning:
        o toilet paper
        o handkerchiefs
        o miscellaneous cleaning in the kitchen, etc.

History

A form of paper called papyrus, made from reeds, was made as early as 3000
BC in ancient Egypt, and then in ancient Greece and ancient Rome. The modern
method of making paper from cotton rags was invented by Ts'ai Lun in AD 105.
The Chinese technology was first exported to Japan in 610, where fibres
(called bast) from the mulberry tree were used. From there the invention
spread to India, where it was copied by the Arabs, who took it to Italy in
about the 13th century.

Paper remained a luxury item through the centuries, until the advent of
steam-driven paper making machines in the 19th century, which could make
paper with wood fibres from wood pulp. Together with the invention of the
practical fountain pen and the mass produced pencil of the same period, and
in conjunction with the advent of the steam driven rotary printing press,
wood based paper caused a major transformation of the 19th century economy
and society in industrialized countries. Before this era a book or a
newspaper was a rare luxury object and illiteracy was the norm for the
majority of humanity. With the gradual introduction of cheap paper
schoolbooks, fiction, non-fiction and newspapers became slowly available to
nearly all the members of an industrial society. Cheap wood based paper also
meant that keeping personal diaries or writing letters ceased to be reserved
to a privileged few in those same societies. The office worker or the
white-collar worker was slowly born of this transformation, which can be
considered as a part of the industrial revolution and all of its phases.