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This information is reprinted from the For Beginners column
of Hand Papermaking Newsletter #18 (April, 1992).
To learn how to subscribe to Hand Papermaking's bi-annual
magazine and quarterly newsletter,
click here.
Common Additives
While some may think that the best paper comes from the
vats containing only pulped fiber and water, there are many
beneficial chemical additives which are used in hand papermaking.
These materials are added to the pulp either during the
mixing stage or in the vat itself before sheet forming.
For Japanese nagashizuki papermaking, an essential additive
is neri, which is used to slow drainage through the screen.
It is known as a formation aid or deflocculant. The Japanese
pound the roots of the tororo aoi plant (a member of the
hibiscus family) to form this viscous liquid. Other natural
sources of formation aid have been used in Chinese and Korean
papermaking, and okra and similar substitutes are used by
some Western papermakers.
Synthetic formation aids are used more frequently now,
especially PNS and PMP, as tororo aoi in particular does
not store well and is hard to come by. In recent years,
papermakers have experimented using formation aid with Western-style
sheet forming to achieve various decorative effects. The
most traditional additives in Western papermaking (ignoring
bleaching agents, which are used to whiten fibers but are
then rinsed out before sheets are formed) are sizes. These
inhibit the water-loving qualities of the fiber in paper
so that writing or painting on the paper does not feather
and bleed. While the oldest sizes were made of gelatin into
which dried paper is dipped, sizes added to the vat, know
as internal sizes, were developed in the late 18th century
as time-savers and soon replaced gelatin sizing as machine
papermaking took hold.
Various kinds of size have been developed for different
qualities of paper. Alum rosin sizing was used extensively
for both hand- and machine-made paper. Unfortunately this
size, while economical and much easier to use that gelatin,
creates paper which is usually acidic.
Many of the books produced since the early 19th century
are now rapidly decaying because the paper has become so
brittle. Most machine papermakers are now turning toward
sizes which help produce paper in a more neutral pH range.
The synthetic sizings most hand papermakers use today are
also less acidic or can be used with other additives which
neutralize the acidity.
Colored paper can be made from colored rags, but most
hand papermakers use dyes or pigments to change the color
of a pulp. There are many different ways to color fiber
and many variables involved in selecting the best method
for a particular fiber and desired effect. In general, colorants
are mixed in with pulp before it is added to the vat. Most
pigments require an additive called a retention aid or agent
to help them adhere to the fiber.
Other additives used in hand papermaking include fillers
and whiteners. Fillers occupy some of the gaps between fibers
in paper and make the paper somewhat dense and more opaque.
They may also serve as buffering agents to make paper less
acidic. Calcium carbonate and magnesium carbonate are the
most commonly used fillers. Whiteners, like titanium oxide,
also end up in the spaces between fibers, but their specific
purpose is to create a brighter finished sheet. Because
both of these types of additives may inhibit fiber-to-fiber
bonding, they may diminish the strength of paper made from
pulp to which they have been added.
While most paper fibers are benign in their health effects,
many chemical additives are not. Powdered pigments, in particular,
can be quite toxic and, once airborne, are easily inhaled.
Many additives are poisonous if ingested. Certain ones can
also cause rashes and other skin reaction on hands and arms
dipped into the vat. Precautions are, therefore, urged in
dealing with all of these chemicals: good ventilation and
masks are recommended when using powdered pigments; gloves
or the use of a skin guard may be appropriate to avoid contact
sensitivity.
Because of the variety of additives available, the hand
papermaker is urged to research the subject carefully. Further
reading is recommended.
Copyright 1992 Hand Papermaking, Inc.
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