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This information is reprinted from the For Beginners column
of Hand Papermaking Newsletter #38 (April, 1997).
To learn how to order Hand Papermaking bi-annual magazine
and quarterly newsletter, click
here.
Sizing
The basic ingredient of handmade paper is plant cellulose,
which is hydrophilic--it loves water. This is an advantageous
quality while paper is being made, but can lead to unfortunate
consequences after the paper is made. The extreme porosity
of an untreated sheet of paper means that printing or drawing
inks and water-based dyes will soak into the paper spreading
quickly and randomly. Sizing the paper will reduce or eliminate
this bleeding and feathering by encasing the cellulose fibers.
As an added benefit, sizing protects the fibers from breakdown
due to oxidation. In addition, since other commonly used
fillers can inhibit bonding between fibers thereby weakening
the sheet, sizing can have adhesive qualities and add strength.
Papermakers in the East used various starches to size their
paper. Up until recently, Western papermakers used alum
and rosin, which are highly acidic. And prior to that, they
made a gelatin size by boiling down the remains of slaughtered
animals. Luckily for us, improved methods have developed
since.
While one can make natural starches from potatoes, rice,
or gelatin, it is more common and easier to simply purchase
chemical sizing from papermaking suppliers.
Sizing is added directly to the vat (internal) or applied
to the sheets after formation (external). Both methods have
their benefits, and some papermakers even use a combination
of both techniques.
Internal sizing is an easy way to apply a coating to individual
fibers, but still allow for some absorption of oil or water
based ink or dye. All the paper made from one batch of pulp
is equally sized.
External sizing is more time consuming, but has some advantages.
Individual sheets can be sized differently, for instance,
if destined for different uses. Surface sizes do not envelop
individual fibers but add a protective coating to the sheet
itself, inhibiting any absorption or bleeding. While this
is a helpful quality for calligraphers, some do not care
for the appearance of handmade sheets with too much surface
sizing.
Apply external sizing to well-dried paper using one of
three methods: painting, spraying, or tub sizing. Use a
large soft brush for quick application, or a simple plant
sprayer if the size is fairly thin so as not to clog the
sprayer. Or, run dry sheets through a tray of sizing liquid,
or soak them in the tray for several minutes followed by
a light pressing.
Personal experimentation is the key to successful sizing
in your own studio.
Copyright 1997 Hand Papermaking, Inc.
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