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This information is reprinted from the For Beginners column
of Hand Papermaking Newsletter #37 (January, 1997).
To learn how to order Hand Papermaking bi-annual magazine
and quarterly newsletter, click
here.
Archival Paper
Anyone who has unfolded an old newspaper clipping from
memorabilia knows the importance of making paper to an archival
standard. Newspaper, for instance, will become a brittle
and discolored artifact in a very short time as a result
of acids which remain in the paper when it is made. Acid-free
paper, by contrast, is a permanent and relatively stable
legacy for future generations to enjoy.
Papermakers rely on a measurement known as pH to determine
if pulp is too acidic or too alkaline. The pH scale is a
span of numbers from 0-14. The lowest numbers are most acidic,
the highest numbers are most alkaline, and 7 is considered
neutral. The pH level is easily tested with a color-changing
test strip available from papermaking suppliers (also available
where aquarium or pool supplies are sold).
Since we all live in an atmosphere that is slightly acidic,
it is best to counter with pulp that is slightly alkaline--say
8 or 9--rather than neutral. Calcium carbonate, an alkaline
buffer, can be added to adjust pH level; it also acts as
a filler to make the paper more opaque. Plant fibers are
often cooked in soda ash which is strongly alkaline and
the resulting pulp must be rinsed well to bring the pH down
closer to neutral.
There are other extraneous materials (sugars, starches,
gums, etc.) that will cause discoloring and deterioration
if not removed during cooking. Lignin, part of the plant
cell wall, not only impedes bonding but can also be a degrading
influence.
Once paper has been made to archival standards, it still
requires proper storage for permanence. The pH of wrapping
and packaging materials should be considered, and acid-free
storage boxes are a good investment.
Copyright 1997 Hand Papermaking, Inc.
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