Paper Technology Journal 19 - Voith

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Fig. 4: Paper destroyed by acids.
Fig. 5: Mold damage.
Fig. 6: Damage caused by aggressive inks.
Fig. 7: An extensively damaged map.
Acid damage to paper – the
biggest problem and challenge
Books are part of our cultural heritage,
but are exposed to many different dangers.
The worst of these are not bookworms,
bark beetles or other destructive
insects, nor even mold or similar problems
caused by incorrect handling of
valuable volumes. If asked about the
main priorities in the preservation of old
books, Dr. Manfred Anders, the ZFB’s
General Manager, is sure that the main
challenge for the future will be to stop
acid decay, which according to current
knowledge threatens at least two-thirds
of the world’s most significant libraries,
archives and document collections.
The acids that cause this damage often
enter the paper in the fillers or as a result
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ZFB document restoration techniques:
Fig. 8: Bulk deacidification, in which the books
are soaked in a non-aqueous solution. A treatment
capacity of more than 100 tons a year.
Fig. 9: Aqueous fungicide treatment to eliminate
mold spores.
Fig. 10: Manual paper splitting.
Gelatin is used to hold the damaged document
between two supporting sheets of paper; it is then
split apart so that it can be stabilized by inserting
an interleaved core sheet between the two halves
of the original document.
of incorrect dosage of strengthening
agents during the papermaking process,
but environmental influences both past
and present are also to blame. The acids
break down the cellulose that provides
the paper with its mechanical strength,
whereupon it becomes brittle and breaks
up easily. This is an auto-catalytic ageing
process, in other words one that speeds
up automatically and can only be countered
by effective deacidification.
The ZFB, had its origin in the restoration
departments of two German libraries, the
‘Deutsche Bücherei’ and the ‘Deutsche
Bibliothek’, which were combined in
Leipzig following the German reunification.
For some time now it has confronted
this specific acid-damage problem and
developed equipment suitable for the
bulk deacidification of books. Such large-
Fig. 11: Mechanical paper splitting if the document
is less severely fragmented. In this case, a
thin but highly tear-resistant core sheet is inserted
between the two halves.
Fig. 12: Closing holes and gaps by mechanical
fiber reconstruction. As in papermaking, a fiber
suspension is applied to a screen in such a way
that the fibers take up the desired position and are
linked together.
Fig. 13: Restoring damaged book covers and
spines.
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scale methods are clearly essential if the
loss of possibly millions of important
books is to be avoided. In 1998 the ZFB
ceased to be part of the Deutsche Bibliothek
and became an autonomous institute.
With its know-how, its experience
and the methods at its disposal, it is today
in a position to assist all international
state-run and private bodies that have the
task of maintaining important collections
of books.
The ZFB’s ‘Papersave’ process
The books are pre-dried to reduce their
natural moisture content temporarily
from the usual 5-7% to below 1%. This
is followed by the actual deacidification
process, in which the books are soaked
in an alkaline, non-aqueous solution. For
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