Paper Conservation: Decisions & Compromises

Fig. 2: detail with losses and loose pigment flakes (raking light)
Fig. 3: feathered hinges attached along the edge on the verso of a painting
Besides the visually disturbing “plastic feeling”
within the shiny polyester pockets, the current
problems of the paintings include their sliding
within the partially creased pockets when turning
pages (Fig. 1). Abrasion occurs as well as static
charges which endanger loose pigments (Fig. 2).
Some of the tapes’ adhesive has migrated into
the supporting paper, some of the carriers have
fallen off.
The range of possible conservation interventions
to secure the condition of the Croÿ-Albums included
doing nothing (leading to denying access
to the objects for readers), minimal intervention
(replacing the pressure sensitive tapes), as well
as an overall treatment (remounting the parchments
within the Baroque bindings). The extreme
intervention considered was to remove the
paintings from the books and to re-house them
in individual double-sided matboards stored in
acid-free boxes.
Creating a decision-making tree helped to visualize
the complexity of the issues involved and
to better understand common points and differences
between the various options. The treatments’
impacts were discussed considering the
factors of safety for the objects, practical feasibility,
time (labour costs, balancing priority with
other projects), material costs (custom-made rag
paper for frames, Japanese paper for protective
sheets, archival quality matboards) as well as
a possible increased need of storage space. The
common requirements for the time-consuming
invasive interventions (remounting or removing
from the bindings) were the consolidation of
the flaking paint layers, and to ensure safe handling
of the objects in order to allow a careful
although restricted use of the valuable paintings.
Some of the theoretical treatment options, like
remounting each parchment in a paper frame
reflecting the Baroque mounting, were ruled out
after evaluating the results of practical tests and
mock-ups.
Considering the importance of the Croÿalbums,
a cost- and time-intensive overall treatment
seemed justified. Finally, the choice was
made to remove the polyester pockets from the
books and to attach the consolidated parchments
with adapted T-hinges to the supporting
paper pages.
A few paintings with very fragile paint layers
and heavy pigment losses will not be remounted
into the books but kept separately in doublesided
matboards.
The estimated timeframe per treated volume
is roughly 300 working hours.
A positive side-effect of this long-term project,
during which each of the parchments needs to
be handled, is the chance to digitize the paintings
after consolidation before remounting. The
availability of high quality digital images facilitates
access to the content of the valuable miniatures.
At the same time it permits to strictly limit
the physical use of the fragile originals.
For areas with poor adhesion, consolidation is realised
with gelatine 1% w/v in water (Gelita Novotec
GP Type 73 189 technical grade, type B) using
an ultrasonic mister (AGS 2000, ZFB). For flaking
areas the gelatine is applied 2% w/v with a thin,
long-hair brush (5/0 da Vinci, Nova Synthetics).
Hinges of Japanese paper (Paper Nao RK-38, 16g/
m², 3 x 2 cm) are attached along the left edge
on the back of the treated parchment using a
mixture of wheat starch paste and Methocel
A4M 2.5% w/v (spacing 0.7 cm) (Fig. 3). A sheet of
strong, yet smooth and slightly translucent Japanese
paper (Paper Nao RK-19, 32g/m², 59 x 46.5
ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013
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