Paper Conservation: Decisions & Compromises

had been used, may be false-positive as these
substances are good dye absorbents. Due to the
limitations of the methods, it was necessary to
perform further identification by using FTIR
analysis. The first samples were obtained using
swabs soaked in water, which allowed for selective
isolation of substances which are the most
water-soluble – plant gums, which also constitute
the object’s top layer. It is probably the layer
with which the object was coated in its entirety
during conservation works in the 50s. The comparison
of the obtained spectra with the spectra
for substances in standard samples taken with
a scalpel (Fig.1.I-III) provided a probable picture
of animal glue content with a small addition of
plant gums.
In order to preliminarily establish the scope of
work, non-destructive studies were carried out by
using false-colour infrared photography. The difference
between the infrared image (in the range
of 500-900 nm) and a part of the visible spectrum
indicated the presence of specific pigments
(Fig.1.12-18). Prussian blue, ferrite and organic
yellow as well as cinnabar were identified. Further
studies were recommended, that were based
on reflected-light microscope observation, water
smears viewed in transmitted light, microcrystalline
and drop reactions to test the presence of
selected inorganic ions as well as analysis of the
elemental composition of samples performed
using the scanning electron microscope. Raman
spectroscopy also proved useful. Eleven pigments
were identified (Fig.1.1-11), three of which will be
described in more detail.
Blue pigment showed up as very small particle
groupings in cloudy, greenish blue areas. The
pigment was base-sensitive and it vanished after
adding a base solution. Ferric ions were present
in the obtained solution. This means that Prussian
blue had been used. Prussian blue was identified
both in the Chinese image and European
border (Fig.1.11). This pigment was obtained in
1704. After 1750 it was brought to China by the
East India Company. After 1825 it was produced
in Canton.
Red pigment showed high resistance to acid
and base reagents. No solubility was observed. A
very distinctive microscopic view revealed large,
angular and intense red grains. Characteristic
parallel striations were observed among the red
grains of natural cinnabar. Cinnabar was identified
in the border and the image’s part depicting
the boy’s attire (Fig.1.5). It is a natural pigment
Fig. 2: A woman under a blossoming tree, Wilanow Palace
Museum, photo by T. Rizov-Ciechanski
obtained by grinding the mineral and it was
used in the ancient China as early as in the sixth
and fifth century BC. It is called zhu sha. Rich cinnabar
deposits are located in southern Chinese
provinces. The method of manufacturing its
artificial form, that is dry-process vermilion – yin
zhu, was also developed in China at the beginning
of our era.
Microscopic observation of whites from the
woman’s face suggested that there might be two
white pigments. Apart from very large, angular
and colourless grains, very small, non-characteristic
particles were observed as transmitting a
very small amount of light (Fig.1.6.a). The reaction
with diluted hydrochloric acid revealed partial
solubility. Some gas was released but a substantial
part of the sample was left intact. SEM-
EDS analysis (Fig.1.6.b) revealed mostly calcium,
carbon and oxygen, thus evidencing the presence
ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013
119