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The explosion of
organic synthesis at the middle of XX century permitted the
introduction on the market of a wide range of new synthetic
molecules including organic pigments, thus enormously widening
the range of organic colouring materials available to artists
and manufacturers, with respect to the limited number of natural
dyes and lakes. Synthetic organic pigments are difficult to
distinguish and identify by analytical techniques, particularly
in complex matrices such as paint samples.
The DCCI-UniPI and CNR-Pg Unit, in collaboration with the Getty
Conservation Institute (LA, California), used Py-GC/MS, HPLC-DAD
and HPLC-ESI-Q-ToF and spectroscopic investigations for the
identification of organic synthetic pigments in paint materials.
76 synthetic pigments, 45 of them never previously reported as
being analysed by this technique, were characterised by Py-GC/MS
and classified in the following classes: metal complex,
β-naphthol pigment lakes, BONA pigment lakes, disazopyrazolone,
triarylcarbonium, dioxazine, anthraquinone, indanthrone,
isoindoline and thioindigo. This permitted to expand the data on
the naphthol AS, benzimidazolone, phthalocyanine and perylene
classes, with respect to the literature. An approach based on
HPLC allowed us to resolve complex mixtures of pigments also
when natural dyes are mixed with synthetic pigments.
The investigated case studies include artworks by Julian Schabel,
Keith haring, 20th century American artists, Clyfford Still
(1904-1980) and Jackson Pollock (1912-1956). The CNR-PG Unit
synthesised several eosinY lakes and used them to prepare
reference paint layers in linseed oil. The paint layers were
fully characterized by spectrophotometric techniques and
subjected to artificial ageing. DCCI focused on the
quantification of eosin in the different paint layers, before
and after ageing, and on the characterization of eosin
photo-degradation products.
Published papers
• Ghelardi E., A multi-analytical approach for the
characterization of contemporary paint materials, PhD Thesis,
2014, University of Florence.
• Ghelardi E., Degano I., Colombini M.P., Mazurek J., Schilling
M., Learner T. Py-GC/MS applied to the analysis of synthetic
organic pigments: characterization and identification in paint
samples, Analytical and Bioanalytical Chemistry, 2014, in press.
• Ghelardi E., Degano I., Modugno F., Colombini M.P. An
integrated approach to the study of Ri de Pomme, a painting by
Julian Schnabel, 2014, in preparation. |
