Table 1. Scientific methods used Jor identification oj critical, unaltered parts oj a painting.
Method In ormation Li mitalJon
observatIOn under UV light I dark areas of repamlJng III - does not worK lor all
comparison wilh light areas binding media
of heavily oxidized oil paints - possible interference with
(autofluorescence) some varnishesUV photography documentation of repainted as above
areas
false color infrared identification of repainting if only for orientation, should
photography done using pigments of the be confirmed using other
same color but different methods of chemical
chemical composition analysis
X -ray radiography localization of support high contrast only for heavy
alterations, ground and paint chemical elements (Pb, Hg,
layer repairs and alterations Au)
X-ray f1uorescence - identification of repainted - possible difficulties with
spectrometry (XRF) areas if done with inorganic mixed pigments and
pigments of different complex multilayer paint
composi tion than original structure analysis
(e.g., zinc or titanium white - no analytical information
instead of lead white) for low atomic weight- a non contact analysis elements (Z :$ Na)
microchemIcal methods Identification of repainted - microsampling 01 paint
(polarized light microscopy, areas based on pigment material needed
chemical microscopy, identification - uncertain identification of
electron microprobe, X-ray some organic pigments and
diffraction) dyes
The visual traces left by the physical manipulation of painting materials on
paintings can be identified fo r study. Idiosyncrasies of color, brushwork, paint
consistency, fo rm, and so on can each be evaluated to reveal specific unique
qualities within given predefined techniques. This information can then be
used fo r the general analysis of historical paintings. The works of individual
artists can be analyzed in a similar manner, identifYing a signature style and
painting procedure through specifiC visual clues.The role of scientific and technical examinations
The process of applying scientific methodology to the study of painting tech
niques can be divided into the fo llowing three major steps: (1) identification
of the critical (unaltered) parts of the painting, (2) authentication of the paint
ing, and (3) study of detailed physical and chemical structure of paintings.
Identification oj the critical (u naltered) parts of the painting. The majority of paint
ings in museums or private collections have a long history of cleanings, res
torations, and alterations. Before embarking on a study of painting techniques,
it is essential to identifY areas of the painting in which the painting technique
of the original artist has not been altered by later treatments. Scientific meth
ods fo r such a study are described briefly in Table 1.
Authentication oj the painting. When a series of paintings by a particular artist
is examined with the goal of studying painting techniques, it is crucial that
the authorship of the pieces is established "beyond a reasonable doubt." Sci
entific research cannot establish the relationship between the artwork and the
artist. What scientific research can do very successfully is to effectively elim
inate paintings that, based on clearly defined scientific fa cts, could not have
been created during the active life of the artist in question. Several powerful
scientifiC methodologies that can be used to help authenticate paintings are
described in Table 2.
Study of detailed physical and chemical structure of paintings. Usually, only the top
paint layer, with its corresponding brushwork and surface treatment, is ac
cessible to visual observation. This is a very severe limitation when studying
painting techniques because before the alia prima technique became widely
used during the second half of the nineteenth century, the majority of paint
ings were created in complex multiple-step and multilayer processes. Table 3
shows several scientific methodologies that can be used in probing and ana
lyzing such painting structures.Barrett and Stulik 9