The Ins and Outs of 14 C Dating Lead White Paint for Artworks Application

Hendriks, Laura; Caseri, Walter; Ferreira, Ester S. B.; Scherrer, Nadim; Zumbühl, Stefan; Küffner, Markus; Hajdas, Irka; Wacker, Lukas; Synal, Hans-Arno; Günther, Detlef (2020). The Ins and Outs of 14 C Dating Lead White Paint for Artworks Application Analytical Chemistry, 92(11), pp. 7674-7682. ACS American Chemical Society 10.1021/acs.analchem.0c00530

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Lead white is known as one of the oldest pigments in art and can be used as a dating material. Upon production following the Stack process, the 14C isotope of atmospheric carbon dioxide is fixed in the carbonate, and its radiocarbon dating can be used as a proxy for the age of a painting. The previously reported carbonate hydrolysis protocol reaches its limitation when confronted with samples presenting a mixture of carbonates, such as lead carbonate (cerussite or hydrocerussite), calcium carbonate (calcite), and/or calcium magnesium carbonate (dolomite). Thermogravimetric analyses indicate that decomposition of lead carbonate can be achieved at 350 °C in TGA diagrams, as other mineral carbonates only decompose to carbon dioxide at temperatures above 700 °C. Thus, a thermal approach is proposed to separate the various carbonates and isolate the specific 14C signature to the lead carbonate. In practice, however, discrepancies between the measured radiocarbon ages and expected ages were observed. FTIR analyses pointed to the formation of metal carboxylates, an indicator that the organic binder is not inert and plays a role in the dating strategy. Upon drying, oxidation and hydrolysis take place leading to the formation of free fatty acids, which in turn interact with the different carbonates upon heating. Their removal was achieved by introduction of a solvent extraction step prior to the thermal treatment, which was confirmed by GC-MS analyses, and thus, the collected carbon dioxide at 350 °C results can be assigned correctly to the decomposition of the lead white pigment. The proposed procedure was furthermore verified on mixed carbonate-bearing paint samples collected from a Baroque oil painting.

Item Type:	Journal Article (Original Article)
Division/Institute:	Bern Academy of the Arts Bern Academy of the Arts > Institute Materiality in Art and Culture Bern Academy of the Arts > HKB Teaching Bern Academy of the Arts > Institute Materiality in Art and Culture > Material analyses
Name:	Hendriks, Laura; Caseri, Walter; Ferreira, Ester S. B.; Scherrer, Nadim0000-0002-6576-885X; Zumbühl, Stefan0000-0002-8896-2938; Küffner, Markus; Hajdas, Irka; Wacker, Lukas; Synal, Hans-Arno and Günther, Detlef
Subjects:	N Fine Arts > ND Painting Q Science > QC Physics
ISSN:	0003-2700
Publisher:	ACS American Chemical Society
Language:	English
Submitter:	Nadim Scherrer
Date Deposited:	22 Jun 2020 07:54
Last Modified:	18 Dec 2020 13:30
Publisher DOI:	10.1021/acs.analchem.0c00530
ARBOR DOI:	10.24451/arbor.11876
URI:	https://arbor.bfh.ch/id/eprint/11876