title: Determination of early warning signs for photocatalytic degradation of titanium white oil paints by means of surface analysis.
abstract: Titanium white (TiO2) has been widely used as a pigment in the 20th century. However, its most photocatalytic form (anatase) can cause severe degradation of the oil paint in which it is contained. UV light initiates TiO2-photocatalyzed processes in the paint film, degrading the oil binder into volatile components resulting in chalking of the paint. This will eventually lead to severe changes in the appearance of a painting. To date, limited examples of degraded works of art containing titanium white are known due to the relatively short existence of the paintings in question and the slow progress of the degradation process. However, UV light will inevitably cause degradation of paint in works of art containing photocatalytic titanium white. In this work, a method to detect early warning signs of photocatalytic degradation of unvarnished oil paint is proposed, using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Consequently, a four-stage degradation model was developed through in-depth study of TiO2-containing paint films in various stages of degradation. The XPS surface analysis proved very valuable for detecting early warning signs of paint degradation, whereas the AFM results provide additional confirmation and are in good agreement with bulk gloss reduction.
authors.affiliation: Rijksmuseum, Hobbemastraat 22, 1071 ZC Amsterdam, The Netherlands; Materials for Arts and Archeology, 3ME, TU Delft, Mekelweg 3, 2628 CD Delft, The Netherlands; Cultural heritage agency of the Netherlands, Hobbemastraat 22, 1071 ZC, Amsterdam, The Netherlands. Electronic address: b.van.driel@rijksmuseum.nl.
authors.forename: B A
authors.initials: BA
authors.lastname: van Driel
authors.affiliation: Catalysis Engineering, ChemE, TU Delft, Julianalaan 136, 2628 BL, Delft, The Netherlands. Electronic address: t.a.wezendonk@tudelft.nl.
authors.forename: T A
authors.initials: TA
authors.lastname: Wezendonk
authors.affiliation: Cultural heritage agency of the Netherlands, Hobbemastraat 22, 1071 ZC, Amsterdam, The Netherlands. Electronic address: k.van.den.berg@cultureelerfgoed.nl.
authors.forename: K J
authors.initials: KJ
authors.lastname: van den Berg
authors.affiliation: Catalysis Engineering, ChemE, TU Delft, Julianalaan 136, 2628 BL, Delft, The Netherlands. Electronic address: patricia.kooyman@uct.ac.za.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kooyman
authors.affiliation: Catalysis Engineering, ChemE, TU Delft, Julianalaan 136, 2628 BL, Delft, The Netherlands. Electronic address: j.gascon@tudelft.nl.
authors.forename: J
authors.initials: J
authors.lastname: Gascon
authors.affiliation: Materials for Arts and Archeology, 3ME, TU Delft, Mekelweg 3, 2628 CD Delft, The Netherlands. Electronic address: j.dik@tudelft.nl.
authors.forename: J
authors.initials: J
authors.lastname: Dik
keywords: Atomic force microscopy; Degradation; Oil paint; Photocatalysis; Titanium dioxide white; X-ray photoelectron spectroscopy