title: New insights into the ageing of linseed oil paint binder: a qualitative and quantitative analytical study.
abstract: This paper presents an analytical investigation of paint reconstructions prepared with linseed oil that have undergone typical 19th century treatments in preparation for painting. The oil was mechanically extracted from the same seed lot, which was then processed by various methods: water washing, heat treatments, and the addition of driers, with and without heat. A modern process lead white (Dutch source, Schoonhoven) and a commercially available vine black were used as pigments. The reconstructions were prepared in 1999, and naturally aged from then onwards. We compared thermogravimetric analysis (TG), which yields macromolecular information, with gas chromatography-mass spectrometry (GC-MS) and direct exposure mass spectrometry (DEMS), which both provide molecular information. The study enabled us to quantitatively demonstrate, for the first time, that the parameters used to identify drying oils are deeply influenced by the history of the paint. In particular, here we show that the ratio between the relative amounts of palmitic and stearic acid (P/S), which is used as an index for differentiating between drying oils, is extremely dependent on the pigments present and the age of the paint. Moreover the study revealed that neither the P/S parameter nor the ratios between the relative amounts of the various dicarboxylic acids (azelaic over suberic and azelaic over sebacic) can be used to trace the sorts of pre-treatment undergone by the oil investigated in this study. The final results represent an important milestone for the scientific community working in the field, highlighting that further research is still necessary to solve the identification of drying oils in works of art.
authors.affiliation: Dipartimento di Chimica e Chimica Ind., Università di Pisa, Pisa, Italy. ilariab@dcci.unipi.it
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bonaduce
authors.forename: Leslie
authors.initials: L
authors.lastname: Carlyle
authors.forename: Maria Perla
authors.initials: MP
authors.lastname: Colombini
authors.forename: Celia
authors.initials: C
authors.lastname: Duce
authors.forename: Carlo
authors.initials: C
authors.lastname: Ferrari
authors.forename: Erika
authors.initials: E
authors.lastname: Ribechini
authors.forename: Paola
authors.initials: P
authors.lastname: Selleri
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Tiné
mesh_terms: D000367:Age Factors; D004396:Coloring Agents / Q000737:chemistry*; D003998:Dicarboxylic Acids / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D049672:History, 19th Century; D058427:Hygroscopic Agents / Q000032:analysis* / Q000737:chemistry; D008043:Linseed Oil / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D010150:Paint / Q000032:analysis*; D010151:Paintings / Q000266:history*; D010169:Palmitic Acids / Q000032:analysis; D013229:Stearic Acids / Q000032:analysis; D013818:Thermogravimetry
chemical_list: D004396:Coloring Agents; D003998:Dicarboxylic Acids; D058427:Hygroscopic Agents; D010169:Palmitic Acids; D013229:Stearic Acids; C031183:stearic acid; D008043:Linseed Oil