heritage Article Multianalytical Assessment of Armour Paints—The Ageing Characteristics of Historic Drying Oil Varnish Paints for Protection of Steel and Iron Surfaces in Sweden Arja Källbom 1,*, Austin Nevin 2 and Francesca C. Izzo 3 1 Department of Conservation, University of Gothenburg, 40530 Gothenburg, Sweden 2 Courtauld Institute of Art, Somerset House, London WC2R ORN, UK;
[email protected] 3 Sciences and Technologies for the Conservation of Cultural Heritage, Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Via Torino 155/b, 30173 Venice, Italy;
[email protected] * Correspondence:
[email protected] Abstract: The characteristics of armour paints, historically used to protect ferrous industrial heritage, are explored. Amour paints contain lamellar and highly reflexive pigments of micaceous iron oxide (MIO) and metallic, leafing aluminium, bound in linseed oil and linseed oil–tung oil mixtures, on an inhibitive and soap-forming linseed oil primer (red lead). It is the first study of the binding media used for historical armour paints and investigates the chemical and physical ageing of armour paints using a multianalytical approach. Naturally aged examples are compared to accelerated aged replica armour paint, and to historical paints. The ageing and degradation reactions are assessed by complementary GC–MS and FTIR, together with measurements of wettability, hardness and surface colour. The historical paint formulations include linseed oils and alkyd binders. The results confirm Citation: Källbom, A.; Nevin, A.; Izzo, F.C. Multianalytical Assessment that the leafing effect of aluminium pigments results in only a small concentration of binder at the of Armour Paints—The Ageing surface: the paints studied reflect light and form a strong chemical and physical barrier.