Minerals associated with artists' paintings and archaeological iron objects

This article provides a short review of mineral-based pigments used in paintings with examples drawn from technical studies of selected historic paintings. Pigments such as azurite, natural ultramarine, orpiment, and clay earth pigments have been identified. Some examples will also be given of particular case studies which describe the alteration of selected pigments and consequences of these interactions. The second theme shows how use has been made of such interactions in evaluating the effects of environmental impact on paintings and reference is made to previous studies and the application of paint films as dosimeters. Accelerated ageing and site exposure studies are reported, and results provide information on pigment binder interactions. Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TG) have been used to characterise the behaviour of pigments in binding media and to assist in characterising samples from wall paintings. Reference is also made to the occurrence of iron-oxide based minerals present as corrosion products in archaeological iron objects. Examples are given of objects from two archaeological sites in England, the Anglo-Saxon burial site Sutton Hoo in Suffolk, and the burial site in Wetwang, East Yorkshire. It will be shown that post excavation changes occur in the objects and this information is used to inform preventive conservation of these objects, in storage and in display.