CG members have been introduced to the colouring of aluminium and titanium in previous meetings. This meeting considers the colour of metals more traditionally used for jewellery and decorative metalwork.

Mark Grimwade Colours of the Precious Metals, Copper and their Alloys

Why are gold and copper the only truly coloured metals and why is silver the most brilliantly white of all metals? Mark will introduce the scientific explanation for the relationship between reflectivity and wavelength in the visible light spectrum. He will give examples of how alloying affects the colour of these metals, particularly for the carat gold alloys and copper alloys.  He will also discuss methods for assessing colour, e.g. the CIELAB system for measuring colour space coordinates.

Helena Tellez Lozano The study of blue patinas on steels (A multi-analytical approach)

Patination of metals has been used for decorative or protective purposes for centuries and several methods to create coloured films on metal surfaces have been developed. Helena will describe a multi-analytical approach to characterize artificial blue patinas created on mild steel substrates by means of traditional recipes and methods for colouring ancient objects and artefacts. The combined use of secondary ion mass spectrometry (SIMS), focused ion beam (FIB), X-ray diffraction spectroscopy (XRD), white light interferometry and reflectance spectroscopy allows to characterize blue patinas on steel substrates and to investigate the relationship between the developed color and the patina layer microstructure and composition. Therefore, the analysis of the oxide films produced by either thermal or chemical coloring methods has been successfully performed, providing information about the film morphology, the surface composition and in-depth elemental distribution within the colored layers, and the origin of the color developed on the surface.

Coilin O'Dubhghaill Irogane, a search for reliability between craft & science

The Western tradition of metal patination and colouring is based on the use of a small range of metals and alloys which are coloured by the application of a wide range of patination solutions. In contrast to this, Japanese metalworkers developed a wide range of irogane alloys which are coloured with a single (niiro) patination solution. This approach allows different alloys to be combined in one piece and patinated, producing a multi-coloured piece of metalwork. Coilin will present the results of his three year project in Japan focusing on Japanese alloys and patination, and the effect that this research has had on the craft practice and scientific practice of the researchers involved.

Trish Woods The patination of pewter
The patination of metals has a long well documented history which has mainly centred on colouration techniques for copper and copper based alloys. However the colouration of pewter and its primary alloy tin has been largely ignored. Some evidence exists regarding the use of anodisation as a colouring method but these are limited and never extensively developed. As a result I have been engaged in research that explores the possibilities for colouring tin and specifically chemical based processes for colouring pewter. The aim of the research was to establish a safe and effective process that may be utilized by craftsmen and industry alike. This presentation will discuss the research that has taken place, the results of that research and possibilities for future exploitation.