In transparent glass, colour occurs through the absorption of certain wavelengths of light, and transmission of other wavelengths. In thicker sections of glass, more light is absorbed than in thinner sections, making the thicker sections appear darker, and sometimes a different hue. This
phenomenon is called volume colour by Joseph Albers, and together with the optical properties of glass as a denser material than air, leads to remarkable possibilities for glass artists, to work with form to achieve light accents
and/or different hues in solid object made from a single transparent glass colour. Artists in the Czech republic have explored this potential in cast glass since the 1960s, working directly with colour factories, and passing on
gained knowledge through teaching. Elsewhere, it is difficult for artists to explore these possibilities for two reasons: Firstly, the lack of literature on
volume colour, and the difficulty of translating theoretical information on optics into practical application. Secondly, on the practical side, it is unusual
for artists to work with factories to develop their glass colours. Instead, colours are available in a limited range of hues, and casting colours are developed for small to medium sized objects around 5 cm thickness, therefore often appear very dark or black when used for larger solid casts of more than 10 cm thickness. To explore the relationship between colour, form and light in glass sculpture, artists need to be in control of colour hue and value. To achieve control, they have to either work with a factory, or colour their own glass. This research contributes to the practice of kiln casting
through the development of methods to produce homogenous transparent colours in a studio environment, using ceramic crucibles in a kiln. Visual and written guidelines about basic colour results using single colouring agents
provide a starting point for development of bespoke hues and densities. Drawing on physics texts and through a thorough study of existing glass sculpture, the optical properties of glass are explained in relation to practical
application.