“Reconstructing” a colour theory: Unraveling the theoretical, material and methodological assumptions underlying James Sowerby’s "A New Elucidation of Colours" (1809)

Abstract

The mineralogist, botanist and engraver James Sowerby (1757 - 1822) is known for his high-quality illustrations of natural history works. Some 15 years after the publication of the coloured engravings for his "British Mineralogy", he discovered that many of the pigments used had become discoloured. In 1809 he published "A New Elucidation of Colours", in which he introduced his solution for the arisen problem. Building on the work of Sir Isaac Newton, Sowerby proposed using the colours created when light is refracted through a prism as a guide, since light cannot discolour. In my thesis, I perform an in-depth study of Sowerby’s method to generate colours out of light with a device named a “chromatometer”, adopting an interdisciplinary approach to elucidate Sowerby’s work: I integrate philosophical concepts, reconstructions, colorimetric analyses and a participant study. In chapter one, I investigate which theoretical explanations Sowerby provides regarding the colours observable in nature and during experiments. To make Sowerby’s theoretical assumptions explicit, I compare them with observations of Newton and Goethe. The comparison shows the fundamental difference between their theories, and that these theoretical differences caused them to report different colours when studying the same phenomena. I argue that Sowerby’s dual nature as an artist and natural philosopher enabled him to create his theory in which material colours could be equated to prismatic colours. It then becomes comprehensible, that the lengthy expose Sowerby provides in his "Elucidation" (before he explains the working of the chromatometer) is put in place for a purpose: to convince people working with pigments that they could safely transfer to his chromatometer method based on prismatic colours. In chapter two, I investigate the materials that are necessary for the creation of a chromatometer and colours upon it: paper, pigment and a prism. The contrast between the whiteness of paper and the blackness of the patches painted upon it are essential to create colours in different tints. But what materials were available to contemporaries of Sowerby, to create this contrast on a chromatometer? Would variations in the used materials compromise Sowerby’s aim at universal communication about colours? How would various types of glass prisms influence what people might perceive? Comparing these material aspects with the extent to which Sowerby paid attention to them, and embedding these findings within larger debates about the properties of these materials at the time, enables me to make Sowerby’s material assumptions explicit. In chapter three, I investigate to what extent human perception and the ability to execute Sowerby’s method influence people’s observations. I asked participants to code and decode colours with Sowerby’s method. Since other scholars stressed the difficulty of his method, I introduced the participants to Sowerby’s theoretical and methodological assumptions in a teaching trajectory, based on some of Sowerby’s preliminary experiments. Besides studying the teachability of his method, I put Sowerby’s claim of universal communicability to the test: do all participants indeed provide the same measured values when naming the same hues of colours? Or do differences in skill for using Sowerby’s method, and/or physiological differences between individuals cause varying results? In the conclusion, I synthesise how the studies in the three chapters informed us about the theoretical, material and methodological assumptions underlying Sowerby’s Elucidation. Although the Elucidation might seem elusive, by making Sowerby’s ideas explicit, I show that Sowerby’s text is founded on a plethora of theoretical, material and methodological assumptions, that together form a remarkable theory of colour.