Turner used this diagram in a lecture on perspective. He wanted to show his students how to use colour to create the illusion of depth in a flat painting. Using the three primaries, he shows how the colours in light behave when they are represented in watercolour materials. Blue and red stand for degrees of shade, while yellow suggests light itself. Turners use of the colour circle is a reference to Goethes Theory of Colours
Venice by day was transformed by its unique combination of light and water. Turner used white paper to enhance the clarity of his transparent watercolour washes. His Venetian watercolours are saturated with warm yellows and browns and limpid green or blue to suggest the dazzling intensity of the sun and a sense of healthy serenity.
Turner relished the Sublime effects of darkness. Its mysterious and elusive charm could stir the emotions in passionate and disquieting ways, for example in his night-time scenes of Venice. While for Newton and Goethe darkness was merely a negation of light, Turner expressed it positively in his works using colour. Intense, matt pigments applied to paper with a reddish ground could be dramatically offset by touches of bright white.
The ark stood firm on Ararat; threturning sun Exhaled earths humid bubbles, and emulous of light, Reflected her lost forms, each in prismatic guise Hopes harbinger, ephemeral as the summer fly Which rises, flits, expands, and dies.
This is a verse from Turners poem, The Fallacies of Hope. The lines accompanied Turners painting Light and Colour (Goethes Theory) – the Morning after the Deluge – Moses Writing the Book of Genesis and drew upon Goethes ideas of the prismatic colour visible in bubbles and the symbolic associations of colours.
(To learn more about this work you can watch Cecilia Powells film about Turners paintings responding to Goethe in this room of the exhibition.)