Lichte Nacht der Iris

The Rainbow’s Missing Colours

INGO NUSSBAUMER / 2021

Light installation showing the normal and the inverted solar spectrum.
With a heliostat, directed sunlight, a water prism, light-guiding stencils, and a stainless steel shadow-caster.

In ancient times, the rainbow was considered a symbol of Iris, the messenger of the gods. In a dark environment, its colours can be conjured from sunlight that falls through a prism and a narrow slit. When Newton made this discovery in 1666, he laid the foundation for modern optics. A lesser-known fact is that this experiment can be inverted. If sunlight falls through a prism and across a dark bar in a light environment, it creates a spectrum of complementary colours. Goethe called attention to this inverted experiment and used it to challenge Newton’s experimental arrangement. The Newtonian spectrum received its spectral counterpart: the Goethean spectrum.

The artist Ingo Nussbaumer has been working with both spectra in his light installations for years. For the first time ever, he now presents both simultaneously at the Deutsches Romantik-Museum on an unprecedented scale. First, sunlight passes through a large water prism. In a Newtonian manner, it is directed through a slit on the right and split into the bold colours of the rainbow: red, green, and bluish violet. On the left, a shadow-caster transforms the darkness behind the prism into a radiant night image of luminous turquoise, purple, and lemon yellow. The spectra are only visible in favourable weather and solar conditions.