alchemy of color
Authors: Flór Olga , Chomaz Jean-Marc ,   École nationale supérieure des Arts Décoratifs Paris
Published: October 2024

Alchemy of Color: Enlightening Nanoworlds is a research/creation project designed to challenge the certitudes of our perception, by presenting gold and silver objects sculpted at a nanoscale, invisible to all optical processes. The result is two complementary installations: A Thousand Shades of Green, an Attempt - nanolithographies, a nanoengraving on a glass disk, and Alchimie de la lumière - nanosculptures.

Coloring is an artistic gesture, a sensitive use of light associated with human visual perception. But coloring is also a physicochemical process associated with the interaction between photons and the molecular matter of pigments and inks. The colors of nanoparticles are a consequence of another light and matter interaction. Smaller than the photons that strike them, the metal nanosculptures are electrified and deflect the rainbow's path. Here, color is no longer a molecular property of light absorption by pigments or dyes but a resonance that makes form tangible. This photonic resonance of light with nanoscale textures belongs to the family of structural coloration. It differs from the latter through interferences that occurs when the object is larger, a fraction of a micron in size, about half the photon's wavelength. Classical pigments absorb light, as do plants: they appear green since the chlorophyl absorbs the blue and the red of the visible spectrum.

One of alchemy's ancient goals was to transmute matter, lead into gold, copper into silver. In the present project, the nanoscale sculptures that interfere with light are made of gold and silver and the alchemy refers here to the transmutation of the photons into plasmon. In an inversion of roles, invisible gold and silver objects are performing, in front of the spectator, the alchemical transformation of light, producing new colors, as if light and colors were matter.

A Thousand Shades of Green, an Attempt, is a nano engraving test using electronic lithography employing millions of gold cylinders, whose diameters increase from 50 to 100 nanometers, on a 2-square-centimeter glass disk. During the process, some parts of the metal layer deposited through the lithographic mask—too large for current technologies (limited to 1 square millimeter)—are torn away when the mask is peeled off. The damaged areas then reveal a world of iridescence, in green, orange, and blue.

The two installations, Alchimie de la lumière - nanosculptures, resemble cabinets of curiosity cabinet; they were created for the exhibition OU\/ERT in Bourges (2019) and Bourges contemporain in 2021. The glass forms, isolated or creating a landscape, change color according to the transformations of the light scene. The blown forms contain metallic nanoparticles, produced by chemical assembly, which emit a thousand new shades of green, depending on the angle that we look at it from. The aqueous nanoparticle solution thus appears green when seen in direct light and orange or blue in transparency.

Thus, the two installations constitute a modern form of vanities. In classical painting, earthly goods, money, scientific instruments, or symbols of knowledge were represented scattered or broken on the ground, alluding to their all being in vain with respect to a higher, inaccessible reality, a transcendence. Here, the nano engraving on the disk is broken and the perfect silver and gold nano spheres are invisible and only reveal their presence in the transformation of light into the multiple shades produced, the sensible dimension taking over the sensitive control.