The School of Looking: INVISIBLE LIGHT | Spectral Tuning

Several years ago, following the death of British psychologist Richard Gregory, The School of Looking worked with Dr Patrick Cavanagh (Harvard University) on writing a programme to recreate some of Gregory’s experiments with the colour channels of a television set.

Richard Gregory (1923-2010), author of Eye and Brain: The Psychology of Seeing, thought that a television’s red, green and blue channels were comparable to the L, M, and S cones that capture colour in the eye. But he observed that the signal passing through the optic nerve appeared to be more complex, working with oppositions of blue/yellow, red/green and black/white.

© The School of Looking, The Animal Colour Debate (Dichromatic vision).

Spectral Tuning rewires the red, green and blue channels of a camera to explore this sort of oppositional colour matrix.

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The School of Looking: INVISIBLE LIGHT | Radio Hat Workshop

People have been building crystal radio receivers since the early days of radio. These devices need no external power and there is an enormous sculptural freedom in the way the coil, the capacitor and the antenna can be elaborated to tune into AM radio signals that can be listened to using earphones.

© The School of Looking, Radio Hat Workshop (detail), 2020.

Radio Hat Workshop is the result of a joyful experiment in marrying this technology with the art of millinery!

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The School of Looking: INVISIBLE LIGHT | Sacred Relic


The Cosmic Microwave Background is the oldest light in the universe. Once impossibly bright and hot, it has cooled to less than three degrees above absolute zero and faded to invisible microwaves. But it is still there –  a true relic of the beginning of the universe, perceptible to radio telescopes as a background to everything else we can see in the observable universe, the surface of a sphere that we observe from its very centre – a horizon that is the beginning of time and the end of space.

© The School of Looking, Sacred Relic (detail), 2020.

On 20 May 1964, Arno Penzias and Robert Woodrow Wilson – working with the newly contructed Holmdel horn antenna at Bell Laboratories in New Jersey, USA – recorded measurement of an excess 4.2K antenna temperature which they could not account for.

At first, Penzias and Wilson thought this might be an error, due perhaps to bird droppings on the surface of the dish. They went to Princeton University (less than 10 miles away) to consult with Robert Dicke, a leading cosmologist who was in the process of building a radio telescope to measure the Cosmic Microwave Background. Dicke immediately recognised the temperature they had measured as very close to what he had calculated he would find for the background temperature of the universe. Penzias and Wilson later received the Nobel Prize in Physics for their discovery.

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The School of Looking: INVISIBLE LIGHT | Made to Fade


In 1801, after hearing about William Herschel's discovery of "heat rays" (infrared radiation), physicist Johann Wilhelm Ritter (1776-1810) looked for an opposite (cooling) radiation at the other end of the visible spectrum.

Ritter did not find exactly what he expected to find, but after a series of attempts he noticed that silver chloride was transformed faster from white to black when it was placed at the dark region of the sun's spectrum, close to its violet end.

The "chemical rays" found by him were afterwards called ultraviolet radiation.

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The School of Looking: INVISIBLE LIGHT | The Sense of Heat


Things get hot when their molecules vibrate, and when they do, they give off electromagnetic radiation. The faster the molecules vibrate, the higher the frequency (and the shorter the wavelength) of that radiation.

The sun is very hot and emits high frequency radiation in the part of the spectrum that we can see. The molecules in our own bodies are lower in temperature and vibrate more slowly, giving off electromagnetic radiation mainly in the infrared region.

Infrared torso. © The School of Looking

When astronomer and composer William Herschel (1738-1822) discovered invisible light beyond the red end of the visible spectrum in 1800, he referred to it as “heat rays” because the instrument that detected it was a thermometer.

A thermal handprint. © The School of Looking.

We now have Infrared cameras that capture this invisible light and translate it into visible light. The resulting image may resemble what our eyes see in unfamiliar colours, but in fact it offers us sensory information unlike any that we have: a true sixth sense – heat vision!

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The School of Looking: INVISIBLE LIGHT | The Animal Colour Debate


Most mammals are dichromats, seeing two colours – blue and yellow – a simpler colour space than our own trichromatic vision, with its rich landscape of primary and secondary hues. But exactly what colours any animal can see will always be unknown unless we can find some way to ask them directly…

The School of Looking was introduced to a rich body of scientific research into animal vision by Dr Christoph Witzel (University of Southampton), who suggested some simple ways of interacting with animals through colour. The result was a series of simple, light-hearted experiments with many different animals involving illusions, coloured objects and coloured lights.

The famous ‘snake illusion’ was designed by Akiyoshi Kitaoka, a professor at Ritsumeikan University, Kyoto. Created with his kind permission, the floor of The Animal Colour Debate is a variation of Kitaoka’s illusion. Recently several researchers have observed – with surprise! – that cats respond strongly to the illusion, which prompted the artists to present it to some other animals and to capture their reactions on video.

© The School of Looking, The Animal Colour Debate (Snake Illusion Lino), 2020.
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The School of Looking: INVISIBLE LIGHT | UV tipi

UV TIPI: a contemplative environment of flourescent minerals, pigments and fabrics

Ultraviolet (UV) light is visible to some animals, in particular to foraging insects and birds. Should we then consider this light as colour? And is it possible for us to represent or even imagine colour that our own eyes have never seen?

Many freckles are only visible in UV. © The School of Looking.

There are cameras that can capture invisible colours and display them to us as visible colours, but a more natural form of translation is the fluorescence of materials that absorb UV and emit visible light.

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The School of Looking: INVISIBLE LIGHT | X Renaissance


Considered by artist and historian Giorgio Vasari (1511-1574) as one of the greatest Italian masters, Ercole de’ Roberti (c.1451-1486) is now almost forgotten as few of his works have survived.

Ercole de' Roberti, The Garden of Gethsemane, panel 35cm x 117cm. Staatliche Kunstsammlungen / Gemäldegalerie Alte Meister, Dresden. Restoration: Getty Conservation Institute.
XRF map of three elements in Ercole de' Roberti, The Garden of Gethsemane: Red pixels/Mercury (Hg)/Vermilion; Green pixels/copper (Cu)/copper-based pigment/s; Blue pixels/tin (Sn)/Lead-tin yellow.

The restoration of two of Ercole de' Roberti's panel paintings (pictured) – which are now preserved in Dresden and depict The Garden of Gethsemane and The Ascent to Calvary – reveals the magnificence of his art in all its vivid colour.

In 2019, Veronica Biolcati of Tyndall National Institute (Cork) worked at the J. Paul Getty Museum (Los Angeles) on the technical examination of the two panels. The study was done in view of their exhibition at the Getty to inform conservators, curators, art historians, and scientists themselves.

Both works were examined to address two main questions: what do the varnishes present on each panel tell us about the conservation history, and what does the palette of pigments tell us of the artist’s technique?

Ercole de' Roberti, The Ascent to Calvary, panel 35cm x 117cm, Staatliche Kunstsammlungen / Gemäldegalerie Alte Meister, Dresden. Restoration: Getty Conservation Institute.
XRF map of three elements in Ercole de' Roberti, The Ascent to Calvary: Red pixels/Mercury (Hg)/Vermilion; Green pixels/copper (Cu)/copper-based pigment/s; Blue pixels/tin (Sn)/Lead-tin yellow.

A series of non-invasive and micro-invasive analytical techniques were used, before and after the varnish removal. The conservation scientists used X-ray fluorescence (XRF) scanning, a non-invasive technique, to identify the rich array of materials that were on the artist’s palette in the late fifteenth century – pigments based on lead, copper, mercury, iron, gold, and many other elements.

The images also revealed pentimenti (underpaintings) and many other ‘lost’ details in the paintings. Another discovery, made by analysing a cross-section of a small painting sample, was a greyish toning layer covering much of the painting – with the notable exception of the figure of Christ – possibly applied during an early restoration. The natural ageing/yellowing of the varnish is one of the reasons the painting has become so dark. 

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The School of Looking: INVISIBLE LIGHT | See Through Me

SEE THROUGH ME: X rays collected to collage the human body from head to toe in transparency 

A conventional X-ray image is a black-and-white photographic film, which has been exposed to invisible light from a cathode tube emitting high energy, high frequency light that penetrates matter. Although these are negative images, they appear natural to us: white bone, dark tissue.

The School of Looking, I Can See Right Through You (detail), 2020, mixed media. © The School of Looking_
© The School of Looking, I Can See Right Through You (detail), 2020, mixed media.

See Through Me is the result of a collaborative project begun during lockdown in March 2020. Departing from the monochrome X-ray tradition, they are printed as duotones, using contrasting, complementary colours to create highly coloured prints that are neither negative nor positive.

With X rays kindly donated by of Aikaterini Christidou, Carmela Uranga, Erik Rehl, Ginette Moutounet, Hedi Sassi, Heidi Ellison, Helen Stokes, Inka Ernst, J. Kevin O’Regan, June McGrane, Kailani Dema, Lotti Connolly, Lucy Dixon, Marie Pierre Carnoy, Philippe Fernandez, Reine Melvin, Salammbo Connolly, Sebastien Gastine, Sophie Gorman Sassi, Susan Dunne, Thea McMillan.

A VISION REVOLUTION 2. Gamma & X rays (27’44”)

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The School of Looking: INVISIBLE LIGHT | Banana Music

“I wouldn’t know a gamma ray if I saw it”

Stan Lee (1922-2018)

BANANA MUSIC: radiation from a banana creates music

It's easy to forget that Gamma rays are a form of light. If we think of these rays at all, we think of them as nuclear radiation (which is correct) that has little impact on our everyday world. A banana is a rare source of this invisible light which is emitted in tiny – and therefore safe – quantities by the potassium in the fruit. This artwork is about making this most subtle light source perceptible.

© The School of Looking, Banana Music (detail), 2020.

Gamma rays are photons emitted by the nuclear decay of radioactive isotopes such as Potassium 40. Like X rays, they can pass through matter, but they are higher in energy and shorter in wavelength and, therefore, more penetrating and dangerous.

Gamma ray imagery, confined until relatively recently to physics labs, is now used in medicine (PET scans) and in astronomy (Fermi Gamma-ray Space Telescope studies the elusive but spectacular Gamma-ray bursts associated with the birth of black holes).

Like other forms of ionizing radiation, Gamma rays can be detected by a Geiger-Muller Counter.

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