Forgetting Light

I have wanted to experiment with real time visuals and photochromic pigment for a long time, and finally got my hands on some tools to experiment. There is a lot to cover, so I'll stick to some bullet points:

• This is not a normal digital screen
• The canvas is painted with white->blue photochromic pigment that has been mixed with an acrylic base
• I worked with a manufacturer in China to make me a custom RGB ILDA laser projector, but I asked them to swap the normal 435nm blue laser with a 405nm UV laser
• The white->blue pigment fades from blue to white over about 15 seconds. Some pigments from certain manufacturers fades more quickly.
• Exposure time effects the color saturation, so a long/bright blast will turn it blue for longer. However, the time needed is minimal and you can get away with flashing things
• There are lots of other pigments like orange, yellow, purple and blue that can even be combined. You can even mix in glow-in-the-dark pigment as well.
  • The ones im using are likely "T-type" photochromic pigment, but there is also P-Type which reacts differently and can actually be "erased" by other light
• Other pigment colors react differently from blue - purple lasts maybe twice or three times as long, and yellow and orange feel like they take more than 2 minutes to fade back to white. Orange also does not react to 405nm, but i suspect it needs something more like 385nm, but those diodes are expensive (and more dangerous)
• Rear projection is possible, as is very large scale projection. Rear projection does not expose as well or takes longer.
• I am using the lovely Liberation laser software for control. I am still working on other techniques for visualizing.
• UV light is incredibly dangerous, and it is unknown how I would get permits to exhibit this publically.

Other projects and artists with similar techniques:

• Kohei Nawa - laser projection on photochromic pigment encased in resin
• Robert Henke - laser projection on glow in the dark
• Alberto Novello / Jestern - audio reactive laser projection on glow in the dark surfaces
• Random International - UV LED array passing over photochromic pigment like a printer or inverse scanner
• Related topics:
  • Magic Ink tattoo ink
  • Photo-chameleon using P-type photochromic dyes that can be "erased"

Potential Future Directions:

• Modify a DLP projector to have a UV light source or source a UV projector that is used for 3D printing with resin - this would allow for high resolution images
• Get a grid of UV LED behind a photochromic canvas and create images behind the canvas - might be safer for regular viewing

Example Work:

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©Blair Neal 2020