Fantastic UV photochromic powder

These amazing pigment powders change from white to a colour when exposed to UV or near-UV light, and then gradually reset to white again afterwards. Even a small amount of pigment in resin has a very distinct effect.
The packaging comes with a strong set of warnings including risks of flammable dust, inhalation risks, contact sensitisation and eye damage. Further investigation of MSDS data sheets suggest these may be aimed at high exposure industrial use, but there's no harm taking precautions.
The powder consists of the photochromic chemicals microencapsulated for protection when used in things like inks. It's ultra fine, and quite hard to scoop out a controlled portion.
Only a small amount is needed in resin to give a vivid colour change, as shown in the video.
In the UK I got this from an eBay seller called perfectpearlsandpigments (not a sponsor) who seem to supply exotic pearlescent glitter additives to the specialist paint industry.
www.ebay.co.uk...
A quick search shows that the pigment is also available from the usual online suppliers, including unusual photochromic glitter particles for nail-art.
The effect is very impressive. A solid change of colour when exposed to wavelengths in the near UV to UVA region (400nm or less). A blue LED did not trigger the effect, but a near-UV one did.
The change is also vivid in sunlight which is roughly 3% UVA.
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