SJH photochromic ink color change in sunlight test: colorless indoors, turns colored quickly under sunlight - used for security marks, color-change t-shirts and outdoor products.
A full written description of the demonstration, so the content is readable without playing the video.
This video demonstrates SJH photochromic ink changing colour in sunlight: colourless indoors, developing colour quickly in direct sun, and fading back reversibly indoors.
The video opens indoors with the printed sample, where the ink layer is essentially colourless and the pattern is hidden. Photochromic ink changes colour when excited by ultraviolet light, and window glass filters out most UV, so indoors the reaction is negligible - the security feature stays hidden and does not disturb the packaging design.
The sample is moved into direct sunlight and the ink layer develops colour quickly under UV excitation, bringing out the hidden pattern and text. Response speed depends on UV intensity and ink film thickness: fastest in clear direct sun, noticeably slower under cloud cover or in shade.
Returned indoors, the colour fades back to the original colourless state. This reversible cycle repeats, the basic property of photochromic materials. The video shows the complete loop - into light, colour develops, out of light, colour fades - which is useful for showing customers the approximate appearance in real use.
| Mechanism | Reversible photochromic reaction excited by ultraviolet light |
|---|---|
| Response | Depends on UV intensity and film thickness; fastest in direct sunlight |
| Verification | Take it into sunlight - no equipment required |
| Typical use | Security marks, colour-change apparel and outdoor products, creative packaging, teaching demos |
The great advantage of photochromic ink is zero-barrier verification: consumers simply take the product into sunlight and see the change, with no UV lamp needed - the best user experience for consumer-facing anti-counterfeiting. Note that it is sensitive to UV intensity: indoors, on cloudy days or behind glass the reaction weakens, so it works best as a supplementary feature rather than a sole security method, ideally combined with UV fluorescent or optically variable features.
Selection, detection, printing and ordering — answered.