How to Use Photochromic Pigment Powder
Illustration of the photochromic effect
Photochromic pigment changes colour with ultraviolet (UV) light. Indoors it is pale; in sunlight or under a UV lamp its colour develops, and when the UV light is removed it returns to its original state. The change is reversible, so it can be repeated again and again. This guide covers how to use SFXC® photochromic pigment powder in inks, coatings and plastics.
1. How it works and the colours
The photochromic dye is very sensitive to its surroundings, so it is sealed inside tiny resin microcapsules, a few micrometres across, for protection and stability. The powder is pale indoors and develops its colour in UV light:
| Colour in UV light | Appearance indoors |
| Cobalt Blue | Slight green |
| Magenta | Slight red |
| Canary Yellow | White |
| Orange | Slight orange |
| Violet | Slight violet |
Specifications at a glance
| Effect | Reversible: colour develops in sunlight or UV light |
| Form | Microcapsule powder, odourless |
| Mean particle size | 4–7 µm |
| Moisture | Below 1% |
| Heat limit | Below 180°C, as briefly as possible; avoid prolonged exposure above 75°C |
| Light fastness | Grade 1 |
| Storage | Room temperature, dry, away from sunlight |
| Shelf life | 36 months |
2. What you can use it for
Photochromic pigment is used in printing (screen, gravure and flexographic), coatings and plastic injection moulding, on ceramic, metal, glass and textile substrates. Typical finished products include garments, shoes, accessories, stationery, household goods and security cards.
Illustration of the photochromic effect
3. Making a photochromic ink or coating
The powder needs a binder to make an ink or coating. Adjust the viscosity before use. A guideline formulation for screen printing ink:
| Material | Amount | Purpose |
| Acrylic, urethane or PVC resin | 70–75% | Controls adhesion |
| Photochromic pigment powder | 25–30% | Controls colour strength |
| Solvent (for example xylene, toluene or cyclohexanone) | Small amount | Adjusts viscosity |
Choose your solvent from the resistance chart below: the microcapsules are damaged by polar solvents such as methanol and acetone.
Results depend on the binder, substrate and process, so test on your own materials first.
4. Using it in plastics
Recommended for PE, PP, PS, PVC and PU.
- Use 20–30% in a masterbatch, giving 2–3% in the final product.
- Keep processing temperatures below 180°C and the time at temperature as short as possible.
5. Heat
- Keep processing temperatures below 180°C, and exposure as short as possible. Higher temperatures reduce colour strength and the colour-change effect.
- Avoid prolonged exposure above 75°C. The photochromic components may break down above 80°C.
6. Solvent resistance
Resistance of the pigment to common solvents (A = best, E = poorest):
| Solvent | Resistance | Solvent | Resistance |
| Xylene | A | Ethanol | D |
| Toluene | A | Dimethylformamide (DMF) | D |
| Cyclohexanone | A | Methanol | E |
| Glycols (EG, PG, PEG, PPG) | A | Butanediol | E |
| Butyl acetate | B | Acetone | E |
| Isopropyl alcohol (IPA) | C | Dichloromethane | E |
| Isobutyl alcohol (IBA) | C | Ethyl acetate | C |
| Methyl ethyl ketone (MEK) | C | Propyl acetate | C |
| Ethanolamine | C |
This chart is a guide only. Always check compatibility in your own application before commercial use.
What photochromic pigment can't do
- Last indefinitely in the sun. Light fastness is grade 1: long exposure to sunlight can considerably reduce the colour-change effect over time.
- Survive polar solvents. Methanol, acetone, butanediol and dichloromethane damage the microcapsules.
- Take high heat. See section 5.
- Skin, food, cosmetics or toys. It isn't intended for cosmetics, products applied to the skin, food contact materials or children's toys.
Troubleshooting
- Weak or no colour change: check the UV source first. Indoor lighting and light through windows contain little UV, so test outdoors in daylight or under a UV lamp. If it's still weak, too much heat in processing, a polar solvent or too little pigment may be the cause (see sections 3–6).
- The effect has faded over time: long UV exposure, acid or humidity. Keep finished items out of constant strong sunlight where possible.
- Poor adhesion: the resin may not suit the substrate. Test on the exact material.
Storage and shelf life
- Store at room temperature in a dry place, away from sunlight, with the container closed.
- Shelf life is 36 months.
- The colour change can weaken after long exposure to UV light, acid or humidity.
Handling
The powder is classified as harmful if swallowed and as a skin and eye irritant. Wear gloves and eye protection, avoid breathing the dust, don't eat, drink or smoke while using it, and wash your hands after handling. See the Safety Data Sheet for full details.
Moving from testing to production
We supply makers, printers, schools and businesses worldwide. Start with the 4-colour trial pack or a small size to test in your own binder or plastic. Larger quantities are available on request: contact us with your application and quantities and we'll confirm suitability and lead time.
Before use: please read the Technical Data Sheet (TDS) and Safety Data Sheet (SDS), and always test on your own material before production.
See TDS information (Revision 1, October 2026) | See SDS information (Version 1.0.0, October 2026)