How to Spray Hydrochromic Ink
SFXC® Hydrochromic Sprayable Ink, also called water-reactive or water-activated ink (or hydrochromic paint), is white when dry and turns see-through when wet, revealing whatever is underneath. When it dries, the white returns. This guide explains how to spray it for the best result.
If you're printing rather than spraying, see our guide How to Screen Print Hydrochromic Ink.
Specifications at a glance
| Effect | Reversible: white when dry, transparent when wet |
| Ink system | Water-based, ready to spray |
| Application | Standard spray equipment or airbrush |
| Coats | Two thin, even coats |
| Drying | Air dry, or warm air kept moving |
| Curing | 130°C for about 3 minutes; 130–150°C for 3–5 minutes for best adhesion and water resistance |
| Storage | Not above 25°C; do not freeze |
| Shelf life | 6 months |
| Sizes | 100 ml, 1 litre and 5 litre |
What you'll need
- SFXC Hydrochromic Sprayable Ink
- A spray gun or airbrush (standard spray equipment is fine)
- Your design or colours underneath, already dry
- Masking tape for any areas you want to keep clear
- A test piece of the same material
- A hairdryer (optional, for drying)
1. Choose and prepare your surface
The sprayable ink suits wood, heavyweight tight-weave fabric, stone and board. Test any other material first.
- Use a smooth surface. In ridges and grooves the ink collects too thickly and won't turn clear.
- Absorbent surfaces must be primed with a suitable water-based primer before you spray, otherwise they soak up the ink unevenly. Every material behaves differently, so test on a primed sample first.
- The surface must be clean and dry.
2. Plan the colours underneath
The ink is white, so it can hide light and mid colours but not strong dark ones.
- Avoid black, dark blue, dark green and red. They will show through the white.
- Use lighter versions instead, such as grey, light blue, light green and pink.
- The white layer softens colours slightly when they're revealed, so don't go too pale either.
- Let the colours underneath dry fully before you spray.
3. Prepare the ink
Contents may settle in transit. Shake the bottle well before use, or stir larger containers thoroughly. Don't mix it with other inks.
4. Spray
- Follow your spray equipment maker's guidance and test on a sample first.
- Apply two thin, even coats. Let the first coat dry before applying the second.
- Two coats are best. A third coat can be too heavy: the ink may stay white when wet instead of turning clear.
- Don't apply with a brush or roller. Spraying is the recommended method because brushes and rollers leave uneven, heavy deposits that stop the coating turning clear when wet.
- Spray in a well-ventilated area and avoid breathing the spray mist. Read the Safety Data Sheet before use.
5. Dry and set
The ink air dries. To speed it up you can use a hairdryer: keep it moving and waft the warm air over the surface, and never let it scorch or burn the coating.
Where your material can take the heat, baking gives the toughest finish and the best water resistance: about 130°C for around 3 minutes, or 130–150°C for 3 to 5 minutes. Not every material tolerates this heat, so test yours first.
Please note: drying with a hairdryer is not the same as baking. A hairdryer dries the coating but doesn't set it as fully, so items that can't be baked should be treated as more delicate, especially outdoors.
6. Clean up
Clean your spray equipment with water straight after use. Don't let ink dry in the gun or nozzle.
7. Using it
- Reveal it with clean water. Other liquids can leave marks that don't clear.
- The ink changes as soon as it's wet. How quickly it turns white again depends on how quickly it dries: faster on a warm day, slower on a cold one.
- Store unused ink at 25°C or below and don't let it freeze. Shelf life is 6 months.
Outdoor and large projects
Hydrochromic ink has been used to create interactive murals and installations where water reveals hidden artwork, including projects with fountains and water features.
For outdoor projects, think carefully about weather, surface preparation, adhesion and how long the installation needs to last. Rain may reveal the artwork unexpectedly, and long-term outdoor durability should not be assumed.
If your installation is meant to stay outdoors, please contact us before you start. We can talk through what you need, advise on testing, and discuss a mix made for your project.
Troubleshooting
- It doesn't turn clear when wet: the coat is too heavy, or there are too many coats.
- Dark colours show through: the colours underneath are too strong. Lighten them.
- Patchy finish: the coats were uneven, or the ink collected in grooves.
- Marks stay after it dries: something on the surface (for example, a printed or solvent-based finish) may be interfering, or a liquid other than water was used. Before re-coating, prime a test piece of the same surface and check it on that first.
- Coating rubs or flakes off: the surface wasn't primed or clean, or the coating wasn't fully dried and set.
Sizes, bulk and custom mixes
The sprayable ink comes in 100 ml, 1 litre and 5 litre sizes. Start with 100 ml to test on your material. For larger projects, bulk quantities or a mix made for your project, contact us.
Before use: please read the Technical Data Sheet (TDS) and Safety Data Sheet (SDS), and always test on your own material first.
See TDS information (Revision 1, October 2026) | See SDS information (Version 1.0.0, October 2026)
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