How to Choose a Liquid Crystal Sheet Temperature Range
Liquid crystal sheets only show colour inside their own temperature range. Choose the wrong range and you'll see little or nothing: the sheet stays black, or it's already fully coloured before anyone touches it. This guide explains how the ranges work and how to choose the right one for your application.
What the temperature range actually means
As a liquid crystal sheet warms up, its colour changes in a set order: black → red → green → blue → black. Each change happens at a defined temperature:
- Red start: the first colour appears as black turns to red. This is the lower number in the range.
- Green start: usually about 1°C above red start.
- Blue start: the upper number in the range.
- Clearing point: the colour fades back to black, a few degrees above blue start.
So a 25–30°C sheet turns red at about 25°C, green at about 26°C and blue at about 30°C, then returns to black at roughly 34°C. The sheet shows colour across a slightly wider span than its name suggests. Below the range it's black; above the clearing point it's black again.
The difference between red start and blue start is called the bandwidth. A 25–30°C sheet has a 5°C bandwidth; a 35–36°C sheet has a 1°C bandwidth.
Wide or narrow bandwidth?
- Wide (5°C): covers a broader spread of temperatures. Best for seeing the overall pattern: where a surface is warmer or cooler, how heat spreads, or where a hand has been.
- Narrow (1°C): the whole rainbow happens within a single degree, so very small temperature differences show as clear colour changes. Best when you already know roughly the temperature you're working at and want fine detail around it.
The most common mistake: forgetting the starting temperature
The sheet shows the temperature of its own surface, which starts at the temperature of the room or the object it's fixed to.
- If that starting temperature is already inside the range, the sheet is coloured before anything happens, and a touch or heat source makes little visible difference.
- If it's well below the range, the sheet stays black unless the heat source is strong enough to lift it to red start.
For a touch effect, choose a range whose red start sits just above the surrounding temperature. Skin is warmer than a normal room, so a hand or fingertip lifts the sheet into its colour range and leaves a coloured print that fades as it cools.
Choosing a range: a starting point
| Range | Colour starts at about | Typical uses |
| 20–25°C | 20°C | Room-temperature and cool surfaces, airflow and cooling patterns, displays in cool rooms |
| 25–30°C | 25°C | Touch-responsive surfaces in a normal room, interactive displays, classroom demonstrations |
| 29–33°C | 29°C | Skin contact, jewellery, wearable and body-contact designs |
| 30–35°C | 30°C | Warm skin and surfaces, warm equipment, general temperature visualisation |
| 35–36°C | 35°C | Fine detail around 35°C: a narrow band for spotting small differences |
| 35–40°C | 35°C | Warm equipment, heated surfaces, warm water |
| 40–45°C | 40°C | Hotter surfaces such as electronics, pipework and heated components |
These are starting points, not guarantees. Real results depend on room temperature, the material underneath, airflow and how long heat is applied. Aim for the colour you care about, usually green, to fall at the temperature you most want to see.
Some ranges, particularly those above 35°C, are usually made to order. Please contact us to check availability.
Test before you buy full sheets
If you're not sure which range suits your application, start with our R&D Evaluation Pack: seven calibrated sheets covering 20°C to 45°C. Place each sheet on the actual surface, in the real conditions, and see which gives the colour you want. The pack includes £20 credit towards a full-size sheet.
Precision or creative sheets?
- Precision-calibrated sheets: colour changes start within about 1°C of the stated temperature. Choose these for thermal mapping, product testing, engineering, laboratory and R&D work, or anywhere the temperature reading matters. Adhesive-backed as standard; non-adhesive on request. View precision liquid crystal sheets →
- Creative sheets: for design, fashion, classroom and display work, where the effect matters more than an exact reading. Ranges are approximate. View creative liquid crystal sheets →
Getting the best results
- View straight on in good, even light. Colours shift with viewing angle and lighting.
- Cut to shape with scissors, a craft knife or a guillotine.
- Fix the sheet flat to a clean, smooth surface so it takes on that surface's temperature evenly.
- Protect fitted sheets from direct sunlight (UV) and from solvents, which damage the liquid crystal.
- Store unused sheets at 20–25°C, out of direct sunlight and away from solvents. Shelf life is about 12 months.
- Reusable: the colour change is reversible and can be repeated many times. Check the colour response now and then to make sure it hasn't changed.
Need a different range or size?
We supply individual makers, schools, designers and businesses worldwide. Other ranges, larger quantities, rolls and non-adhesive versions can be supplied to order. Contact us with your application and the temperatures you need to see, and we'll confirm suitability, lead time and minimum order.