Heat Sensitive Phone Cover





Introduction: Heat Sensitive Phone Cover


So over the past few weeks i have been involved with a project called A Shedload of Science in partnership with Glasgow Science festival (links to their websites below) and its given me the opportunity to work with some materials i haven't worked with before. One of these is Thermochromic pigment and we will be using this today to make a colour changing heat sensitive phone cover.

Now before you think "Thermochromic pigment? sounds expensive and hard to come by." Its pretty affordable and available at online retailers. We used Maplin which was £2.99 + P&P for 5ml which you mix in with paint so you end up with more.



Step 1: Materials and Tools


Thermochromic pigment.

I'm using magenta here another thing to note is because we are mixing it with acrylic the end colour will be lighter but i will go into that more in the next step

Acrylic paint.

I'm using white here as the colour change is more dramatic.

hard phone case.

I'm using one bout from the Pound shop so it doesn't need to be expensive.

Clear Lacquer.

I'm using spray on but a thin layer of any clear coat varnish would do the trick



Sandpaper. fine coarseness

Small container to mix the paint and pigment in

Step 2: Mixing Your Pigment

As mentioned before because you are mixing it with acrylic paint you are going to get some colour change. as i am using white with magenta its lightened down to a more pinky colour pink. Take this into consideration when mixing your paint/pigment as you can get some nice colour changes, For example mixing red pigment with yellow paint will give you an orange paint that turns yellow under heat or blue pigment with red paint will give you a purple paint that turns red.

There doesn't seem to be any information about proper ratios to use when mixing pigment and paint but i have been using a rough ratio of at least 2 parts pigment to 1 part paint. (EDIT: I have since found out the recommended ration is 4 to 1)

I have dabbled in using the pigment "straight" but it doesn't seem to work as well without the acrylic as it goes a grey in colour and when you can only get it in 5ml shots i could see it becoming quite expensive

To mix it I put it in a small container and mixed with the brush.

Step 3: Prep the Case

To prep the case i gave it a rub over with the sand paper to get rid of the glossy feel and help the paint stick. once i had gave the outside a sanding i gave it a rinse and dried it off.

Step 4: Painting Your Case

Yup, its that simple.

I ended up giving it 3 coats letting it dry between coats*, mainly as the pattern kept showing through (once the phone is in it it doeskin show through as much but as i use my phone to take the photos you can see my conundrum). the photo above is after 1 coat

Once dry I gave it 2 quick coats with the lacquer waiting for it to dry between coats*.

*You can speed this up with a hair dryer but don't freak out when the colour changes, it's supposed to do that remember ;)

Step 5: Done!

And there you have it, a heat sensitive phone case.

There is a video below of it under the hair dryer.

I only did it one colour but you can do different colours, patterns, pictures or just where ever your imagination takes you.




  • Science of Cooking

    Science of Cooking
  • Microcontroller Contest

    Microcontroller Contest
  • Spotless Contest

    Spotless Contest

We have a be nice policy.
Please be positive and constructive.



Can you mix the pigment with a glow in the dark pigment?


So If i used a Imaged case and used a light color say hot pink after the process is completed and i apply heat would the said image be visible through the coloring?

just a random thought

The pigment isn't transparent so it would cover any image underneath it. you could do it by matching the mixed pigment with the same colour of paint and painting a design on top of the colour change paint. this way when its at room temp both paints would match but when heated the non colour change paint would remain the same.

does that make sense?

thanks that is extremely helpful and saved me a botched case

When you but the pigment is it a dry powder? I'm confused.

My friend bought me the pigment for my birthday and it was a super fine powder. I believe that's how it comes in most cases

I had completely missed gwyniesimpson's comment, thanks for answering it :)

Sorry, i missed this comment, dont know how. as XxAlziexX below says it seems to be more readily available in America as a powder and as a liquid in the UK. I have used both now and the results are the same.

Does this work on clear hard cases?

Unfortunately the pigment turns a grey colour when its warm when mixed with a clear substance (like nail polish) so you never have a transparent base coat.

Brilliant to see an Instructable from Glasgow. Mon Glasgow. Keep up the great work, and I look forward to seeing further projects in the future.