Introduction: Heat Sensitive Phone Cover

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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!

Picture of 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.



Eric C.C (author)2016-01-21

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

Barry Neeson (author)Eric C.C2016-01-25

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?

Eric C.C (author)Barry Neeson2016-01-25

thanks that is extremely helpful and saved me a botched case

gwyniesimpson (author)2015-10-17

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

XxAlziexX (author)gwyniesimpson 2015-11-27

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

Barry Neeson (author)XxAlziexX2015-11-28

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.

Gavinbullock (author)2015-09-25

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.

smac74 (author)2015-09-22

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.

Barry Neeson (author)smac742015-09-28

Thanks :)

isrigopal (author)2015-09-20

This is really cool. I want to make a thermochromic device i can use to place in my mouth or against my jaw to test whether my root canals are rotten and emitting heat to help me decide whether to have them removed or not. Do you think these materials could do the job? Is the pigment sensitive enough? Thank you.

Barry Neeson (author)isrigopal2015-09-21


Given that i am not an expert in any way about thermochromic pigment (i'm just starting to experiment my self) or in dentistry I would recommend seeking out someone in either of those fields (the dentist would probably be the easier to find)

what i would say is I don't think it would work given as the paint reacts to body heat and i would imagine that the heat from your mouth would make it change regardless.

All the best and i hope your root canals are fine and you dont require any work

isrigopal (author)Barry Neeson2015-09-21

Thank you, sir. Very nice reply. Hope you keep enjoying your experiments and instructables.

paddyding (author)2015-09-19

Wow I didnt know that thermochromic paint is that affordable. Good work!

Barry Neeson (author)paddyding2015-09-20

Thank you :)

UK Ninja96 (author)2015-09-18

What if you mixed the pigment with a clear coat?
Awesome project btw I really want to try it on somthing I don't know what yet

Barry Neeson (author)UK Ninja962015-09-20

Thanks for the comment. I'Im actually going to do some more experimentation with the pigments when i get the chance

SidA2 (author)2015-09-17

what if you swirl dip the case in paint so its a color changing swirl?

Also, can you paint acrylic paint first and then paint on heat paint so that the colors don't mix? That way you can go from blue to red instead of purple to red.

Barry Neeson made it! (author)SidA22015-09-18

I pretty sure that would work but you would probably want to mix your two pigment/paint colours separately and them mix those two mixtures into the swirl. I have attached a ping pong ball i did using a combo of light blue to white, pink to white and purple to red so you can see the use of multiple colours :)

From what I can gather the pigment needs to be mixed with the paint. as i mentioned i tried using the pigment by itself and when heated it turned to a grey colour.

Hope that helps :)

thatzhitesh (author)2015-09-17

The project is awesome. But i actually i did not understand how and when to use lacquer. Did u use it while mixing paint and pigment or did u use it as coating after final coat of colour. Pls guide me. Thnks for sharing.

Barry Neeson (author)thatzhitesh2015-09-18

Thank you.

I put the lacquer after the final coat of colour :)

ThatSteeve (author)2015-09-17

is it wrong that this instructable excites me? I didn't know thermographic pigment was readily available. Well if it is wrong I don't want to be right! ;)

Thanks for sharing!

Barry Neeson (author)ThatSteeve2015-09-18

It's not wrong at a all and thanks for commenting. looking forward to see what you come up with :)

srilyk (author)2015-09-17

I suspect if you used some gray/white primer before your paint you'd get away with less coats :)

Barry Neeson (author)srilyk2015-09-18

I imagine you would be right. i was eager to give this a go and probably rushed into it but im keen to experiment more :)

Dr The BoB (author)2015-09-17

Wow, there is so much potential for awesome here... thank you for the inspiration. :)

Barry Neeson (author)Dr The BoB2015-09-18

Thank you for commenting and i cant wait to see what you come up with :)

Linkin_J_Knex (author)2015-09-16

Great idea! :D By heat sensitive what do you mean?

It changes colour when heat is applied to it, in this case its pink and when heat is applied (like your fingers) it changes to white

That's so cool :D I will favourite it!

Thank you

KyleTheCreator (author)2015-09-16

Great instructable! I can already see many uses for this technique! If the base coat paint that you used to mix with the thermochromic pigment was clear, like a epoxy or resin, would the color change from pink to clear?

Im not sure, its certainly worth experimenting with. my only concern is when using the pigment straight it turns grey rather than clear.

Will give it a try and let you know

kdinis (author)2015-09-17

your a left handed

Barry Neeson (author)kdinis2015-09-17

Im right handed but its easier for me to hold the camera and take the photo with my right :)

About This Instructable




Bio: I graduated from Cardonald College with an Advanced Diploma in Graphic Design in 1999. He has worked as a Tattoo Artist, Community Artist, and Freelance ... More »
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