Thermal Colour Changing Mugs - Made With Sugru (Silicone Glue)

We've all done it - made a tea of coffee, got into our work, and it's gone cold! Well, this Instructable shows you how to make a colour-changing pigment from Silicone Glue, (Sugru) and Colour Changing Pigment, that will change colour before your cuppa gets too cold! Thanks for voting if you liked it =)

Why make mugs colour-changing?

= Do you need more science associated with your coffee-break?

= Do you want to make a cool present for your material-scientist buddy?

= Do you want to enhance and blend the thermo-visual boundaries of your life?

This Instructable will show you how to make a mug (base) which changes colour when when you get it hot.

Chemicals Used:

Sugru is a Mouldable Glue, which sets in 24 hours to a waterproof, thermally insulating, durable rubber adhesive.

ThermoChromatic Pigment in powder form can be easily kneaded into Sugru.

You Will Also Need:

Mug / Glass Mug; 1x-2x 5g Packs of Sugru; Scalpel, Cocktail Sticks / Wooden Coffee Stirrer; Scrap Sheet of Plastic; Small Cup of Water (with 1-2 drops of liquid soap in); Gloves if you have them.

Beyond ThermoChromatics...Make Your Own Ceramics:

The glass shown here, has some rather lovely refraction of the colours (the rim glows with the colours of the base). However, if buying a mug is simply too easy for you I've also written an even more elaborate and ambitious exploration of these methods and how to make your own ceramics mugs, here.

Notes:

Disclosure: I used to work as Head or R&D, but this is not intended as a plug to sell product, I just think it's pretty cool stuff to use. Similarly, the views, comments and ideas here are my own and do not necessarily reflect those of the company, etc.... and besides, it's my weekend. TDS available here, if you are wanting to get into more details.

Step 1: Knead Sugru & Pigment Together

I found that you only need about 0.1g of TC Pigment to 5g of Sugru.
If you don't have scale accurate to this, it looks like about the amount shown here at the start (around 1/2 a teaspoon).
Knead it together for about 1-2mins vigorously. Note - when you think it looks 'mixed', know that the black colour is actually just going 'transparent' with the heat of your fingers, so touch the blob on a cold surface for a few seconds to revert the colour - if it's streaky, keep kneading.

I used the gloves to handle the pigment, for cleanliness, but it is non-toxic.
I also put some scrap paper down, as this stuff goes everywhere if you are not careful! (Have a damp paper towel to hand).
I've used Black TC Pigment here, which turns 'transparent' over 33C, so if you mix it with Red it will look dark red-brown when cold, and revert back to bright red when warm/hot. Other colours are available.

Step 2: Begin Making the Base

Roll into a ball. This not only presses out air-bubbles, but also makes a sphere - which will spread out more evenly.
Press out with your fingers, turning the mug as you go to keep it even.

Step 3: 'Buff-Out' the Base

Taking some scrap plastic sheet, which is clean and free from dirt and scratches, add a small puddle of lightly soapy water on the surface.
Push the cup down as evenly as possible. 'Buff' the cup on the plastic - make circling motions and keeping an even pressure. Turn the mug / change your grip systematically to give and even pressure.
Keep lifting up to check how even the base is getting.
Stop when you have a little excess squished over the edge of the base, all around the base.

Step 4: Trim Excess Sugru & Tidy Up

Using a scalpel, hold the blade firmly against the side of the cup, turn the cup as you cut (don't turn your hand, as the angle is harder to maintain).
Use a cocktail stick to scrape off any small debris of the cutting.
To smooth out this further, you can dip your finger in the water and rub it smooth. (More Tips at Sugru).
You can just leave it to dry now (~24 hours).

That's it if you are happy with it...or...to do more cool stuff, read on...

Step 5: Optional: Patterns & Double-Colouring

Before the Sugru cures, use a spudger, coffee stirrer or stick to make patterns, pressing about 1-2mm deep.
Give a gentle 'buff' again on the plastic, to just level it again - taking care not to crush the pattern.
Allow to dry fully for 24hours of more.

One could argue 'who's going to see this pattern?', which is true, but sometimes there's just enjoyment in knowing something is there...or you can write personal inscriptions if it's a gift, or messages to the person who sits opposite to you.

Step 6: Back-Filling the Contrasting Second Colour

Ensure the Sugru is thoroughly dry first. Test with a fingernail in a discrete place - it should leave no mark.
I mixed a 'normal' blend of Sugru (no TC pigment).
Taking a lolly-pop stick (or tongue-depressor if you have it), I worked the second colour in, working it from different directions. (try to do this in less than 15mins, else the Sugru will get hard to work with).
Scrape the excess Sugru off to reveal the pattern below.
Allow to dry again - probably overnight will do, as there is less to dry now.

Step 7: Test It!

Pour water in to see it change colour!

Note - Sugru is not 'food safe' or FDA approved, so don't put it inside your mug. Sometimes in cooler rooms Sugru can still smell a bit, well, 'Sugruy' - but it fades over a day or two.

Step 8: Other Ideas for ThermoChromatic Sugru

Work in Progress:

Indicators on Kettle for water level / water still being hot (i.e. don't re-boil!)
Indicator on top of 3D Printer to show when it's cooled down.
...Please add any ideas to comments below, thanks!

Please check out the other Instructable for advanced techniques, here, and if you are interested in other projects I do (e.g. £10 Space Pods for Superman, Off-Grid Power Generation, Solder Buddies), check out my website, Design Modelling for more projects.

Thanks for reading, please vote if you liked it, and do post any cool thing you do with this,

Cheers,

Jude