X-Peri-Mas #3 – A rainbow on a plate

This is one you may have seen before – using Skittles to make a rainbow pattern on a plate. If you have seen this one before, why not try out X-peri-mas #1 or #2 instead?

I love this little experiment because it’s never the same twice. I also use it in public shows when I need a little time to set up something a little bit more complicated than normal because I can get young volunteers up to make the pattern and then give it a minute while the experiment works.

A satisfying box of starting materials…

What you will need:

  • Skittles
  • Water
  • Plate
  • Flat surface

It’s as simple as that. Place skittles on a plate and then pour water into the plate.

The fun comes when you think about how you might get a specific pattern – maybe you want a realistic rainbow?

Maybe you want to make a more abstract tie-dye style pattern?

Or what about something with a Christmas feeling – a star or a snowflake?

Depending on where you put the skittles you can get a variety of patterns at the end.

The supercut of skittle patterns

I’ve experimented with quite a few different ways of shepherding the colours to go where I want them and haven’t always been successful.

I attempted to use a stencil to apply a coating of a hydrophobic oil onto the plate – hoping that the water-based skittle colours would avoid it and leave a star.

Didn’t work.
I fail a lot – I thought you might appreciate seeing some of the ideas that did not work.

So what’s actually going on?

The colour on the outside of skittles is actually soluble in water. This means that is can come loose from the sweet itself and go for a little swim in the water that we have added. The warmer the water, the happier the colourful molecules are to go for that swim! This means that if you use hot water the colour dissolves faster and will make your pattern faster too! So that’s why the colours come off the sweets and go into the water instead…

…but why does it form the pattern?

Well, as the colour molecules dissolve off the sweets they like to spread out and move about in the liquid. The molecules will move in all directions but we will definitely notice if they spread out away from the sweets because areas of the water that weren’t colourful before will suddenly become colourful! If all your sweets are around the outside all the colours will run towards the centre of your dish.

When the stripe of one colour meets the stripe of the other, the colours don’t mix straight away. Imagine that there are lots of people just swimming about and splashing away in the water. If you and your friends all start in the same place then you will start to head in a similar direction. When you come close to another group of swimmers you’ll all bounce off each other and clash – to avoid these clashes you can all start to go in the same direction – away from where you started. Where there are clashes, we will see sharp lines between the colours. But if you wait long enough, the swimmers will start to find gaps between the groups and start to mix… after about half an hour we end up with the same brown mess with totally white sweets in it, no matter what you start with. It would be sad, if it wasn’t so easy to just make a new, pretty pattern!

Try it out and remember to share pictures of your creations with me on Twitter with #XPeriMas!

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