rainbow_5If your kid loves colour, then this is a beautiful party theme. You can go wild decorating your house in bold, beautiful rainbow colours, which can easily be found in party stores, along with colourful party bags and favors. Although the theme can open itself up to lots of ideas, we want to make it a fabulous science party, so my ideas are going to focus on cool science demos and experiments rather than anything else.

Before we get the science ideas rolling, I suggest you make a fabulous rainbow cake. It may seem daunting but I’ve found a great video that can walk you through it!

Rainbow Cake

You can find loads of other rainbow coloured party food videos online.

Wow the kids!

Usually you have to wait for a rainy day to see a rainbow. Well, now you don’t. Why not make a rainbow at the party, which will highlight the principles of how a rainbow is formed.

Rainbows appear when white light, such as the light from the sun, bends as it passes through a medium. White light is made up of different colours (all the colours of the rainbow) and these all travel at different speeds through the medium. Their differing speeds results in them bending (refracting) at different angles, separating the colours out. It is this splitting if the white light that creates the rainbow.

This can be explained with a really simple demo, such as the one below.

Another way to show how white light is made from the colours of the rainbow is to get the kids to create their own rainbow spinner.

Now, where else do you find rainbows being formed? Ask the kids!

Rainbows are cool to make indoors and there are several ways. Here are a few the kids can try:

Test tube rainbow

This is more like a density rainbow, as the colours of the rainbow sort by their density rather than the sequence they appear in the rainbow. However, there is lots of science which will get the kids thinking.

Milky rainbow

This definitely gives the kids the “wow” moment when they see what happens to the food colouring when they add a bit of detergent to the milk. Also, use 2% or 1% milk – not skimmed as we need the fat!

You may decide to make this more of an experiment where the kids will test different types of milk and cream.You can find out more science and test ideas here.


Get crafty!

There are lots of great science craft projects we can do with this theme. Here are a few:

Tie-Dye T-shirt

Have artistic fun while learning about chemistry. A fun, yet mess free way to create your own tie-dye shirt is to use sharpie pens. Here is a step-by-step set of instructions in this video.

So what is the science? The permanent ink in the sharpie pen is not soluble in water because the ink is hydrophobic (water hating). However, when exposed to rubbing alcohol the molecules in the permanent ink are able to dissolve (they are soluble) and thus can be carried with the alcohol as it spreads through the shirt.


This is a great way for kids to marvel at the light and really appreciate the beauty of colours. There are quite a few bits and pieces to this science craft project so it may be best for you to cut to size some of the things beforehand.

So what is the science? When travelling in an empty space, light travels straight. However, when it hits an object it changes its direction. Some of the shiny surfaces like the plastic, which is used in this demo, or a mirror, reflect the light back (like a ball bouncing off a wall). The plastic tube inside this kaleidoscope reflects the beads, gems, and all the beautiful shiny objects we put into our tube. As the reflections travel back they bounce back and forth from side to side thus creating several identical images. By turning the kaleidoscope, you move the pieces, creating different designs.

Rainbow Playdough

I think this is a good one to put in the party bag along with instructions on how to make it. When home the kids can recreate the playdough with their parents while learning about the science.

What you need:

3 cups of flour

1 1/2 cups of salt

2 tbsp cream of tarter

3 tbsp veg oil

3 cups of water – add food colouring (you can make several batches of playdough using different food colouring each time)

Instructions: Mix all the ingredients in a large pot. Cook on a low heat, stirring continuously. When the dough forms a large ball, remove it from the heat, cool and knead. You can then keep it in an airtight container or ziplock bag.

Science to think about: Cooking is just like chemistry – different ingredients come together, a reaction takes place and we’re left with something new. So what is happening in this case? Flour contains protein and by adding the water the protein in the flour swells up like a sponge, becoming tough and elastic. This new material is gluten. When we add salt to this dough, it helps to slow down the breakdown of the protein, so we can easily knead and play with the dough. Why not try adding different amounts of salt to the dough and see what happens. If you don’t add enough the dough stays sticky and rubbery.


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