Light Party does Science! (Part 2) Experiments

We can have a lot of fun with all types of glow-in-the-dark sciency stuff, while thinking about how God is the source of all light and we can shine his light out.

Here are lots of ideas for a light party with a science twist, such as luminous letters, fluorescent food, and glow stick (naturally) games.

glowing oil and water experiment for kidsOil and Glow-water

Do this activity under normal and UV light

You will need:

  • Fluorescent paint (click) *
  • Cooking oil – olive oil and canola (rapeseed) oil if you want it to fluoresce, or any other cooking oil or baby oil
  • Screw-top bottles (water bottles are ideal)
  • Mustard (optional, Dijon is best)

Half-fill a small bottle with cooking oil, then fill the rest with water. Watch the liquids swirl and separate into layers. Which is on top? Why is that?

Add a squirt of fluorescent paint or dye. Does it mix with the oil or the water? Why is that?

Screw the top on tightly and give your bottle a good shake. What can you see? Where is the dye now?

What does it look like? Can you make the layers mix? Do they stay mixed?

(optional) Add a little mustard to the bottle and shake it again. What is different this time? Can you explain why?

Alternatively, fill a glass casserole dish with baby oil and drip diluted paint in. Swirl the coloured water and make fabulous patterns.

The Science Bit

Mustard is an emulsifier, a chemical that has a water-loving end and an oil-loving end. This helps oil and water to mix. A mixture of oil and water is called an emulsion. Detergents such as soap and shampoo do the same thing, helping water to stick to oily marks and wash them away.

Talk About

Some people think that faith and science don’t mix, like the oil and water. What do you think?

(With thanks to Jeweled Rose)


fluorescent dyeGlowing Fountain

Do this activity under UV light

You will need:

Put a small amount of luminous paint or dye in the hot water and fill one glass, right up to the rim. Place a CD on top, slightly off-centre.

Fill the other glass right up to the rim with cold water, and cover with a CD, slightly off-centre. Now here’s the possibly messy bit! Holding the CD in place, quickly put the cold water glass upside-down on top of the hot water glass. Make sure that the holes do not line up.

Now turn off the lights and turn on the UV. The bottom glass should be glowing and the top glass not. Push the CDs together so that the holes overlap.

What can you see? Why is this happening? Would it work with the glasses the other way up? Why is that?

The Science Bit

Water expands when it is warm and becomes less dense, so a spoonful of hot water weighs less than a spoonful of cold water. This is how hot-air balloons work. The hot air inside the balloon is less dense than the air outside and it rises. Hot-air balloons work best when the air outside them is cold and dense.

Things float because they are less dense than whatever they are floating in. Oil is less dense than the water, ice cubes are less dense than fruit juice, and ducks are less dense than ponds.

When we line up the holes in the CDs, we let the hot and cold waters mix. The hot water is less dense and rises up, like a fountain. The cold water flows down to replace it.

If the glasses were the other way up, the hot water would already be at the top, so nothing would happen.

If your fountain does not work well, it might be because the fluorescent paint or dye increases the density of the hot water too much. You could dye the cold water instead and have a glowing fountain.


Tonic_water_uvSecret Pictures

Do this activity in normal and UV light

Tonic water fluoresces because it contains quinine (originally it was an anti-malaria medicine, hence ‘tonic’).

We can use that for sending secret messages that can only be read under UV light.

You will need:

  • Tonic Water
  • Paper
  • Paint brushes
  • Watercolour paints

Make up some watercolour paint with tonic water, and the same colours with normal water.

Paint your secret message or secret picture using the tonic water paints. Then continue painting around your secret with the normal paints.

See if you can disguise your picture or message. For example, you could paint lots of other letters to hide a written message, or a sun could be hidden in a flower.

Now – can others read your secret message? Turn on the UV and see it revealed!

Talk About

God is invisible. How can we know about him?

Check out John 1:18. Perhaps you could write this verse in invisible writing.



Do this activity under UV light or in the dark

Who doesn’t love slime? Make it even better by using tonic water to get glow-slime!

You will need:

Children can make their own slime, or you can make it in advance. Although this might seem a messy activity, the slime dries to a dry powder which brushes up cleanly.

Place the cornflour in a bowl and gradually add tonic water until the mixture is just liquid. You should be able to move your spoon through it smoothly without it catching. The perfect mixture will be solid enough that you can punch it and it feels hard, but liquid enough that you can stir it slowly.

Can you roll a ball of slime between your palms? Can you squeeze a handful of it?

Pour some into tray and write messages or draw pictures in it. Can you build a tower?


Light Party does Science!


* Clickable links

The clickable links will take you to suggested items on Amazon via an affiliate link. If you purchase any items after following an affiliate Amazon will make a small donation to support this ministry. So feel free to splash out on that diamond-studded Porsche. No personal data is passed in either direction, and the price you pay is exactly the same.

Please note: The suggested items are necessarily exactly the same as the ones I use. So while I have linked to ones that are as close as possible to the ones tested so I cannot vouch for their suitability.

4 thoughts on “Light Party does Science! (Part 2) Experiments

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