Firework in a glass

As it is nearly Bonfire night in the UK we thought was should do a firework experiment. This is totally safe, very easy and looks just like a firework without the bang and sparkle.

What you need

A tall glass and a smaller glass

Warm water


Food colouring


  • Fill a tall glass with warm water almost to the top.
  • Pour a couple ot tablespoons of oil into another glass and add a  few drops of food colouring.
  • Mix up the oil and food colouring.
  • Pour the food colouring and water mixture into the warm water and watch the fireworks.

The Science Bit

Oil and water do not mix!  Also Oil is less dense than water (meaning there is less of it in the same volume) and therefore floats on top of water in a nice layer.

The food colouring we used was water based and therefore does not mix with the oil, instead it sinks through the oil into the water below.

Since the addition of the colouring makes the food colouring heavier than the water it sinks to the bottom leaving trails (resembling fireworks) as some of the colour diffuses into the water.

We noticed that some blobs of food colouring sank to the bottom and then after a few moments shot up (resembling a more conventional firework) – Why do you think this might have happened?*

*We think this might be because an oil droplet was trapped inside a food colouring droplet and sank, but as the edges of the food colouring droplet diffused into the water suddenly the drop became lighter than the surrounding water (thanks to the less dense oil at the centre) and floated upwards quickly… 

Author: Emma Vanstone

Science Sparks, is a site dedicated to making Science fun for kids. I’d love you to follow me on my Google Profile+.

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  1. Emma,
    What a coincidence! We too enjoyed a similar experiment in bottles. We added fizz tablets that cause really firework-like reactions. Just linked it up above.

    Post a Reply
    • Oooh let us know how you get on. xx

      Post a Reply
    • oh yes, of course. I will check it out now. xx

      Post a Reply
  2. …aw, Guy Fawke’s Night! My husband is actually descended from Tresham’s who came to the US after their relatives failed involvement with the Gunpowder plot – maybe we should light a bonfire too :)

    Post a Reply
    • oooh really? How interesting. You should join in the celebrations. xx

      Post a Reply
  3. This is wonderful!!! I cannot wait to do this with my little one. Your site is amazing – Thank You!!!

    Post a Reply
    • I’m so glad you like is, thank you. xx

      Post a Reply
  4. This site is great! My son loves science, and I am always looking for ways to foster that! Pinned, and your newest GFC follower!

    Post a Reply
    • I’m so glad you like us, thank you. xx

      Post a Reply
  5. Wow! Looks absolutely fabulous! Don’t you just LOVE SCIENCE :-)

    Thank you for sharing on Kids Get Crafty!!


    Post a Reply
  6. looks great, love all your experiments and you’re filling such an important little spot in our party that was empty until you came along! thanks so much for stopping by regularly to share on Craft Schooling Sunday, i really appreciate it!

    Post a Reply
    • So glad you liked it! x

      Post a Reply


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