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Can water layer on water? A stunning little experiment!

My daughter had to do a science project for school. She came up with the idea to show something amazing, that water can actually float on water. To make this visible she decided to use food coloring to give each water layer a different color.

There is, however, a little secret to the experiment. The water-layers have to have different densities; or they simply mix.

The experiment

water layers without color

Give fresh water into the left cup – and salty water into the right cup.

water layers with color

Add orange food coloring to the fresh water and blue food coloring to the salty water

layering process

Slowly add fresh water to salty water – AND LATER salty water to fresh water

waterlayers final

Left: salty water added to fresh water – the water mixed

Right: fresh water added to salty water – the water layered

Observation & Conclusion

  • The orange fresh water layers on the blue salty water.
  • The blue salty water does not layer on the orange fresh water.
  • Pouring slowly was important.


  • Water can layer on water if the layers have different densities.
  • Salt makes the density higher.
  • Only lower densities (fresh water) float on higher densities (salty water) – not the opposite.

And finally, my daughter’s poster, the way she presented it in school. Mum being very proud of the little scientist to be 😉

Tamara with science project

Thank to Tamara & Raha International School Abu Dhabi

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Hi I'm Ilka, a self-development writer and lovable scientist with a knowledgeable expertise in brain science. I help people realize the power our behavior has on our brain - and the other way around.

Eleni - February 2, 2014

That’s a cool experiment! Might try that one with my little cousins 🙂

Erratica101 - February 2, 2014

fun little experiment 🙂

Dylan Hearn - February 2, 2014

What a great experiment. I only heard of the phenomenon recently in a documentary. Divers were exploring fresh water caves in Florida (I believe), tracking the underground river to the sea. When the two waters met, the fresh water floated on the salt water, causing a mirror-like barrier between the two similar to looking at water’s surface. There were some stunning footage of divers appearing to float above the water’s surface when in fact they were swimming in the freshwater layer.

    simplyilka - February 2, 2014

    Wow! That sounds absolutely amazing. So it happened in the big ocean what we did in a little cup. Love it!

navigator1965 - February 2, 2014

A delightful application of the scientific method.

Marko - February 2, 2014

Hello! I wish you a happy and successful new week.

Denise - February 2, 2014

That’s brilliant! So simple, clear and striking.

Miss Lou - February 3, 2014

Very cool! #SmartCookie 🙂

Sherri - February 4, 2014

What a fantastic science experiment Ilka! You can be very proud of your smart scientist daughter indeed 🙂
Oh this did take me back to the days when my children took part in their school’s science fairs and had to do the presentations just the same as you show here with your daughter! I wish I could remember what they did their’s on now though! 🙂

TBM - February 12, 2014

I wish I knew this one when I worked at a day school. My kids would have loved it.

    simplyilka - February 15, 2014

    Oh! I am sure they would have. It is really easy to copy. Should you ever write a book about someone working in a day school, feel free to have her use this experiment 😉

Harleena Singh (@harleenas) - February 15, 2014

Hi Ilka,

This is wonderful indeed 🙂

I honestly didn’t know about the water densities, and I think you surely have a very smart daughter who is bound to become an awesome scientist if she chooses to be one – you must be SO proud of her 🙂

Thanks for sharing. Have a nice weekend 🙂

    simplyilka - February 15, 2014

    Thank you so much for your kind words Harleena 🙂
    And thank you for visiting my blog. I am a big fan of your blog and your lovely and positive attitude.
    And yes, I am proud of my little girl.
    Enjoy your weekend as well 🙂

Tamara - February 21, 2014

This was a really fun experiment mom I was happy to present it at school and my teacher was really proud of me

Sent from my iPad


    simplyilka - February 21, 2014

    I am glad you are happy about this Sweetheart! ! You did a great job and can be really proud of yourself 🙂

Tamara - February 21, 2014

I am really happy you posted this mom

hitandrun1964 - March 2, 2014

Great post and she’s so cute. 🙂 We need a lot more female scientists so I hope she stays interested:)

    simplyilka - March 2, 2014

    Thank you so much! Yes, I hope she stays interested. It is still not that easy to be a full time scientist and having a family. But she definitely has the talent and a strong will 🙂

Ella - June 27, 2014

Hi Ilka!

How sweet is this! It’s really simple to do and simple to understand. And yet, it’s pure science.

    simplyilka - June 29, 2014

    Thanks Ella!

    Yes, even pure science can be understood 🙂

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