Cornflour Slime. How to make and what not to do!

Aug 8, 2013

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Cornflour Slime (or Cornstarch Slime) is a favourite activity of teachers and parents around the world. 

It is very popular as it's incredibly easy to make, doesn't use any nasty chemicals and has amazing properties unlike anything you may have experienced before. 

It is sure to delight young and old alike!

This is a great activity to introduce your kids to the concepts of  fluids and solids, because unlike most fluids (which are something that can flow), when applying pressure, this mixture acts like a solid. 

You can read more about the science behind why it does that, here and here.


  • Cornflour (Cornstarch)
  • Water
  • Large bowl and spoon
  • food colouring (optional)


Pour your cornflour (or cornstarch) into a large bowl. 

You will need at least double the amount of cornflour to water. (So, if you have 2 cups of cornflour, you'll add approx 1 cup of water, but experiment with this, that's the fun part!)

  • Add some food colouring to your water.

    What not to do: Do NOT add a lot of blue food colouring. Your hands will end up stained, like ours. You should use no more than 4-5 drops (my daughter added quite a bit more than this while I was photographing) and perhaps go with a green (most popular) or red.

  • Slowly add your water to your cornflour ensuring not to add more than half the amount of water to cornflour ratio.

  • Give it a stir part way through. This is a fun part of the experimenting. It allows the children to see what is happening at this point and make decisions as to whether more water is required or not.

They decided that more liquid was required!

Oooh, starting to get there!

Check out this solid lump we made!

You will know when your slime has all come together. It should be easy to stir slowly and flow like a liquid but try giving it a fast stir and see what happens!

Woah! What is big sister doing?

I've got to try this as well!

Can you catch it? Can you stop it from flowing?

Fun with slime

  • Part of the fun is getting the mix right so that you can form a solid (like a ball) that then turns into a fluid. Challenge children to roll a ball. Can they bounce it? Can they keep it from "melting" (lots of giggles here!)
  • If you can not form a ball, try adding a little bit more cornflour (cornstarch) until you can.
  • Try some of the experiments they do with their cornflour slime here.
  • Try adding some little plastic creatures like dinosaurs or insects to your slime to further the play. You could add plastic numbers or letters to further enhance the learning from this activity.

Handy Tips:

- If you missed our "What not to do" in the body of the post, it was in relation to using the colour blue and the amount of food colouring you need. 

We ended up with blue stained hands so if you want to avoid that, try using another colour or using no more than 4-5 drops of food colour. 

If you do happen to stain your hands, bicarb of soda should help you get the colour out of your skin.

- Keep a bit of cornflour (cornstarch) on the side so that if your over enthusiastic children tip in too much water, you will always have some extra cornflour to make the mix right.

Our slime ended up with a little bit more water than I would have liked but we just had to go with it as little N had already tipped in all of our remaining cornflour. Next time I will keep a bit extra on the side just in case.

- Cleaning up. This really isn't as terrible as it looks!

If you're really concerned about mess, try this activity outside or in a bathtub, otherwise, you will find that any little droplets that end up on the floor or table, dry out very quickly and can be easily swept or vaccumed up.

We really would have had very little mess if it wasn't for little N wanting to constantly wander off from the table with handfuls of dripping slime... but it really wasn't a big deal. :)

- You can keep your cornflour slime, covered in the fridge for a couple of days without it going bad.

You may need to add some more water and give it a good stir to reinvigorate it!

Check out some of our other Recipes for Play

Click the picture to go to the post
recipe for play  

Happy Playing,

Debs :)

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