All shop-bought 'slime' will be packaged in plastic as well as containing plastic in the 'slime' itself. Some homemade 'slime' recipes call for PVA (plastic) glue, but it isn't necessary.
This homemade 'slime' is plastic free (if you choose plastic-free-packaged cornflour) and ready to use in a couple of minutes.
For enough slime to keep one child happy, you need...
1 cup (125g) cornflour (Brown & Polson branded cornflour is in just paper and cardboard).
1/3 cup (80ml) cold tap water .
That's it.
Just mix with a spoon (as best you can), add a small amount of food colouring gel if you want colourful slime and then play! You can adjust the runniness by adding a little more water / a little more cornflour. You know the consistency is correct when the cornflour slime in the bowl looks smooth and liquidy, but turns solid and flaky when you attempt to stir it quickly with a spoon or try and grab a handful. Spoons, measuring cups and playdough-prodders worked well as play implements.
The cornflour slime can be kept for a week in an airtight container in the fridge. Just add in a little more water if it dries out too much.
It will make a powdery mess wherever it is played with (but on the plus side it keeps kids - from toddlers to teens - enthralled for at least 30 minutes the first time they get their hands on/in the stuff). I always find that slime needs wiping-up-after twice with a damp cloth (rinsing the cloth in-between times) to get rid of the powdery traces.
As always, keep a close eye on young children when they are playing with / near liquids.
Please, please DON'T add glitter to your slime - regular glitter is ready-made microplastic litter and even eco glitter can contain traces of harmful-to-aquatic-life metals (it's what usually makes glitter sparkly).
Slime can be fun and eco friendly - yay!
The Science...
Making cornflour slime is an excellent practical activity if you want to talk about states of matter whilst having some hands-on fun.
Question: is it a solid? is it a liquid?
Answer: Cornflour slime is a liquid which sometimes acts like a solid.
Longer Answer: Cornflour slime is a 'non-Newtonian liquid' because it doesn't follow all the usual rules of liquids, which were described by the scientist Isaac Newton, around 400 years ago. If moved gently (such as when you gradually tip it from a container) the cornflour slime will flow like a liquid. If moved quickly or forcefully (try grabbing a handful and holding it tightly) then it suddenly turns into a solid lump. If you relax your handful of slime, then it will become liquid-like again and flow out of your hand.
The Reason: Under a microscope, the cornflour slime has large and jagged (rough) particles, meaning there are spaces between the particles - allowing it to flow like a liquid when it has plenty of space and time to do so. But if the jagged particles are squashed together by a sudden force, then they get snagged on each other and the slime acts (and feels) like a solid.
Real Life Uses: Body armour relies on this science. Bullet-proof vests are soaked in non-Newtonian liquid. This means that the material is flexible when the person wearing it is moving normally, but the material becomes hard and solid (and protects the body) when a sudden impact hits the vest.
A fun and educational plastic-free craft. Hurrah!