How to Make Slime: 6 Easy Recipes (5 Without Borax)

Slime is one of the most satisfying sensory experiences for children. It stretches, it oozes, it drips through fingers and makes the most satisfying noises. It is also a surprisingly good chemistry lesson: every slime recipe is a different way of tangling long molecules together.

Most slime recipes online use one activator: borax, or contact lens solution that contains boric acid. Those make the stretchiest slime, but they are not for toddlers or for kids who still taste everything. So below you will find six recipes: one classic glue slime, and five that use no borax or boric acid at all, made from kitchen ingredients like psyllium, chia seeds, gelatine and marshmallows.

And because it is autumn, every recipe also has a spooky name. Ghost slime, monster snot, frog-spawn potion... Pick your favourite, or make them all and run a slime lab. More seasonal experiments wait in our Pumpkins & Potions lab.

Which slime should you make?

"Taste-safe" means a lick or a nibble won't hurt. It still shouldn't be eaten in large amounts, and small add-ins like googly eyes, beads or glitter are choking hazards for children under 3.

The science of slime: polymers

Everything slimy has one thing in common: polymers. A polymer is a super long molecule made of thousands of small pieces joined in a chain, like a string of paper clips.

When polymer chains float around freely, they slide past each other and the liquid flows, like cooked spaghetti sliding off a fork. When the chains get tangled or linked together, they form a loose net. Water gets trapped inside the net, and that makes the liquid stay together, stretches and wobbles.

The recipes below just use different polymers and different ways of building that net:

• Glue slime: the glue's plastic chains get linked by tiny cross-links (A link that joins two long polymer chains together, turning a runny liquid into a stretchy net.) made by the activator.
• Psyllium and chia: plant fibres soak up water and form a slippery gel called mucilage (A thick, slippery gel that some plants and seeds make from long sugar chains when they soak up water.). That is why soaked chia seeds feel like frog eggs.
• Gelatine and marshmallows: a protein from animal collagen unwinds in hot water, then twists back into a tangled net as it cools.

The bonds in slime are not permanent. They keep breaking and re-forming, which is why slime can stretch slowly, drip and puddle, but snaps when you pull it fast.

1. Ghost slime (classic glue slime)

This is the stretchiest, longest-lasting slime and the best one for experimenting. It needs an activator with boric acid, so it is for children aged 5 and up who don't put things in their mouths.

You will need:

• 120 ml (1/2 cup) white PVA school glue
• 60 ml (1/4 cup) water (optional, for a softer slime)
• 1/2 teaspoon baking soda
• 1 tablespoon contact lens or saline solution that lists boric acid and sodium borate in its ingredients
• Optional: white glitter, food colouring, googly eyes

Steps:

1. Pour the glue into a bowl and stir in the water.
2. Mix in the baking soda. Add glitter or colouring now.
3. Add 1 tablespoon of the solution and stir. Watch the mixture start to pull away from the sides of the bowl.
4. Keep stirring, then knead with your hands. If it is still sticky after a minute of kneading, add a few more drops of solution. Go slowly: too much makes it stiff and rubbery.
5. For a ghost, leave it white. For eyeball slime, press in googly eyes and swirl in a drop of red colouring for "bloodshot" veins.

Why does it work? Glue is a polymer. The baking soda makes the mixture slightly basic, and that turns the boric acid from the contact lens solution into borate. Borate links the glue's polymer chains to each other in many places, building the net that makes slime.

Too stiff? Knead in a pea-sized bit of Vaseline or hand lotion. The oil gets between the polymer chains and makes the slime softer and stretchier again.

2. Monster snot (psyllium husk slime)

It looks and feels exactly like a giant's sneeze. A bit sticky and yucky and so much fun! It is made from psyllium husk, a plant fibre sold in pharmacies and health food shops as a digestive aid.

You will need:

• 1 tablespoon psyllium husk powder (or 2 tablespoons whole husks)
• 250 ml (1 cup) water
• Green food colouring
• A large microwave-safe bowl

Steps:

1. Stir the psyllium, water and a few drops of green colouring together in the bowl.
2. Adult step: microwave for 1 minute, stir, then repeat in 30-second bursts. The mixture bubbles up, so use a big bowl and watch it. After 3 to 5 minutes it becomes thick and gloopy. Alternatively, you can cook it in a small saucepan on the stove over medium heat, stirring constantly.
3. The longer you cook it, the firmer it gets. Stop earlier for runny snot, later for a bouncier slime.
4. Let it cool completely before anyone touches it. It stays hot inside for a while.

Why does it work? Psyllium fibre is a polymer made of long sugar chains. It soaks up water and forms mucilage, the same kind of slippery gel that makes okra and soaked flax seeds slimy. Heat speeds up the soaking.

3. Frog-spawn potion (chia seed slime)

Soaked chia seeds look like tiny frog eggs, which makes this the perfect witch's potion. It is also the safest slime for toddlers, as long as an adult is watching.

You will need:

• 3 tablespoons chia seeds
• 250 ml (1 cup) water
• 4 to 8 tablespoons cornstarch
• Optional: a drop of green or purple food colouring

Steps:

1. Mix the chia seeds, water and colouring in a bowl and leave for at least 30 minutes (or overnight in the fridge). The seeds swell and turn gooey.
2. Stir in the cornstarch one spoonful at a time, mixing with your hands.
3. Stop when it holds together and stretches but still oozes. Too stiff? Add a splash of water.

Why does it work? Each chia seed is covered in a thin coat of mucilage. In water it swells into a clear, slippery gel around every seed. The cornstarch thickens the watery part so the "eggs" stick together into one gooey blob.

4. Bloody jelly goo (gelatine slime)

Red, wobbly and gooey: the most dramatic slime of the six. Make it dark red and it looks a lot like fake blood, but it's made with the same gelatine you'd use for a jelly.

You will need:

• 1 tablespoon (about 10 g, one packet) unflavoured gelatine powder
• 120 ml (1/2 cup) hot water
• Red food colouring, plus one drop of blue or a pinch of cocoa to darken it
• Optional: 1 tablespoon corn syrup or glucose syrup for extra shine and stretch

Steps:

1. Dissolve the gelatine in the hot water, stirring until no grains are left.
2. Stir in the colouring (and syrup, if using).
3. Chill in the fridge for 15 to 25 minutes, checking every 5 minutes. You want thick and gooey, not set jelly. If it does set, warm it in your hands or for a few seconds in the microwave.
4. Squish, drip and stretch.

Why does it work? Gelatine is a protein that comes from collagen. In hot water its long chains unwind and float freely. As they cool, they start twisting back into coils that tangle together and trap water. Stop the cooling early and you get goo; let it finish and you get jelly. Gelatine melts at about body temperature, so the goo gets runnier the longer it is held in warm hands.

5. Mummy slime (marshmallow slime)

The one children are allowed to eat. Sweet, stretchy, gone in an afternoon. It's best for the youngest slime scientists.

You will need:

• 1 cup (about 50 g) mini marshmallows, white for a mummy
• 1 teaspoon vegetable oil
• 2 to 4 tablespoons cornstarch or powdered sugar

Steps:

1. Adult step: microwave the marshmallows and oil in a bowl for 20 to 30 seconds until puffed and soft. Melted sugar is very hot, so stir and test the temperature before letting children touch it. You can also melt the marshmallows in a small saucepan over low heat, stirring constantly.
2. Stir in the cornstarch or powdered sugar one spoonful at a time.
3. Knead on a surface dusted with more cornstarch until it stretches without sticking.
4. Pull it into long strips and wrap them around a toy as "mummy bandages".

Why does it work? Marshmallows are a foam of sugar held together by gelatine. Warming melts the sugar and the gelatine, so the marshmallow becomes a sticky, stretchy mass. Cornstarch soaks up the stickiness.

6. Pumpkin cloud slime (cornstarch and conditioner)

This one is somewhere between slime and dough: silky, soft and mouldable. It's perfect for little pumpkins, and a great bridge to oobleck, which also uses cornstarch.

You will need:

• 120 ml (1/2 cup) hair conditioner
• About 1 cup (120 g) cornstarch
• Orange food colouring (or red and yellow mixed)

Steps:

1. Mix the conditioner and a few drops of colouring in a bowl.
2. Add the cornstarch a little at a time, kneading as you go.
3. Stop when it feels like soft, smooth dough. Roll balls, press lines into them with a toothpick and add a green paper stem for pumpkins.

Why does it work? Cornstarch is a polymer too, packed into tiny grains. The conditioner coats the grains with oils and waxy ingredients, so they cling to each other but still slide. It smells lovely but isn't taste-safe, so it's best for children aged 3 and up.

Make it spooky

• Slime graveyard: hide plastic bones, spiders or gems in ghost slime and let children excavate them with tweezers.
• Eyeball jar: fill a clear jar with frog-spawn potion and push googly eyes against the glass.
• Slime potion shop: put each slime in a jar with a handwritten label ("Monster snot, 1 spoon per spell") and let children run the shop.
• Monster texture test: blindfold a grown-up and see if they can guess each slime by touch alone.

Questions to ask while you play

• Is slime a liquid or a solid? What makes you think so?
• What happens if you pull it slowly? And if you pull it fast?
• Which slime is the stretchiest? Which is the most gooey? Why might that be?
• Can you think of other slimy things in nature? (Snail trails, frog spawn, aloe vera.)

Frequently Asked Questions