Bubbling Halloween Slime Recipe (Witch's Brew)

Make a bubbling Halloween slime recipe that fizzes, erupts, and stretches! This spooky witch’s brew combines homemade slime with a baking soda and vinegar reaction for a fun Halloween science experiment.

Inspired by the bubbling cauldron in Hocus Pocus, this Halloween slime lets you explore chemistry while making something wonderfully messy! Or if you like the Practical Magic movies, this works too.

Bubbling Halloween Slime

What makes this Halloween slime different? It bubbles and erupts before turning into stretchy slime!

The baking soda and vinegar create a chemical reaction that releases carbon dioxide gas, producing the bubbling, fizzing effect. Meanwhile, the glue and saline solution work together to form stretchy slime.

Explore: Chemical reactions, gas production, and polymers.

Ask: What happens when you change how much vinegar you add to the slime?

Supplies for Halloween Slime

1/2 cup Elmer’s Washable White School Glue
1 tablespoon saline solution (containing boric acid and sodium borate)
2 tablespoons baking soda
1/4 cup white vinegar
Green food coloring (or another Halloween color)
Small plastic cauldron or container
Small cup for mixing
Spoon or craft stick
Cookie sheet or craft tray
Plastic spiders or other creepy decorations (optional)

💡 Slime Tip: We used a small 5-inch black cauldron. Choose a container with enough room to stir and a relatively narrow opening for a more dramatic eruption. Place it on a tray to catch the overflowing slime!

This recipe uses our saline solution slime method. Not all saline solutions work for slime, so check the ingredients before you start.

How to Make Bubbling Halloween Slime

STEP 1: Add the white school glue and baking soda to your cauldron. Stir until thoroughly combined. Add a few plastic spiders or other Halloween decorations if desired.

STEP 2: Add several drops of green food coloring and stir. Purple or orange also makes a fun Halloween slime color!

STEP 3: In a separate small cup, combine the vinegar and saline solution.

STEP 4: Pour the vinegar-and-saline mixture into the glue mixture and stir.

🔎 Watch as your witch’s brew bubbles, fizzes, and rises out of the cauldron! This is why you’ll want a tray underneath.

STEP 5: Keep stirring as the bubbling slows. The mixture will gradually thicken and start forming slime.

STEP 6: Remove the slime from the container and knead until it becomes stretchy.

💡 It may feel messy or sticky at first. If needed, add a few drops of saline solution to your hands and keep kneading. Avoid adding too much extra saline solution, which can make the slime stiff and rubbery.

💡 Slime Safety: This recipe is not taste-safe. Keep slime away from mouths and eyes, wash hands afterward, and supervise slime making as appropriate for your group.

The Science Behind Bubbling Slime

This Halloween slime combines two fun chemistry activities in one!

Baking Soda and Vinegar Reaction: When baking soda and vinegar mix, they release carbon dioxide gas. The gas creates bubbles that push the mixture upward and out of the cauldron.

Slime Polymers: School glue contains long chains of molecules called polymers. The borate ingredients in the saline solution connect these chains, creating slime’s stretchy texture.

As the bubbling reaction slows down, the slime begins to come together. Keep stirring and kneading to see how its texture changes.

👉 Learn more about baking soda and vinegar experiments and homemade slime recipes.

Try a Bubbling Slime Experiment

Want to explore the science a little further? Try changing one thing at a time and comparing the results.

Change the vinegar: Does adding more or less vinegar change how much the mixture bubbles?
Compare containers: Does a tall, narrow cauldron produce a different eruption than a wide bowl?
Observe the texture: How does the mixture feel before and after the bubbling reaction?

Ask: What could you measure or observe to compare two bubbling slime reactions?

💡 For the best comparison, keep the other ingredients and conditions the same.

Free Halloween Slime Printable

Want a Halloween slime activity you can print and use right away?

Grab the FREE Halloween Slime Challenge for even more spooky slime-making fun.

👉 GET THE FREE HALLOWEEN SLIME PRINTABLE

Printable Halloween Slime Pack

Take your Halloween slime activities further with our Halloween Slime Pack, filled with seasonal recipes plus simple science, math, and printable activities.

You’ll find: