How to Make Erupting(Fizzing!) Slime at Home – A Fun STEM Activity for Kids

Slime is always a hit with kids (that’s why we have our simple slime and fluffy slime recipes!), but what if you could take it up a notch and make it erupt and fizz like a science experiment? Introducing – Exploding Slime! This bubbly slime is like the love child of two of our favorites – our color changing baking soda volcano and our classic slime. It takes the fun of sensory play with the wow of kid science to make, what I think, is one of the coolest at home projects. It’s anyone’s guess if my kids or I love this more?? Like… It’s probably them. But also, I am sitting there saying WOAH and CAN YOU BELIEVE THIS HAPPENED?? just as much as they are. And that’s when you know a project is a winner, I think.

Why Exploding Slime Works

This activity brings together two classic experiments: slime making and the great vinegar and baking soda reaction.

• The slime base forms from glue, baking soda, and saline solution.
• The eruption comes when you add vinegar, which reacts with the baking soda to release carbon dioxide bubbles. The slime foams, fizzes, and “erupts,” creating an exciting effect that kids love to watch.

Not only is it fun, but it also introduces kids to chemistry concepts like chemical reactions, polymers, and gas formation in an engaging, hands-on way.

Easy Way to Explain the Science to Kids

When explaining the science behind exploding slime, try keeping it simple and fun:

• The bubbles: Tell kids the fizzing and popping happens because vinegar (an acid) and baking soda (a base) are opposites. When they meet, they get super excited and make a gas called carbon dioxide, which shows up as bubbles.
• The slime: Explain that the glue has long chains of molecules, kind of like spaghetti noodles. When you add saline solution, it cross links the noodles, helping them stick together to make stretchy slime.
• The eruption: The vinegar reaction doesn’t just make bubbles—it pushes through the slime as it forms, which is why it looks like it’s erupting. Because the reaction needs to go through the cross linkage of the slime, this a slower reaction than a simple baking soda and vinegar volcano.

What You’ll Need

• ½ cup white school glue
• 2 tablespoons baking soda
• 1 tablespoon saline solution (contact lens solution with boric acid works best)
• ¼ cup vinegar
• A few drops of food coloring (any color you like! If you want to make a color changing volcano, make sure you have two colors)
• Mixing spoon and two bowls (one large, one small)

Step-by-Step Instructions

Step 1: Make the Glue Mixture

1. In a large bowl (or whatever you want your slime to erupt from), pour in the glue.
2. Add a few drops of food coloring and stir until evenly mixed.
3. Sprinkle in the baking soda and mix well.

This mixture forms the base of your slime.

Step 2: Prepare the Vinegar Solution

1. In a separate small bowl, pour in the vinegar. Add a few drops of your second food coloring if you’re going for a color changing reaction.
2. Stir in the saline solution until mixed.

This will be your “magic” fizzing activator liquid.

Step 3: The Fun Part – Make It Explode!

1. Slowly pour the vinegar solution into the glue mixture.
2. Watch as it bubbles, fizzes, and erupts! The baking soda reacts with the vinegar, producing carbon dioxide gas that escapes in foamy bubbles.
3. After the fizzing slows, you’ll be left with a gooey, stretchy slime you can knead into slime and play with. This can take a while. Before your slime is ready, the vinegar will all need to be neutralized by the baking soda. Be patient or you’ll have a real mess!

Don’t Use Too Much Vinegar

It’s tempting to add a lot of vinegar to make a bigger explosion, but there’s a science reason to be careful. The fizzing reaction only lasts as long as there’s baking soda available. Once the baking soda has been used up, extra vinegar has nothing left to react with.

When that happens, the leftover vinegar (an acid) can start breaking down the slime itself. The slime’s stretchy, gooey texture comes from polymer linkages formed between the glue and the saline solution. Too much acid disrupts those bonds, making the slime go from a fun cross linked play dough to a watery, sticky, and less fun to play with mess.

The good news is, if you’re looking for a way to clean up slime the easy way, vinegar is your answer! The bad news is, if you dump a ton of vinegar in expecting to see a giant fizzing slime volcano, you’ll actually end up with a puddle of not so fun goop.

For best results, stick to the recipe amounts. If kids want to see more fizzing, you can always repeat the experiment with a fresh batch rather than dumping in more vinegar.

Festive Holiday Twists

One of the best parts about exploding slime is how easily you can customize it for different holidays or themes!

• Halloween: Make “Witch’s Brew” by using spooky colors of food coloring and adding plastic spiders, bats, or glitter for a spooky bubbling cauldron effect.
• Christmas: Create “Santa Slime” with red and green food coloring, or sprinkle in some gold and silver glitter for a festive sparkle.
• Valentine’s Day: Use pink or red food coloring and add heart-shaped confetti for “Love Potion Slime.”
• Easter: Try pastel food colors (yellow, purple, or teal) and mix in tiny foam eggs or bunny confetti for a springtime fizz.
• Fourth of July: Use red, white, and blue coloring with star glitter for a patriotic science show.

Any of the miscellaneous items (spiders, confetti, glitter) should be added to the glue+baking soda base. Kids will love seeing how their slime changes for each season—it’s like a new activity every time!

STEM Learning Opportunities

While kids are having fun, you can sneak in some learning moments:

• Chemistry in action: Point out how vinegar (an acid) reacts with baking soda (a base) to form bubbles (carbon dioxide).
• Polymers: Explain how the glue contains long molecules that connect with the saline solution to form stretchy slime.
• Observation skills: Encourage kids to describe what they see, hear, and feel as the slime erupts.
• Color science: Use food coloring to explore complementary colors and color changes—try mixing two colors (one in the base and one in the vinegar activator solution) and observe how they combine into a new one.

Tips for Success

• Try different colors of food coloring to make rainbow explosions.
• Always supervise younger kids during the experiment (vinegar and slime can get messy!).

I know that slime can get messy and exploding slime adds an even bigger element of mess. But it’s a fun mess! And more than just a fun mess—it’s a STEM activity that mixes creativity, curiosity, and chemistry. With just a few simple household ingredients, a safe place for a mess, and a little bit of patience, you can turn an ordinary afternoon into an exciting science playtime! Worth the mess every time.