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Make fizzy bath bombs by combining baking soda, citric acid, cornstarch, oil, and color; learn safe mixing, measurement, and simple chemical reactions.

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Step-by-step guide to make fizzy bath bombs

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What you need
Adult supervision required, baking soda, citric acid, coloring materials like food coloring or powdered color, cornstarch, gloves and safety goggles, measuring cup and measuring spoons, mixing bowl, paper towels, silicone molds or ice cube tray, small cup, vegetable oil or coconut oil, whisk or spoon

Step 1

Spread a paper towel on your table to protect the surface.

Step 2

Measure 1 cup of baking soda into the mixing bowl.

Step 3

Measure 1/2 cup of citric acid into the same mixing bowl.

Step 4

Measure 1/2 cup of cornstarch into the same mixing bowl.

Step 5

Whisk the three dry ingredients until they are evenly mixed.

Step 6

Measure 2 tablespoons of oil into the small cup.

Step 7

Add 6 to 10 drops of your chosen coloring into the oil in the small cup.

Step 8

Pour the colored oil slowly into the dry mix while holding the bowl steady.

Step 9

Stir the mixture until it feels like damp sand and clumps when you squeeze it.

Step 10

Pack the mixture firmly into each silicone mold so they are tightly filled.

Step 11

Tap each filled mold gently on the table to remove air pockets.

Step 12

Let the molds dry undisturbed for 24 hours so the bath bombs harden.

Step 13

Pop the bath bombs out of the molds and let them finish drying on a paper towel for 2 to 4 hours.

Step 14

Share your finished creation on DIY.org

Final steps

You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!

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Help!?

What can I use if I can’t find citric acid for the recipe?

If you can’t find citric acid, buy it online or substitute with 1/2 cup of cream of tartar as a less-fizzy alternative while keeping the 1 cup baking soda and 1/2 cup cornstarch the same.

My mixture won’t clump or is falling apart when I squeeze it—what should I do?

If the mixture won’t clump during the 'stir until it feels like damp sand and clumps when you squeeze it' step, add the colored oil dropwise (a few drops at a time) and remix, and if it becomes too wet, stir in a teaspoon of baking soda or cornstarch at a time until it firms.

How can I adapt this bath bomb activity for different ages?

For preschoolers, have an adult pre-measure the baking soda, citric acid, and cornstarch and let the child pour the colored oil and press the mixture into silicone molds, while older kids can measure ingredients themselves, experiment with essential oils, and try layered colors or different drying times.

How can we make or present the bath bombs more special or long-lasting?

To personalize and enhance the bath bombs, stir in a teaspoon of dried lavender or cosmetic-grade biodegradable glitter before packing each silicone mold, create layered colors by pouring different colored oil mixtures in stages, and let them fully dry before popping out and photographing to share on DIY.org.

Watch videos on how to make fizzy bath bombs

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Facts about home chemistry for kids

⚖️ Precise measuring matters: too much acid or base changes fizzing, texture, and how well the bomb holds together.

🎨 Adding oil and safe, cosmetic-grade color makes bath bombs smooth and pretty—but some dyes can stain skin or tubs.

🛁 Bath bombs fizz because sodium bicarbonate and citric acid react to produce carbon dioxide bubbles that make the fizz!

🍋 Citric acid is found naturally in lemons and other citrus fruits and gives them their sour taste.

🧪 Sodium bicarbonate (baking soda) is a gentle base used in baking, cleaning, and even as a mild antacid.

How do I make fizzy bath bombs with baking soda and citric acid at home?

Combine dry ingredients first: sift 1 cup baking soda, 1/2 cup citric acid, and 1/2 cup cornstarch into a bowl. In a separate small bowl, mix 2–3 tablespoons light oil and a few drops of color and optional fragrance. Slowly spritz a little witch hazel or water into the dry mix while stirring until it feels like damp sand. Pack firmly into molds, let dry 24–48 hours, then unmold and cure in a dry place before use, with adult supervision throughout.

What materials and tools do I need to make kid-friendly fizzy bath bombs?

You’ll need baking soda, citric acid, cornstarch, a light oil (coconut, almond, or vegetable), liquid (witch hazel or water), and skin-safe colorant or mica. Optional: a few drops of child-safe fragrance, silicone or plastic molds, measuring cups and spoons, mixing bowls, a whisk, gloves, and an airtight container for storage. Keep materials out of reach of small children and avoid food containers for storage to prevent accidental ingestion.

What ages are fizzy bath bomb projects suitable for?

With careful adult supervision, children aged 6 and up can participate in measuring, mixing, and molding. Older children (8–12+) can follow measurements more independently. Preschool children can help with safe tasks like pressing mixture into molds or choosing colors, but an adult should handle powders, liquids, and any fragrance. Always supervise to prevent ingestion and protect eyes and skin.

What safety tips should I follow when making bath bombs with kids?

Always supervise closely: avoid inhaling powders, wear gloves if skin is sensitive, and keep ingredients away from eyes and mouths. Add liquids slowly to prevent premature fizzing. Use child-safe colorants and mild or no fragrance for young children, and patch-test on skin. Store finished bombs in an airtight container out of reach. Clean up spills right away and never allow children to taste any ingredients.
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Chemically manufacture a product. Activities for Kids.