DIY Baking Soda Galaxy Christmas Ornaments for Kids

My kids are obsessed with space — like, can-name-all-the-planets-and-will-correct-you obsessed. So when I found a craft that combines baking soda volcanoes with galaxy art and turns into Christmas ornaments, I knew I was in trouble (the good kind).

You mix baking soda, vinegar, and cornstarch into a dough, color it deep space blues and purples, cut out stars, and hang your own little galaxies on the tree. The fizzing when the vinegar hits the baking soda is half the fun. My son declared it "science you can hang up," which is going on his college application someday.

Why You'll Love Making These

This craft is two activities in one: first a fizzy science experiment that makes kids shriek with delight, then an art project with a gorgeous payoff. The dough is fun to squish, the colors are dreamy, and the finished ornaments look genuinely stunning on the tree.

They also make wonderful gifts. Handmade ornaments from kids are the kind of thing grandparents keep forever — ask my mom, who still hangs a lopsided clay star from 2019.

Materials You'll Need

• 1 cup baking soda
• 1/2 cup white vinegar
• 1/4 cup cornstarch
• Food coloring in blue, purple, and black (gel colors give the deepest galaxy shades)
• Mixing bowl and spoon
• Star or circle cookie cutters
• A straw or skewer (for poking the hanging hole)
• Parchment paper or a silicone mat
• Optional: fine glitter for stars, ribbon for hanging

Heads up: this is a fizzy, messy, glorious process. Cover the table and wear play clothes.

<img src="https://thediynook.com/wp-content/uploads/2026/09/pin-v1-22.webp" alt="Baking Soda Galaxy Ornaments" />

Step-by-Step Directions

1. Cover your work surface. I'm serious. This one gets enthusiastic.
2. Pour 1 cup of baking soda into the mixing bowl. Add the 1/2 cup of vinegar and watch it fizz — let the kids enjoy this moment fully.
3. Gradually stir in the 1/4 cup of cornstarch until a pliable dough forms. Knead it with your hands if it's stubborn.
4. Divide the dough into portions, one for each color. Add food coloring to each and knead until the color is even. (Gloves save little hands from a week of blue fingers.)
5. Marble the colors together lightly — twist the portions together once or twice for that swirly galaxy look. Don't overmix or it turns gray.
6. Roll the dough about 1/4 inch thick on parchment paper.
7. Cut out stars (or circles, moons, whatever cutters you have). Poke a small hole near the top of each with a straw for the hanging ribbon.
8. Transfer to parchment paper and let them air dry for 24 to 48 hours, flipping once halfway through. They need to be completely hard.
9. Optional: sprinkle glitter on while still slightly damp so it sticks.
10. Thread ribbon through the holes and hang them on the tree — or wrap them up as gifts.

The Learning Behind This Craft

The vinegar-and-baking-soda reaction is a classic acid-base chemistry demo, and kids never get tired of it. Measuring the ingredients practices math, kneading builds hand strength, and marbling colors is a hands-on lesson in how colors blend (and how to stop before they turn to mud).

Tips If Things Go Sideways

Dough too sticky? Add a little more cornstarch, a tablespoon at a time, until it's pliable but not tacky.

Dough too crumbly? A tiny splash of water — like, drops — brings it back together.

Ornaments cracking while drying? They dried too fast, or the dough was rolled too thin. Keep them at 1/4 inch and let them dry slowly away from heat vents.

Colors turned gray? The colors got over-mixed. Next time, twist the colored portions together just once or twice and stop.

Hole closed up while drying? Poke it again with the straw halfway through drying, while the dough is still slightly soft.

Fun Variations to Try

• Add a few drops of essential oil (peppermint, vanilla) for scented ornaments.
• Use moon and planet-shaped cutters for a full solar system set.
• Paint gold dots on the dried ornaments for extra stars.
• Make gift tags out of the smaller cutouts.
• Try metallic food coloring for a shimmery nebula effect.

FAQs

Can I use less vinegar?

Stick with the recipe — the vinegar amount affects the dough's texture and drying. This isn't the step to improvise on.

How do I store these after the holidays?

Wrap each in tissue paper and keep them in a rigid box in a cool, dry place. Moisture is the enemy — it softens them right back up.

Can these hang outside?

No — rain or humidity will ruin them. Indoor trees only.

How long do they take to dry?

24 to 48 hours depending on thickness and humidity. Don't rush it; a soft ornament will crack on the tree.