Are these safe to make with children?

Yes, with supervision and non-toxic materials. Choose child-safe glue and avoid small beads or anything a child might swallow. Let an adult handle sealants or resin. The tactile parts are safe and calming, and children often love the slow reveal of color.

How long do they take to fully dry?

That depends on size and humidity. Small pieces often cure in 24 hours. Larger or denser urchins can take up to 48 hours. A slow, even cure makes stronger pieces, so resist the urge to rush the drying.

Can I make them waterproof?

You can add a topcoat of clear resin or a marine-grade sealant for waterproofing. Work in a ventilated space and follow safety directions on the sealant. Clear craft glue gives some protection but is not fully waterproof.

What if the spines fall off?

If a spine breaks, glue it back gently with a small dab of clear craft glue and let it dry. For missing spines, you can add tiny rolled cones of paste and seal them. Over time, a little mending becomes part of the craft's charm.

How do I keep colors from fading?

Use liquid watercolors or stable pigment inks and avoid prolonged direct sunlight. A gentle topcoat also helps preserve color.

Rainbow Crystal Urchins Science Craft 2026

Rainbow Crystal Urchins

Print Recipe

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

No reviews

Create small, luminous Rainbow Crystal Urchins that reflect light and add charm to your space.

Author: margaret-ellis
Prep Time: 15 minutes
Cook Time: 30 minutes
Total Time: 45 minutes
Yield: 4 urchins
Category: Crafts
Method: Crafting
Cuisine: N/A
Diet: N/A

Ingredients

Baking soda or sodium bicarbonate
Table salt or Epsom salt (optional)
White glue (gentle sheen)
Clear craft glue or resin (optional)
Food coloring or liquid watercolor
Small silicone molds or cups
Fine glitter or iridescent mica powder (optional)
Small paintbrush or toothpick
Measuring spoons and a mixing bowl
A shallow tray or plate
A lightweight wire or tiny loop (optional)
Clear drying spray or sealant (optional)

Cook Mode Prevent your screen from going dark

Instructions

Prepare your workspace.
Mix the base paste by stirring 2 parts baking soda with 1 part white glue.
Color small batches by adding drops of liquid color.
Shape the urchin forms into molds or onto a nonstick surface.
Create texture using a toothpick to add indentations for spines.
Add sparkle by lightly dusting them with mica or glitter.
Let the pieces dry slowly in a warm, dry spot.
Seal them using clear craft glue or resin.
Add hanging loops if desired.
Rest and admire your finished pieces.

Notes

Substitute-friendly options and safety protocols are included. Non-toxic materials are recommended for children.

Find it online: https://www.cozyhandsdiy.com/rainbow-crystal-urchins-science-craft/