Green Leprechaun Slime for St. Patrick’s Day

Make green leprechaun slime for St. Patrick's Day.
Make green leprechaun slime for St. Patrick’s Day. (photo: Nevit)

Customize the classic slime recipe by making green leprechaun slime to celebrate St. Patrick’s Day. The slime isn’t sticky, so it won’t work as a leprechaun trap, but the vibrant green color may lure them close. It’s a fun holiday chemistry project for kids of all ages.


Leprechaun slime uses the classic borax and glue slime recipe:

  • 4-ounce School glue
  • Borax
  • Water
  • Green food coloring

Make Leprechaun Slime

Make two solutions. When they are mixed together, the molecules cross-link or polymerize the ingredients, making a slime or gel.

  • Stir borax into 1/2 cup hot water until no more dissolves. It’s okay if the solution is cloudy or there is a little bit of powder at the bottom of the container. Just add the liquid part to the recipe.
  • Mix all the glue (4 ounces) into 1 cup of water. If you use translucent glue, you’ll get translucent slime. If you use opaque white glue, you’ll get opaque slime.
  • Add a few drops of green food coloring to either solution. For a radioactive green color, add a bit of yellow food coloring. If you have golden coins or other small St. Patrick’s Day items, you can add them, too.
  • Use a spoon or your hand to make the slime. Mix 1/3 cup of the borax solution with 1 cup of the glue solution. You can add more borax or glue solution to change the consistency of the slime.

Make Glowing Leprechaun Slime

Leprechauns may like the slime even more if you make it glow (although this may be a myth)! Add a bit of yellow highlighter ink to the slime to make it glow brightly under a black light. For slime that really glows in the dark, use glow-in-the-dark paint or powder instead of food coloring. Expose this slime to bright light before turning out the light for the best effect. Don’t break open a glow stick because other chemicals in the slime will stop the chemical reaction that makes it glow so it won’t work.

How Leprechaun Slime Works

Polyvinyl acetate in glue reacts with borax in a chemical reaction. The borax forms cross-linking chemical bonds between the vinyl alcohol molecules, forming a flexible polymer. Specifically, hydrogen bonds form between the hydroxyl groups of the glue and the borate ions from the borax. This makes slime less sticky than glue because the glue sticks to itself and not other surfaces. The cross-linking forms a sort of net that traps water molecules. This makes the slime slimy and fluid. Because the molecules are flexible and not fixed, slime stretches before breaking. Varying the amount of glue or borax changes the properties of leprechaun slime, making it stickier (more glue) or firmer (more borax).

Mixing glue and borax forms cross-links between vinyl alcohol molecules, making a flexible polymer.
Mixing glue and borax forms cross-links between vinyl alcohol molecules, making a flexible polymer. (Smokefoot)

Storage and Clean-Up

Unfortunately, leprechaun slime won’t last until the next St. Patrick’s Day, but if you seal it in a plastic bag or bowl, it stays good for a few days. Refrigerating the slime extends the fun for several weeks.

While clear slime doesn’t stain clothes or surfaces, green leprechaun slime contains food coloring that will dye everything it touches. Slime washes away with warm, soapy water. Stains are easily removed with bleach.

St. Patrick's Day Science Experiments

St. Patrick’s Day Science

Find more fun and interesting St. Patrick’s Day science experiments.

More St. Patrick’s Day Science

Looking for more St. Patrick’s Day science? You can make leprechaun slime without borax. Or, mix it up and make green fire or glowing green flowers!


  • Cassassa, E. Z.; A. M. Sarquis; C. H. Van Dyke (January 1986). “The Gelation of Polyvinyl Alcohol with Borax”. Journal of Chemical Education. 63 (1): 57. doi:10.1021/ed063p57
  • Parratore, Phil. Wacky Science: A Cookbook for Elementary Teachers. Dubuque, Iowa: Kendall Hunt. p. 26. ISBN 0-7872-2741-2.