Slime

Cross-linked polymer demonstrating non-Newtonian behavior

Difficulty: Very Easy | Time: 10 minutes | Visual Impact: High

Historical Context

The slime we know today was accidentally invented in 1976 by Mattel employee Marvin Belmore while trying to create a rubber substitute. The product, sold as “Slime” in a small plastic trash can, became a cultural phenomenon.

The chemistry, however, was understood earlier. Polyvinyl alcohol (PVA) was first prepared in 1924, and its cross-linking with borate ions was studied in the 1940s. The resulting material is a classic example of a non-Newtonian fluid - it behaves like both a liquid and a solid depending on how it’s handled.

Slime became a staple of chemistry education because it demonstrates polymer chemistry in a tactile, memorable way. The “gross” factor makes it especially appealing to children, who learn about cross-linking while playing.

Materials

  • PVA glue (white school glue) - 120mL (about 4 oz)
  • Borax - 1 teaspoon (5g) dissolved in 120mL warm water
  • Water - 120mL
  • Food coloring - 3-4 drops (optional)
  • Two containers

Procedure

  1. Mix 120mL glue with 120mL water in first container, add food coloring
  2. In second container, dissolve 5g borax in 120mL warm water
  3. Slowly pour borax solution into glue mixture while stirring
  4. Slime forms immediately - knead for 2-3 minutes until desired consistency
  5. Store in sealed container

The Science

Borate ions cross-link the long PVA polymer chains, creating a viscoelastic material that’s both liquid and solid:

  • PVA glue contains long polymer chains that can slide past each other (liquid behavior)
  • Borate ions form temporary bridges between chains (cross-linking)
  • The bridges constantly break and reform, giving slime its unique properties

This creates a non-Newtonian fluid: - Pull slowly → flows like liquid - Pull quickly → snaps like solid - Roll into ball → bounces - Let sit → flows flat

Variations

  • Fluffy slime: Add shaving cream before borax
  • Magnetic slime: Add iron oxide powder
  • Glow slime: Add glow-in-the-dark paint
  • Crunchy slime: Add foam beads

Safety

Borax has low toxicity but should not be eaten. Wash hands after playing. Not recommended for very young children who put things in their mouths.

Resources