How to Make Silly Putty Using Silicone and Zinc

A 1944 chemical process for turning liquid silicone oil into a bouncy, stretchable, putty-like material by adding boron compounds and zinc hydroxide.

What it covers

The patent describes a three-step chemical process to create a unique elastic material. First, you heat liquid dimethylsiloxane with a boron-based catalyst, such as boric acid or borax, until it transforms into a solid, rubbery substance. Second, you incorporate a finely divided inorganic filler along with 12 percent zinc hydroxide by weight. Finally, you knead this mixture until it reaches a specific consistency that is both putty-like and elastic, allowing it to bounce like a ball or stretch like taffy.

What it doesn't cover

• —Does not cover the use of non-silicone base polymers for creating elastic putty.
• —Does not cover processes that exclude the specific addition of zinc hydroxide as a hardening or stabilizing agent.
• —Does not cover liquid silicone compositions that have not been processed into a solid, elastic state via boron heating.

The clever bit

The innovation lies in using zinc hydroxide as a specific additive to stabilize the silicone-boron matrix, preventing the material from becoming too sticky or losing its shape over time.

Why it matters

This patent captures the early development of silicone-based elastomers, which became the foundation for materials like Silly Putty. It represents a significant moment in polymer science where chemists learned to manipulate silicone chains to create materials with strange, non-Newtonian physical properties.

Real-world examples

• 1.Silly Putty
• 2.Bouncing putty toys
• 3.Early silicone-based industrial sealants