Drop Testing "Unbreakable" Ice (Pykrete)

Why It Matters

The results illustrate how simple, low‑cost fillers can substantially boost the toughness of ice-based composites, informing practical experiments in impact‑resistant frozen materials and small‑scale material science; however, limitations under higher energy impacts highlight constraints for real-world structural use.

Summary

A DIY materials test examined Pykrete—frozen water mixed with fillers—by subjecting dozens of lab-made samples to hammers, a pellet gun and a 6‑lb drop rig. Small wood particles (sawdust) markedly improved impact resistance versus plain ice, and various fillers (iron filings, diaper polymer, cotton/toilet paper) also increased toughness and energy absorption; traditional wood pulp performed no better than sawdust. Tests showed many composites could stop low‑energy pellets and deflect impacts without shattering, but larger impacts still cause failure and plain ice remained brittle. The creator iteratively refined sample size and filler type to map which additives most improve frozen composite resilience.

Original Description

I spent three months of my life trying to figure out pykrete—basically ice with wood pulp mixed in—how it works and how I could make it better. I still don’t know how it works, but I definitely made it better. And to prove it, I went to the top of the American Chemical Society building to push blocks of ice off the side.

Producers:

Andrew Sobey

Elaine Seward

Writer:

George Zaidan

Hosts:

George Zaidan

Executive Producer:

Matthew Radcliff

Scientific Consultants:

Brianne Raccor, Ph.D.

Michelle Boucher, Ph.D.

Executive in Charge for PBS: Maribel Lopez

Director of Programming for PBS: Gabrielle Ewing

Assistant Director of Programming for PBS: John Campbell

Reactions is a production of the American Chemical Society.

© 2025 American Chemical Society. All rights reserved.

Sources:

https://docs.google.com/document/d/1hFmqkdGYpPXmOyF_n7VabN0gd4AII0UolcuJKl5xol8