Parnell Pitch Drop Experiment
2 million times thicker than honey
The “Parnell pitch drop” is the world-famous ultra-slow experiment at the University of Queensland that shows pitch (bitumen) isn’t truly solid at room temperature—it’s an extremely viscous liquid that flows so slowly a single drop takes years to form.
- In 1927, physics professor Thomas Parnell warmed pitch and poured it into a glass funnel, then let it settle. In 1930 he cut the stem to let it start “flowing.” Since then only nine drops have fallen; the most recent dropped in April 2014. The setup sits under a bell jar in a hallway, still creeping along. (School of Mathematics and Physics)
- The pitch’s viscosity is on the order of hundreds of billions of times that of water (UQ commonly cites ~100 billion; earlier measurements put it ~230 billion), which is why it looks solid even though it very slowly drips. Temperature changes nudge the rate a bit. (School of Mathematics and Physics, Wikipedia)
- It’s the Guinness-recognized longest-running lab experiment; Parnell and long-time custodian John Mainstone even received an Ig Nobel in 2005 for it. A live webcam now watches the funnel. (School of Mathematics and Physics)
Fun side note: a sister experiment at Trinity College Dublin finally captured a pitch drop on camera in July 2013—the first time anyone definitively filmed one falling. (Trinity College Dublin)
Here’s the University of Queensland (Parnell) pitch-drop timeline:
- 1927 — Pitch poured into sealed funnel
- Oct 1930 — Stem cut; flow begins
- Dec 1938 — 1st drop
- Feb 1947 — 2nd drop
- Apr 1954 — 3rd drop
- May 1962 — 4th drop
- Aug 1970 — 5th drop
- Apr 1979 — 6th drop
- Jul 1988 — 7th drop
- Nov 2000 — 8th drop
- Apr 2014 — 9th drop (touched the 8th on Apr 12; separated from the funnel during a beaker change on Apr 24). (Wikipedia)
Other milestones:
- 2005 — Parnell & long-time custodian John Mainstone receive the Ig Nobel Prize in Physics. (Wikipedia, Nature)
- Jul 11, 2013 — Trinity College Dublin’s sister experiment becomes the first to record a pitch drop on camera. (Trinity College Dublin, Nature)
- Status — UQ notes nine drops to date; the tenth was/ is expected sometime in the 2020s (none reported as of Aug 10, 2025). (School of Mathematics and Physics)