SYDNEY (AFP) - The science professor who oversaw the world's longest running laboratory test - the Pitch Drop Experiment - has died after more than half a century on its watch, his university said Monday.

Mr John Mainstone, the former head of the Department of Physics at the University of Queensland, was in charge of the experiment which demonstrated the fluidity and viscosity of pitch, a tar derivative once used to waterproof boats.

The experiment, established in 1927 by Professor Thomas Parnell, was designed to show that pitch, although it feels solid and can be shattered by a hammer blow at room temperature, acts like a fluid and flows through a glass funnel over time.

It took three years for the pitch to settle and then the glass funnel holding the substance was cut to allow it to flow out.

In the 83 years since then, only eight drops of pitch have fallen and no one has seen one actually fall, the university said.

Earlier this year Mainstone, who died last week aged 78 after suffering a stroke, said it looked like the next drop would fall before the end of 2013.

"It's got a mind of its own and in blink of an eye it can drop," the professor, who had monitored the tar's glacial movements for 52 years, told the Australian Broadcasting Corporation.

The head of the School of Mathematics and Physics at Queensland University Halina Rubinsztein-Dunlop, said Mainstone would be greatly missed.

"Professor Mainstone's dedication to the long-running experiment well past his official retirement ensured that media, researchers and undergraduate students had easy access to relevant information and an understanding of the important science behind it," she said.

"John's death is particularly sad as in his time as the custodian of the experiment, he did not see a single drop fall," she added.

The experiment is under constant surveillance, with three webcams trained on it to capture the ninth drop's fall on camera.