The man who oversaw the world's longest running laboratory study, the University of Queensland's Pitch Drop Experiment, has died after suffering a stroke at age 78.

Professor John Mainstone died in his sleep in hospital last Friday with one of his daughters by his side, according to a university spokeswoman.

He had been cared for there by two cardiologists he once taught.

The former head of the Department of Physics monitored dripping tar from a glass funnel sitting in the lobby of the university's Parnell Building for 52 years.

The Pitch Drop Experiment was established in 1927 by Professor Thomas Parnell to demonstrate the fluidity and high viscosity of pitch, a derivative of tar once used to waterproof boats.

Professor John Mainstone Joined the University of Queensland as a Lecturer in Physics in 1961.

Joined the University of Queensland as a Lecturer in Physics in 1961. Became senior lecturer in 1966 and was promoted to Associate Professor in 1973.

Became senior lecturer in 1966 and was promoted to Associate Professor in 1973. Head of Department of Physics at UQ from 1989-1996.

Head of Department of Physics at UQ from 1989-1996. Research interests were in in the area of Physics of Atmosphere and Magnetosphere.

Research interests were in in the area of Physics of Atmosphere and Magnetosphere. Awarded Order of Australia: OAM in the General Division: Queen's Birthday Honours List in 2004.

Awarded Order of Australia: OAM in the General Division: Queen's Birthday Honours List in 2004. Custodian of the world's longest running laboratory experiment, The Pitch Drop Experiment, for 52 years.

At room temperature pitch feels solid and is brittle enough to be shattered with hammer, however when left sitting long enough can act like a fluid.

Three years after the experiment began, the glass funnel holding the pitch was cut to allow the pitch to "flow", according to the university.

Only eight drops have fallen in the 83 years since the pitch began dripping, and no one has ever seen one fall.

The experiment, which won Professor Mainstone and Professor Parnell an Ig Nobel Prize in 2005, needed no special attention apart from being kept at room temperature.

However, Professor Halina Rubinsztein-Dunlop, the head of the School of Mathematics and Physics, says Professor Mainstone's contribution outlived his tenure at the university.

"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 will be greatly missed around the halls of the Parnell Building at UQ where he maintained an office and a close connection with UQ until his death last week."

Referring to his famous experiment, Professor Rubinsztein-Dunlop added: "John's death is particularly sad as in his time as the custodian of the experiment, he did not see a single drop fall."

The experiment remains under constant surveillance, with three webcams providing a live feed from the university's School of Mathematics and Physics.

Professor Mainstone is survived by his wife Claire, daughters Julia, Penelope and Catherine, and his three grandchildren.