Historical information

Athol Hodgson began testing of retardants in 1963 at Ballarat by dropping water thickened with bentonite clay directly from a Ceres CA-28 aircraft.
In 1965 dropping a new chemical retardant Phoschek was produced by Monsanto
All this experimental work culminated with two Piper Pawnees from Benambra, flown by Ben Buckley and Bob Lansbury, making Australia’s first operational drop of fire-retardant on a small lightning-strike on 6 February 1967.
The flight at Benambra came to symbolise the classic application of firebombing and a "proof-of-concept" that encouraged many more innovations with new and more powerful aircraft.

Physical description

Fibreglass funnels used to measure the viscosity of the fire retardant, Phoscheck
The funnel was filled with liquid and timed to run through between 35 and 50 seconds