The Australian building and design industry measures the slipperiness of flooring surfaces by two units – the Sigler and the Tortus.
Percy Sigler designed the Sigler Pendulum Skid Resistance Test in the 1940s and motoring authorities around the world have since adopted the Sigler Pendulum Skid Resistance Test for quantifying tyre friction on road surfaces. The Sigler test involves swinging a pendulum at 2.7 metres-per-second across a surface and measuring the energy lost on its upswing after contact between the pendulum foot and the test surface.
The Torus Testing method, meanwhile, was designed by the British Ceramic Research Association. It involves moving a rubber disk across a surface with a velocity of 0.17 metres-per-second. Both are slip resistance value units (SRVs).
So, dear reader, we must be clear when we’re talking about slipperiness with regards to which index we’re referring to – the very same test will measure 0.52 Sigler (or ‘pendulum’) SRVs and 0.82 Tortus SRVs. Generally, a flooring surface – a tiled bathroom floor for example – with a measure of more than 0.4 Sigler units is regarded as satisfactory, as is a measure of more than 0.89 Tortus units.
On wet surfaces the Tortus method is regarded as inferior because its procedure does not involve enough speed to account for the effects of hydrodynamic film – aquaplaning.
It appears that quantifying slipperiness is an inexact science. The Greater London Council developed another method in 1971 – the GLC Test Criteria. And a Mr DI James developed yet another method in 1985. The ISO Standard En ISO 10545-17 describes various methods to measure the coefficient of friction, but none is universally accepted.
In TV cartoons, banana skins – known to be slipperier than ice – are integral to the best-hatched plans and booby traps. It’s hard to find a Looney Tunes production without a banana skin as part of the story arc. But next time you step around a banana skin on the footpath, please spare a thought for Percy Sigler and his important and pioneering work for the US National Bureau of Standards in the 1940s. You know Daffy Duck would approve.