Gallery 3

Slow Flow

A perspex hour glass with a yellow synthetic rubber slowly flowing from top to bottom.
A large display case which has a perspex hour glass with a yellow synthetic rubber slowly flowing from top to bottom.

This synthetic rubber appears to be solid, but it behaves like a fluid.

How it works

In 1982, a synthetic rubber was placed inside a case and has slowly flowed and dropped over time due to gravity.

Things to try or ask around the exhibit

  • Is that synthetic rubber a solid or a fluid?
  • When did the rubber reach the bottom?
  • Does the rubber continue to flow today?


Fluids such as liquids and gases can flow. Some materials seem to be solid, but flow very slowly such as this synthetic rubber in the exhibit.

Some fluids flow readily, while others are more resistant to flow. This is measured as viscosity. Thick fluids that don’t flow easily (like honey or synthetic rubber) have high viscosity. Thin fluids (like water or gases) have low viscosity. Lava ranges from runny and fast flowing (low viscosity) to thick and slow flowing (high viscosity), depending on its temperature and how much silica it contains.

Finding the science in your world

Scientists currently think that the Earth’s inner core may be solid, its outer core may be fluid and its mantle may be solid (but flows gradually over millions of years, similar to the rubber).

Some stained glass windows in centuries-old churches have thicker glass at the bottom compared to the top. People once thought that the window glass had gradually flowed downwards to cause the thick bases. Scientists now believe that the glass did not flow downwards, but the windows were manufactured with thick bases to give the windows strength. Glass behaves like a solid, not a fluid at room temperatures.