TEACHER RESOURCE – THE AUSTRALIAN COLONIES
Colonial Western Australian History –
Study of the Swan River Colony 1827 to 1890s
TEACHER RESOURCE 3
PENINSULA FARM: USING HEAT TO COOL – THE COOLGARDIE SAFE AND THE
CELLAR
On display in the Hardey homestead is a simple cooling device known as a Coolgardie Safe.
While it was not used in the original house, it is there to illustrate the scientific principle Joseph
Hardey used to extend the life of perishable food:
Evaporation is a cooling process. Water needs energy to change state from a liquid to a gas
and takes this energy in the form of heat from its surroundings.
People have been unknowingly using this principle for centuries. Early European explorers and
travellers in Australia used canvas water bags, where some water seeped out and evaporated,
in the same way Aboriginal people used kangaroo skins to carry water.
Arthur Patrick McCormick is credited with inventing the Coolgardie Safe while living in the gold
boom town of Coolgardie in Western Australia’s arid eastern interior. Fresh food was scarce and
expensive so to keep it cool in the extreme heat, McCormick placed his provisions in a box
covered with a wet hessian bag. He had observed how a wet bag around a bottle cooled its
contents; if the bottle was in a draught the bag would dry out more quickly but the contents
would be cooler.
Others adopted this invention and made improvements, some were manufactured commercially.
A model sold by Boans, the large Perth department store, had a rectangular metal frame with
hessian sides. Water was poured into a galvanized iron tray on top of the frame and strips of
flannel hung from the tray; due to capillary action, water from the flannel strips would drip down
onto the hessian sides, keeping them damp. A breeze would evaporate water in the hessian
and to become a gas the liquid took energy from the interior of the ‘safe’, cooling the air inside.
The Peninsula Farm cellar or cool room predates the invention of the Coolgardie Safe, but
works on the same principle: a trough runs around a below ground cellar and a tap in one
corner could be opened to fill the trough with water. The tap was connected by a pipe to an
outside well. Hessian bags hanging down from the trough drew in and held water when the
fibres expanded. The evaporating water took energy (heat) from the room’s interior, cooling the
perishable food stored on the cellar shelves.
Note: There is no connection between the word ‘cool’, meaning to keep food chilled and the
name of the goldmining town of Coolgardie. One version of Coolgardie’s naming has the first
warden on these goldfields asking the indigenous people the name of the local gnamma or
waterhole and Coolgardie being the anglicized version of this name.
© National Trust of Australia (WA)
Page 1 of 3
STUDENT ACTIVITY: Make a Coolgardie Safe
Students can investigate the cooling effects of evaporation and /or make a Coolgardie Safe:
From: http://museumvictoria.com.au/pages/2619/house-secrets-school-based-activities.pdf
http://scienceworks.museum.vic.gov.au/education/
Aim:
Make a model Coolgardie Safe that keeps things cool in hot weather.
What you need:
• Washed milk carton
• Rubber bands
• Scissors
• Hessian material
• Strips of cloth
• Stapler
• Sticky tape
• Thermometer
• Electric fan (optional)
• Water
What to do:
1. Cut the top from the carton at about 2 cm below the base of the sloping bit.
2. Staple the top, seal with sticky tape.
3. Cut 5cm x 10cm rectangles from each side of the carton.
4. Wrap a 30cm x 12cm rectangle of hessian around the sides, hold in place with rubber
bands or staples.
5. Invert the top and sit it in the top of the safe.
6. Fill the top tray with water, use strips of cloth to draw water onto the hessian
7. Test the safe, using the fan and thermometer.
© National Trust of Australia (WA)
Page 2 of 3
Questions
1. Describe what happens to the temperature inside the safe when air flows around it.
2. Describe the process that causes the temperature to do this.
3. Where does the energy needed to change water from a liquid into a gas come from?
Cooling effects of evaporation
From: http://scienceworks.museum.vic.gov.au/education/
Aim
Investigate the cooling effects of evaporating water.
What you need
• Empty drink can
• Cotton cloth
• Rubber bands
• Plate
• Thermometer
• Electric fan
• Water
What to do
1. Wrap the cotton cloth around the can, hold it in place with the rubber bands.
2. Stand the can on the plate.
3. Wet the material by adding water to the plate (observe the capillary action that forces
the water up the material.)
4. Place the thermometer in the can.
5. Blow air across the can using the fan.
6. Record the temperature inside the can every minute for ten minutes.
7. Plot a graph of how the temperature inside the can changed with time.
Questions
1. What happened to the temperature inside the can?
2. Suggest a reason why the temperature did this.
3. Describe how you feel on a hot windy day when you get out of a swimming pool.
4. Where does the energy needed to change water from a liquid into a gas come from?
© National Trust of Australia (WA)
Page 3 of 3