The Coolgardie safe is a

low-tech Low technology (low tech; adjective forms: low-technology, low-tech, lo-tech) is simple technology, as opposed to '' high technology''. In addition, low tech is related to the concept of mid-tech, that is a balance between low-tech and high-tec ...

food storage unit, using

evaporative cooling An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning sy ...

to prolong the life of whatever edibles are kept in it. It applies the basic principle of

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

which occurs during

evaporation Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

(see

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process—usually a first-order phase transition, like melting or condensation. ...

and heat of evaporation). It was named after the place where it was invented – the small mining town of

Coolgardie, Western Australia Coolgardie is a small town in Western Australia located around east of the state capital, Perth; and southwest of Kalgoorlie. It has a population of approximately 850 people. Although Coolgardie is now known to most Western Australians as a ...

, near

Kalgoorlie-Boulder Kalgoorlie-Boulder (or just Kalgoorlie) is a city in the Goldfields–Esperance region of Western Australia, located east-northeast of Perth at the end of the Great Eastern Highway. It is referred to as Kalgoorlie–Boulder as the surroundi ...

History

Coolgardie was the site of a

gold rush A gold rush or gold fever is a discovery of gold—sometimes accompanied by other precious metals and rare-earth minerals—that brings an onrush of miners seeking their fortune. Major gold rushes took place in the 19th century in Australia, ...

in the early 1890s, before the

gold rush. For the

prospectors Prospecting is the first stage of the geological analysis (followed by exploration) of a territory. It is the search for minerals, fossils, precious metals, or mineral specimens. It is also known as fossicking. Traditionally prospecting rel ...

who had rushed here to find their fortune, one challenge was to extend the life of their perishable foods – hence the invention of the Coolgardie safe. The safe was invented in the late 1890s by Arthur Patrick McCormick, who used the same principle as explorers and travellers in the Outback used to cool their canvas water bags: when the canvas bag is wet the fibres expand and it holds water. Some water seeps out and evaporates. It is most effective when air continually moves past it, such as when in a moving vehicle or when exposed to a breeze. This technology is commonly thought to have been adopted by explorer and scientist Thomas Mitchell, who had observed the way some

Indigenous Australians Indigenous Australians are people with familial heritage from, or recognised membership of, the various ethnic groups living within the territory of contemporary Australia prior to History of Australia (1788–1850), British colonisation. The ...

used kangaroo skins to carry water.

Principles of operation

The Coolgardie safe was made of wire mesh, hessian, a wooden frame and had a hot dip galvanised iron tray on top. The galvanised iron tray was filled with water. The hessian bag was hung over the side with one of the ends in the tray to soak up the water. Gradually the hessian bag, acting as a wick, would draw water from the tray by the process of

capillary action Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of external forces like Gravitation, gravity. The effe ...

. When a breeze came it would pass through the wet bag and evaporate the water. This would cool the air inside the safe, and in turn cool the food stored in the safe. This cooling is due to the water in the hessian needing energy to change state and evaporate. This energy is taken from the interior of the safe (metal mesh), thus making the interior cooler. There is a metal tray below the safe to catch excess water from the hessian. Some modern tests have shown that the interior of the safe would achieve temperatures 3–9 °C (dependant on breeze) cooler than the atmospheric temperature during the middle of the day. {{cite web , last1=Durrant , first1=Jacqui , title=How effective is the 'Coolgardie safe'? , url=https://lifeonspringcreek.com/2017/02/10/coolgardie-safe/ , website=About Books & Papers Public Talks Contact Life on Spring Creek , access-date=24 May 2024 It was usually placed on a

veranda A veranda (also spelled verandah in Australian and New Zealand English) is a roofed, open-air hallway or porch, attached to the outside of a building. A veranda is often partly enclosed by a railing and frequently extends across the front an ...

where there was a breeze. The Coolgardie safe was a common household item in Australia until the mid-twentieth century. Safes could be purchased ready-made or easily constructed at home. Some of the metal panel safes are highly decorated.

References

Australian inventions Cooling technology Food preservation Appropriate technology Coolgardie, Western Australia

History

Principles of operation

See also

References