These days, we’re surrounded by modern technologies that are easy to take for granted. Consider refrigerators, and compare that with this: the Australian Coolgardie safe widely used just about 100 years ago. The key difference is this old cool box cooled food before electricity was widely available.
How? What if I told you the answer involved this cool box design, trees, and humans? Does it use timber keep food cold? Not quite. Rather, this invention cools its interior through evaporation, and it’s this principle that makes it similar to trees and us humans!
Capillary Action
Why does evaporation work, though? The answer depends on capillary action and the Australian outback climate. Fabrics like hessian and flannel would be draped down and kept wet by a tray or tank of water dripping down from the top of the safe. The porousness of the fabric encourages the water to spread throughout and surround the mesh metal walls of the safe. Like moisture-wicking clothes, the roots and branches of trees, and our skin, the Coolgardie safe works on capillary action and evaporation.
Australian Outback Climate
The second part of the equation is air flow, and hot, dry winds are best. That’s because heat helps the water to evaporate. Also, the air being dry usually means it has some “free space” to hold more humidity from water molecules. The stronger the wind, the lower the humidity tends to be. Water vapour, being a gas, needs heat energy to keep its molecules spread out in the air. As the molecules absorb heat, the air inside the safe cools, and so too does the food.
A Resourceful Implementation of Evaporative Cooling
While food safety regulations today require much colder temperatures, the Coolgardie safe was useful for at least slowing down food spoilage and keeping it away from pests and wild animals. And even though ice chests were gaining popularity in some cities, the Coolgardie safe remained a mainstay for much of the early 1900s before refrigerators became affordable enough in the 1950s. “Necessity is the mother of invention”, as they say, and invent they surely did!
William Hartono
Collection Stories Volunteer