Principles of Operation
The Coolgardie Safe was made of wire mesh, hessian, a wooden frame and had a 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 would get wet. When a breeze came it would go 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.
It was usually placed on a veranda 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, showing the creativity of their makers.
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