Shane Dumbell, New Plymouth.

While camping one year we had trouble keeping things cool, milk, butter, cheese and meat, and flies were also keen to get our supplies. I found an old beer crate (or use a box with holes or a grate box, like a bird cage for instance). Place a shallow tray, like foil oven tray or old baking dish (use imagination anything that will hold water will do).

On top of the box/cage and pull a muslin bag over the lot and then hang this up in a cool shady place where there is a breeze, like under a tree or at least in shade. Now weight the muslin into the tray with some stones no bigger than say about fist size, and fill the tray with water.

Put your food items inside the box and let the Muslin fall down to cover the box and its contents. Hang all this on a previously prepared hook or wire or tree branch in the previously chosen shady place. The water will slowly wick down the muslin and keep it wet.

The action of the breeze through the shade will evaporate the water from the wet muslin and lower the temperature inside the food store box so much so that I guarantee the butter will go so hard you will not be able to spread it easily on your bread. If you walk through you wet washing hanging on the line, even on a hot day it is very cool, as long as it is wet, same principle.

To take this contraption to the next level fill a glass jar with water and stand it upside down into the pool of water in the tray, chicken feeder style, and you can leave your new fridge for hours unattended, bigger jar longer periods between filling. A fridge of the grid and good for camping as long as there is water in the tray.