Heat is used up in the process of turning a liquid into a gas; that’s why we feel cooler as our sweat evaporates.
For centuries, people have used this principle to cool things down. Nowadays, the most common examples are wearing a wet hat to feel cool, using a wet canvas-covered water bottle or simply hanging a beer bottle in a wet sock to cool it down in a breeze.
Ancient porous terracotta pots kept drinking water cold by letting it evaporate through the sides. A wet pottery wine cooler or a pot-in-pot zeer filled with wet sand does the same thing.
Drinks covered in a wet cloth can be kept cool in a bucket half-filled with water.
Pockets like this wick up moisture to chill small items
A crude air conditioner can be made from a thin sheet wicking up moisture. Any breeze from a wind sail scoop, or fan, will be cooled.
The bilge is normally the coolest place for storage. Drinks can be chilled when you’re at anchor by submerging them in a net for a while. Mind you, in some parts of the world seawater temperatures can be pretty warm!H
Portable cool boxes stay cool longer in an insulated locker under a foam mattress.
Put ice packs at the bottom of the box and fill any air spaces with an old towel.
Frozen square bottles of water are good, but reusable ice packs stay colder for longer.
Frozen food takes a few days to thaw out in a well-insulated box, but do label things so you don’t leave the lid off too long while searching.
First-aid instant cold packs will chill things for an hour or so—but may contain poisonous chemicals, so care needs to be taken around food.
Some bluewater sailors cope without a fridge by keeping cheese in olive oil and “bottling” cooked food with a pressure cooker.
Dick Everitt has sailed thousands of miles in various parts of the world. He has been an illustrator, journalist and engineer for more than 40 years.