How do I keep food cold without a fridge?

Every list of tricks for this is longer than it needs to be, because most of the tricks are marginal and the real answer is a menu decision. Evaporative coolers, buried pots and streams all lower temperature by a few degrees, which is genuinely useful for keeping butter solid and nowhere near enough to make a chicken salad safe on day three.

Safety

Step by step

1. Start by changing the food, not the cooling.This is the whole answer for most people. Tinned fish and meat, dried pasta and rice, hard cheeses, cured sausage, UHT or powdered milk, long-life juice, eggs, bread, oats, nuts, dried fruit, tinned and fresh vegetables and most whole fruit need no refrigeration at all. Build the menu from those and the problem largely disappears.
2. Reserve the cool box for the few things that need it.Fresh meat for the first night, milk if you will not use UHT, and anything for the first day. Pack it properly — frozen mass, full box, cold on top, shaded, rarely opened — and plan to have used the perishable items by the time it warms.
3. Freeze the first days meals solid.Meat frozen flat in a bag, or a cooked meal frozen in a container, acts as a cold source while it thaws and is ready to cook by the time you want it. It is the most efficient use of a cool box there is.
4. Use evaporative cooling for what it can do.A damp cloth over a container in a breeze, a terracotta pot inside a larger pot with wet sand between them, or a bottle in a wet sock all cool by evaporation, and they work best in dry moving air. Expect a few degrees below ambient — enough to keep butter firm, vegetables fresh and drinks pleasant, not enough to make chilled high-risk food safe.
5. Use the ground and the shade.The coolest place on a campsite is shaded ground on the north side of something solid, ideally with a breeze. Digging a shallow pit in shade and standing containers in it is noticeably cooler than a table in the open. A stream, where genuinely clean and secured against being washed away, is cooler still.
6. Use the night.Ambient temperature falls a long way overnight in Britain. Opening a cool box on a cold night to let the contents chill, then closing it before dawn, resets it usefully. The same trick applies to anything you are keeping in the shade.
7. Buy little and often where you can.On a campsite near a shop, buying fresh food daily is easier and safer than keeping three days of it cold. This is how most of the world manages without domestic refrigeration.
8. Handle eggs and dairy sensibly.UK eggs are sold unrefrigerated and keep at cool room temperature — just keep them consistently cool rather than moving them in and out of cold. Hard cheese keeps well wrapped in a cool shaded place; soft cheese does not. UHT milk is the practical answer for anything more than a day or two.
9. Take a thermometer and use the discard rule.If you are keeping chilled high-risk food at all, know its temperature. If it has been above 8°C for a couple of hours in warm conditions, it goes. Improvised cooling makes this judgement more important, not less.

Tips

• A block of ice frozen in a large plastic container lasts far longer than cubes or thin gel packs, and gives you drinking water as it melts.
• Salt in ice water lowers the temperature further and is a good way to chill drinks quickly in a separate bucket, keeping the food box closed.
• Wrap the cool box in a reflective blanket or a light-coloured towel — radiant heat from the sun is a substantial part of what warms it.
• Vacuum flasks work in both directions. A flask chilled with ice water then filled with cold milk keeps it cold for a surprisingly long time.
• If you are relying on a campsite freezer to refreeze ice packs, take two sets so one is always frozen.

Common mistakes

• Relying on evaporative tricks for high-risk chilled food — They lower temperature by a few degrees, not to 8°C. Cooked meats, dairy and prepared salads kept this way are not safe, however clever the arrangement.
• Taking three days of fresh meat and hoping — A cool box is not a fridge. Take the first day fresh, the second frozen, and plan tinned or dried for later.
• Keeping the drinks in the food box — Constant opening for drinks is what kills the cold. Separate them, or keep drinks in a bucket of ice water.
• Leaving the cool box in the sun with a dark cover — Radiant heat is a large part of the load. Shade and a light-coloured cover cost nothing and add hours.

Alternatives

• Well-packed cool box with frozen mass: The only method that genuinely holds chilled food at a safe temperature, and only for a limited time. The mainstay for the first day or two.
• Powered cool box or 12V compressor fridge: A compressor model holds a set temperature properly and is the real solution for caravans and long trips. Thermoelectric coolers only cool relative to ambient and may not reach 8°C in heat.
• Evaporative cooler — damp cloth or pot-in-pot: A few degrees below ambient in dry moving air. Good for butter, vegetables, drinks and general freshness; not a substitute for refrigeration.
• Shaded ground or a shallow pit: Free and surprisingly effective for keeping things a few degrees cooler than a table in the open. Best combined with a breeze.
• Ambient-stable menu: The most reliable option of all: tins, dried goods, UHT milk, hard cheese, cured meat and fresh produce that needs no cooling.

Questions people ask