The History of the Fridge

How did ice houses refrigerate food in one of the hottest deserts on earth?

The Dasht-e Lut Desert in Persia, modern-day Iran, is one of the hottest and driest places in the world. Surface temperatures are known to reach 70 degrees Celsius. It would seem an unlikely place for the invention of the fridge, but this is where it really happened, in 400 BC.

The first fridges were unlike our modern-day appliances, which hum quietly and fit snugly under the countertop. This was a yakhchāl —a large conical structure that rose to about twenty metres high. But how did it work without electricity or a cold climate?

A long, shallow pool fed by canals was shielded from the heat of the sun by a towering shade wall. It was here that ice was made overnight in winter. Before dawn, the ice was harvested and transferred to the pit inside the yakhchāl, where it was covered with an insulating layer of straw. The stock of ice was built up over the colder months, while the building’s unique design helped it last through summer.

The thick walls were made from a special mortar called sarooj to keep the heat out and the cold in. Sand, limestone, and clay were mixed with some more unusual ingredients, including egg whites, goat hair, and ash. The result was highly water-resistant and an excellent insulator.

Inside the yakhchāl, the temperature was kept low by heat transference. Warm air rose, escaping through the hole at the top of the pointed ceiling, leaving a glacial chill in its wake.

Simple. But incredibly effective.

Bronze Age Fridges

People in the Orkney Islands had a more humble cold storage system than the vast yakhchāls in Persia. They would dig a rectangular pit into the floor of their homes and line it with stone slabs. As moisture slowly evaporated through the porous stones, it combined with the cooler ground temperatures to preserve the food.

Now, here’s the clever bit. The prehistoric people had an open gully running through their home, and a tiny rivulet of water diverted from a local stream flowed through the middle of the room. Two open windows – one on the north wall, the other on the east – created a cross draught. The combination of evaporating water and the constant breeze, together with the insulating effect of the sunken floor, maintained the temperature at a few degrees above freezing—perfect for preserving milk, butter, and cheese, even in the height of summer.

The Birth of Birdseye

An American fur trader named Clarence Birdseye visited Labrador, Canada, in 1912. He and some local Inuits were by a hole in the ice, fishing lines dangling into the water below. All of a sudden, one of the lines jerked. The fisherman leapt into action, hauling his line out of the water. On the end of the hook was a fish. For a split second, it thrashed about in the sub-zero air temperature before hanging inertly. The fisherman held his catch out to Birdseye to examine. Remarkably, the fish was already completely frozen. It must have happened instantaneously, almost as soon as it broke the water’s surface.

That evening, Birdseye’s astonishment turned to delight. He thawed the fish and cooked it over a campfire. When he tasted it, it was like no frozen fish he had ever eaten before. At that time, the usual method for freezing meat or fish was to leave it resting on ice for an extended period. In the process, large ice crystals formed, which damaged the cell walls of the flesh and ruined the taste.

But the flash-frozen fish of the Inuits was delicious. Birdseye used what he learnt to establish one of the world’s most famous frozen food brands.

Fishfingers, anyone?

How did cooling technology help a US President who was shot?

On July 2nd, 1881, James A. Garfield, the 20th President of the United States, was waiting in a Washington railroad station when he was shot twice in the back. Bleeding and screaming in pain, Garfield was carried back to the White House, where his injuries were assessed. One of the bullets had done minor damage, but the other was lodged deep in his abdomen, close to his pancreas. Doctors feared he wouldn't last the night.

In the morning, Garfield was still alive but suffering from a fever. One of the doctors remembered reading about a device that lowered the temperature in Yellow Fever wards. He wondered if something similar could be rigged up in the president's sick room.

Navy engineers were called in and presented with the challenge. They constructed a rudimentary air conditioning system. It worked by blowing hot air across cloths soaked in melted ice water. As the water evaporated, it lowered the room's temperature by an astonishing 11 degrees Celsius. The cooling machine helped keep President Garfield comfortable, but it wasn’t enough to save him. He eventually died from his injuries on September 19th, 1881