|MadSci Network: Science History|
How can you make ice without electricity or without a fridge?
How was ice made in the past century, when there wasn't electricity? What chemical were used? and how they kept it cold?
No chemicals were used to make ice before electrical refrigeration was invented, any more than chemicals are used to make ice now: the freezing of water is a physical change, brought about by lowering its temperature. But before refrigerators, one had to use other methods.
The simplest method was to go where there was ice and bring it back. Kings in India (and probably elsewhere) used to have snow brought to them from the mountains, as a delicacy. This is bringing ice from "elsewhere in space."
One could also bring ice from "elsewhere in time." In places where winter temperatures are routinely below freezing, ice was cut from ponds and lakes, then stored in special insulated buildings until needed. In America, the Shakers were well-known for their excellent ice-houses; these were double-walled and triple-roofed, with sawdust packed between, and more sawdust laid thickly on the floor.
Finally, one could use a little ingenuity. The Romans used to make ice in the deserts of North Africa or Palestine by taking advantage of the low humidity (and therefore the low temperatures at night). They would put what they wanted to freeze in a pit well-insulated with straw. The pit would be covered with highly-polished shields or other objects during the day, to reflect the heat of the sun; at night, the pit would be uncovered so that it could lose heat to the desert air.
The same principle was used, for example, in British India. In times and places when the nights were cold, water would be poured into molds at dusk and allowed to freeze; then, at about 3 or 4 AM, the ice would be chipped out of the molds and rushed to an ice-house.
My source is Reay Tannahill's Food in History.
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