🕳️ Cellar

A cellar (root cellar, cold cellar) is an underground or half-buried room where food keeps cool. The cold comes from the earth itself: uninsulated masonry walls let the ground temperature pass inside. Most vegetables do well there at 32 to 40 °F (0 to 4 °C) and 80 to 95 percent humidity.

A cellar has its quirks. Warm air rises, so the top runs warmer, which is why people hang thermometers at different heights. A dirt floor holds moisture, while on concrete you put out pans of water. Potatoes first spend 7 to 10 days in a warm, dark place so the skins thicken, then go into the cold at about 38 °F with 85 to 90 percent humidity. Above 40 °F they sprout. Onions and squash want drier air, roughly 55 to 60 percent.

Milk needs nearly the same cold: pasteurized milk keeps at 35 to 40 °F, which is 2 to 4 °C. No wonder farm families looked for cold in the ground and in water. At Hampton in the US, a dairy built between 1790 and 1800 sat on a spring and was dug into a hillside. The water ran through channels into a trough around the floor, and stoneware pails of milk stood in it. Butter was the family's big earner: in 1822 they sold about 4,300 pounds, close to 2 tonnes. The dairy worked until the 1940s.

A ranch in Tallgrass Prairie National Preserve did something similar. Crocks of milk, butter and cheese stood neck-deep in a stone trough of slow, cold spring water. In the early 20th century the springs weakened and the water no longer cooled the food.

Sour cream and urum need the same cold, and wine goes underground as well; see wine cellar and marani. For milk in general, read delivery, storage and sale of milk.