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Old Fashioned Ice Cream Makers²
老式冰淇淋机

Have you ever seen an old-fashioned ice cream maker¹? Nestled inside the wooden bucket, there’s a metal canister with a hand crank on top. Cranking the handle scrapes the sweet, creamy mixture from the sides of the metal canister, which sits in a bath of ice water and salt. But what does salt have to do with freezing?
你是否见过冰淇淋机？这种冰淇淋机带有木桶，而木桶内安装了一个顶上带手摇曲柄的金属罐。摇动手柄将糖和奶油的混合物从泡在冰盐水中的金属罐的一边挤出来。但是盐在冰冻过程中有什么作用？

Why not just use plain ice water?
为什么不是只使用淡冰水？

The bath of salty ice water freezes ice cream faster than plain ice water could. And speedy freezing does more than minimize the cranking time on a hot summer’s day. A fast freezing process also yields small crystals, insuring a silky texture³. Slower freezing could make big crystals with an unpleasant crunch⁴, kind of like ice cream that’s gritty with freezer-burn.
盆中的冰盐水能比淡冰水更快的冻结冰淇淋。在炎日的夏天，快速制冷能够最大限度的减少摇动手柄的时间。快速制冷过程也能够产生微小的冰晶，确保丝滑的口感。较慢的制冷过程则形成大的冰晶体，使口感变差，似乎冰激凌表面因为冷冻变硬了。

The coldest that salt less ice water can get is 32 degrees Fahrenheit⁵, where there’s a balance between the rates of melting and freezing. Add salt to the mix and the energy balance tips, allowing the temperature to drop below 32 without freezing.
含有少量盐的冰水温度最低可达华氏32度，这一温度是凝固和融化的平衡点。将盐加到最大量能打破能量平衡，使得温度低于32度而不结冰。

Salty
盐

Let’s say you toss a handful of salt into ice water, and the temperature drops to 20 degrees. At this lower temperature, salty ice water can absorb more heat from the mixture inside the canister, freezing it faster than salt less ice water could. This means you can quit cranking sooner, kick back on the porch and enjoy some good-old-fashioned ice cream.
让我们尝试一下，你将少量盐投放到冰水里，温度降到了20度。在这种低温里，盐水能从金属罐里的混合物中吸收更多的热量，与淡冰水相比能尽快将其冻结。这意味着你能快速停止摇动，返回走廊，享受美味的老式冰淇淋了