freeze drying

sublimation. The process of snow and ice changing into water vapor in the air without first melting into water.

Women, in cold climates, frequently hang their washings in an upper chamber where they will freeze dry. -Salt Lake City Herald, August 7, 1881.

In The Long Winter, Caroline Ingalls washes clothes and hangs them outside during the calm days after a blizzard, and when they are later brought inside, the clothes are stiff, but they are also completely dry.

When the temperature outside is consistently below freezing, wet clothing either left outside or hung outside on purpose is going to freeze. It may not, however, always freeze dry, so that when brought inside, it will no longer be damp or wet. The process by which freshly-washed clothes dry when hung on a clothesline outside in temperatures below freezing is called sublimation. After the water in the clothes freezes, it passes from its solid state (ice) to its gaseous state (vapor) without going through its liquid state (water). Sublimation occurs more quickly when the relative humidity is low, the sun is shining, barometric pressure is low, and altitude is high.

Evaporation in Winter. The phenomenon of “freezing dry” is familiar to every housewife, as it is to every farmer. In the coldest weather some evaporation is all the time going on. Coarse woolen garments will often freeze dry more quickly than they will dry in a moderately warm room. Freezing expands the woolen texture. Each particle of moisture becomes a flake of snow or ice in the cloth. If this is then exposed to wind, the change of dry air constantly growing damper by contact with the frozen cloth dries it out very rapidly. Sometimes in long-continued cold weather soil exposed to fierce winds dried out so as to kill Winter wheat, the leaves of which are all the time giving off some moisture which the roots must replace or the plant must die. — Oakes (Dakota Territory) Weekly Republican (Friday, January 25, 1889): 7.

Freezing Dry. Thick garments, and even thin ones, are injured by the customary hanging them out in winter to “freeze dry.” The wet fibers, even if but a sixteenth of an inch long, are sufficiently expended in freezing to greatly weaken, if not break them. — Rockford (Illinois) Weekly Gazette (January 17, 1883): 6.

     

freeze drying (TLW 18, 22) – see also Chinook