The choice between hot water dough (tang mian, 烫面) and cold water dough (leng shui mian, 冷水面) is the fundamental fork in Chinese dough preparation — determining the texture, translucency, and stretchability of the resulting wrapper or noodle. The difference is caused by the gelatinization of starch: hot water (above 65C) gelatinizes the starch molecules in the flour, disrupting their crystalline structure and making them more pliable, translucent, and tender; cold water leaves the starch in its natural crystalline state, producing a firmer, more elastic dough that becomes slightly chewy and opaque when cooked.
Hot water dough (tang mian): Temperature: just-boiled water. Proportion: approximately 1:0.5 (flour:water by weight). Results: pliable, translucent when thin, tender texture, slightly sweet. Applications: potsticker wrappers (for a softer skin), xiao long bao wrappers (Shanghai soup dumplings), har gow wrappers (wheat starch version), spring roll wrappers, scallion pancakes. The dough is easier to roll very thin without tearing. Cold water dough (leng shui mian): Temperature: cold water. Proportion: approximately 1:0.5. Results: firm, slightly elastic, chewy when cooked, opaque. Applications: jiaozi (northern boiled dumplings), wonton wrappers, fresh egg noodles, hand-pulled noodles. The chewiness is valued as an essential textural quality. Warmed water dough (wen shui mian): Warm (40-50C) water — a compromise between the two, used for some pan-fried dumplings and certain flatbreads where moderate pliability is required without the full translucency of hot-water dough.
Irene Kuo, The Key to Chinese Cooking (1977); Eileen Yin-Fei Lo, Mastering the Art of Chinese Cooking (2009)