This code was widely used in the 1970s, but is much less used today. (The terms bandana code, hanky code, or flagging are much more widely used among those in the leather subculture than the term handkerchief code.) It should be noted that this code has come into more general usage today.
Generally speaking, solid turns to a liquid at its melting point. Ice turns to water at 0 degrees Celsius. Chocolate melts at 25 degrees Celsius- Yum! Ice (solid) thaws when the temperature rises above 32 degrees Fahrenheit, becoming water (liquid). Other solids (oddly) vary. Generally speaking, solid turns to a liquid at its melting point. Chocolate melts at 25 degrees Celsius- Yum! Ice (solid) thaws when the temperature rises above 32 degrees Fahrenheit, becoming water (liquid).
Background. Boiling Point. A liquid will start to boil when the temperature of the liquid reaches a point where the pressure of the vapor from the liquid equals the pressure of the surrounding air. A liquid placed in vacuum will boil at lower temperatures than in normal conditions.