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).
Heat is probably the easiest energy you can use to change your physical state. The atoms in a liquid have more energy than the atoms in a solid. There is a special temperature for every substance called the melting point. When a solid reaches the temperature of its melting point, it can become a liquid. For water, the temperature needs to be a little over zero degrees Celsius (0oC) for you to melt. If you were salt, sugar, or rock, your melting point is higher than that of water.