TEMPERATURE
Physically, temperature corresponds to the state of agitation of the particles in a substance. Temperature is measured with a thermometer and can be expressed in three units.
The most common in Europe is degrees Celsius (°C). On this scale, zero represents the freezing point of water, and 100°C represents its boiling point at a constant atmospheric pressure of 1 bar. The United States and some Anglo-Saxon countries still use degrees Fahrenheit (°F). Its scale is more compact than that of degrees Celsius. Thus, 0°C = 32°F and 100°C = 212°F. Finally, the International System of Units (SI) officially recognises the Kelvin as the official unit. Its scale is identical to that of degrees Celsius. Therefore, a difference of 1°C corresponds perfectly to a difference of 1K. However, a temperature of 0K corresponds to absolute zero (-273.15°C). Thus, a temperature of 0°C equals exactly a temperature of 273.15K.
Temperature is an important factor in manufacturing processes as well as in the nature of each component of a movement.
Many manufacturing machines and technologies today can achieve precisions on the order of a thousandth of a millimetre (1mm or 0.000001m). Keeping the temperature as constant as possible allows production means to guarantee this precision over time.
Temperature differences are among the most influential factors in the proper operation and adjustment of watches. The choice of material is generally made for its mechanical and physical properties, and the coefficient of expansion is a crucial factor in watchmaking, particularly for regulating organs. This is why Charles-Edouard Guillaume was awarded the Nobel Prize in Chemistry for the discovery of Invar and Elinvar, elastic and temperature-invariant steel alloys. Precise control and measurement of temperature are important in many artisanal and industrial manufacturing processes. From the most sensitive heat treatments requiring complex and highly accurate thermal measurement systems to the artisan evaluating the tempering temperature by the successive colours that heated steel takes on, the concept of temperature is omnipresent, and it would be impossible to establish an exhaustive list.
