Hot water from tap, thermogram footage. Thermography records the temperature of surfaces by detecting long-wavelength infrared radiation. The colours show variations in temperature. The scale runs from white (warmest), through yellow, orange, red and purple to blue (coldest). A colour-coded temperature scale is at right, ranging from 18 degrees Celsius (dark blue) to 53 degrees Celsius (white). This footage shows the hot water tap being used to run water into a jug at a temperature of over 50 degrees Celsius.