Temper colors on bare, clean, bright steel provide a useful visual method of estimating time and temperature of exposure of heat-affected areas in weldments, judging from surface appearance. When a weld is made by localized heating, temper colors ranging from shades of black, through blue, red, brown and tan will run in bands parallel to the long axis of the weld after the weld has cooled. These variations in color are the effect of various thicknesses of oxide films that form on the surface of iron and steel when heated in air. Sand blasting or pickling can be used to prepare a surface on which temper colors from welding can be observed. Temper colors can give a rough indication of the maximum temperature imposed on the base metal at varying distances from the weld. For example, if two different welds are compared for temper colors, and the brown-purple transition is found closer to the edge of the weld in the first plate, it can be concluded that the weld in the first plate was heated more rapidly and cooled faster than the weld in the second plate. The colors formed on iron and carbon steel by progressively higher temperatures are listed in Table T-2.