Note 22 — Chapter XIV · —MEASURING MACHINES, TOOLS, AND DEVICES. (continued 2)
Reading edition
The temperature may be judged by color; at 500° F. iron has a blackish appearance; at 575° it is blue; at 775° red in the dark; at 1,500° cherry red, and so on, getting lighter in color, until it becomes white, or fit for welding, at about 3,000°.