Steel Heat Color Chart Calculator
Identify steel temperature by its glowing color.
Reference chart for blacksmiths with forging and heat treating guidance.
When steel is heated, it emits visible light that changes color with temperature. Experienced blacksmiths use this color as a real-time thermometer. This skill — reading heat color — is one of the most fundamental abilities in smithing.
Steel Heat Color Chart
| Color | Temperature (°F) | Temperature (°C) | Use |
|---|---|---|---|
| Black heat | 400–500 | 204–260 | Too cold to work. Risk of cracking high-carbon steel |
| Faint red (barely visible) | 900 | 482 | Minimum for gentle bending of mild steel |
| Dark red / Blood red | 1,050 | 566 | Stress relieving, gentle bending |
| Dark cherry red | 1,175 | 635 | Annealing range for many steels |
| Cherry red | 1,375 | 746 | Light forging, normalizing |
| Bright cherry red | 1,500 | 816 | Good forging heat for high-carbon steel |
| Dark orange | 1,600 | 871 | Active forging range |
| Orange | 1,725 | 941 | Good general forging heat |
| Light orange | 1,825 | 996 | Heavy forging, upsetting |
| Yellow | 1,975 | 1,080 | Near top of forging range |
| Light yellow | 2,100 | 1,149 | Forge welding range begins |
| White | 2,300+ | 1,260+ | Maximum forge welding heat — danger of burning |
Important: Ambient Light Affects Color Perception
Heat colors are best judged in subdued lighting. In bright sunlight, steel that appears black may actually be at dark red heat (~1,050°F). Many blacksmiths keep their forging area dimly lit specifically so they can read the steel accurately.
Worked Example — Identifying Forging Readiness
You pull a piece of 1084 steel from the forge. It glows a consistent bright orange color. Consulting the chart, bright orange corresponds to approximately 1,725°F (941°C). The forging range for 1084 steel is 1,500–2,000°F. At 1,725°F you are well within the safe working zone with a 275°F buffer before the upper limit. You can confidently draw out, upset, or fuller the steel at this heat.
Temper Colors (Low Temperature Oxide Films)
After hardening, blades are tempered at low temperatures. The thin oxide layer on polished steel produces colors:
| Oxide Color | Temperature (°F) | Temperature (°C) | Use |
|---|---|---|---|
| Pale straw | 430 | 221 | Razors, engraving tools |
| Straw | 460 | 238 | Drill bits, taps |
| Dark straw | 480 | 249 | Punches, dies |
| Bronze / Brown | 500 | 260 | Axes, chisels, knife blades |
| Purple | 530 | 277 | Springs, swords |
| Blue | 570 | 299 | Screwdrivers, springs |
| Light blue | 610 | 321 | Too soft for most tools |
These temper colors only appear on clean, polished steel. Scale or oxidation will hide them.