Forge & Temper Steel Color Chart
Enter a target temperature to see the matching reference color, for either forging/hardening heat or tempering heat.
Forging / hardening color
Look for: Cherry red
(1498–1598°F / 814–870°C)
Tempering color
Nearest reference color: Dark straw (439°F / 226°C)
Traditionally used for: Scribers, planer blades
Full forging/hardening color chart
Chapman's Workshop Technology (1972), via Wikipedia.
| Color | °F | °C |
|---|---|---|
| Black red (barely visible, only in dim light) | 799–1100 | 426–593 |
| Very dark red | 1100–1299 | 593–704 |
| Dark red | 1300–1497 | 704–814 |
| Cherry red | 1498–1598 | 814–870 |
| Light cherry red | 1599–1798 | 871–981 |
| Orange | 1799–1998 | 982–1092 |
| Yellow | 1999–2296 | 1093–1258 |
| Yellow white | 2297–2397 | 1258–1314 |
| White | 2397–Infinity | 1314–Infinity |
Full tempering color chart
Wikipedia, "Tempering (metallurgy)".
| Color | °F | °C | Traditionally used for |
|---|---|---|---|
| Faint yellow | 349 | 176 | Gravers, razors, scrapers |
| Light straw | 401 | 205 | Rock drills, reamers, metal-cutting saws |
| Dark straw | 439 | 226 | Scribers, planer blades |
| Brown | 500 | 260 | Taps, dies, drill bits, hammers, cold chisels |
| Purple | 540 | 282 | Surgical tools, punches, stone-carving tools |
| Dark blue | 590 | 310 | Screwdrivers, wrenches |
| Light blue | 639 | 337 | Springs, wood-cutting saws |
| Grey-blue | 700 | 371 | Structural steel |
Ready to harden a blade? Check the heat-treat schedule lookup for your steel first.
Frequently asked questions
- What's the difference between forging colors and tempering colors?
- Forging/hardening colors are the glow of steel heated to a high temperature (roughly 800-2,700°F), used to judge forging and hardening (austenitizing) heat. Tempering colors are the thin oxide film that forms on a polished, already-hardened blade reheated to a much lower temperature (roughly 350-700°F), used to judge temper heat. They are two different physical effects at two very different temperature ranges — don't read one chart while trying to hit the other.
- Where does this data come from?
- The forging/hardening color chart is Chapman's Workshop Technology (1972), via Wikipedia's "Red heat" article, which also documents a second historical table (Stirling Consolidated Boiler Co., 1905) with broadly similar but not identical values — expected, since color judgment is inherently somewhat subjective. This tool implements only the Chapman table so it doesn't show two conflicting answers for the same lookup. The tempering color chart is from Wikipedia's "Tempering (metallurgy)" article.
- How accurate is judging temperature by color?
- Not very, compared to instruments. Forging colors depend heavily on ambient light (the same steel looks a different color in bright daylight vs. a dim shop) and on individual eyesight — and the forging chart's bands are roughly 100-300°F wide, far coarser than the precision actually needed to hit an austenitizing target, so use it to judge forging heat, not hardening heat. Tempering colors depend on TIME as well as temperature: steel held at a given oven setting long enough will keep darkening past the color that setting "should" produce, so a long two-hour temper can end up a noticeably later color than a quick one at the same temperature. A pyrometer, thermocouple, or calibrated oven/kiln is far more accurate for both.
- Is my data uploaded anywhere?
- No. Everything runs in your browser — nothing you enter is sent to a server.