Furnace Temperature Colors

[goldsilverpro]

APPROXIMATE FURNACE TEMPERATURE COLORS

Lowest red visible in the dark.......... 470 C ..... 878 F
Dark red, blood-red....................... 550 C ..... 1022 F
Dark cherry.................................. 625 C ..... 1127 F
Cherry-red, full cherry................... 700 C ..... 1292 F
Light red....................................... 850 C ..... 1530 F
Orange......................................... 900 C ..... 1652 F
Light orange.................................. 950 C ..... 1742 F
Yellow........................................... 1000 C ... 1832 F
Light yellow................................... 1050 C ... 1922 F
White.................................... 1150-1200 C ... 2102-2192 F

 

[mwren]

Are these temps for flames inside the furnaces or for the flames that shoot out of the top?

 

[goldsilverpro]

I took them out of an old fire assay book. I'm sure they apply to the chamber of the furnace and the refractory although they could apply to any heated object - the tip of a cigarette, e.g. I would doubt if the flame colors would be reliable, since various flame compositions produce different colors.

 

[Naitsabes]

With all due respect a Slight clarification.

Every temperature has a particular spectrum so yes the numbers are reliable.

Color blindness excepted.

Unless of course there is a dopant that oxidizes and gives off a particular color as in pyrotechnics. Things burn in different colors according to their composition.

But everything material "glows" at a particular "color" related to its temperature be it one degree K or 1,000,000K

 

[FrugalRefiner]

Judging temperature by color is very subjective. The colors we perceive are affected by the surrounding lighting conditions. The first visible redness can be seen at lower temperatures in the dark than in sunlight, as shown on the chart.

I believe our perceptions are also affected by our personal experiences. If the brightest glow you've ever seen is red hot, it's hard to judge the shades of oranges, yellows, and whites. If you've seen the flash of an arc welder, you know what dazzling white means.

I combined the information from about a dozen different sources to create my chart, so most of the ranges overlap due to different terminology and temperatures among the sources.

I included the melting points of a few metals of interest.

The colors you see on your computer screen or those produced by your printer may be different than mine. I provide no warranty as to its accuracy. I've included a pdf file for those who would like a printed copy.

DaveView attachment Heat Colors.pdf

 

[FrugalRefiner]

The moderators would like to thank all of the members that contributed to the original thread upon which this thread was based, as well as those that asked questions showing what was missing. Because of the extra length and interest in this thread we have created the above consolidated version making for an easier read. We encourage all members to read, comment, and ask questions in the original thread, Furnace Temperature Colors.

The Library threads should not be considered to constitute a complete education. Instead, they're more like reading a single book on the subject of recovery and refining. There is so much more information on the forum, and it is impossible to include it all in these condensed threads. Members are strongly encouraged to read the rest of the forum to round out their education.

For those who prefer a printed copy, a pdf file of this thread is provided below.