What Is The Hottest Color Of Fire? How Hot is Blue Flame?

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If you ask a child to draw fire or an adult to describe it, you’ll probably end up with a picture of orange, yellow, and red flames. But, in fact, fire can span the entire spectrum of visible light and while most of us associate fire with yellows and reds, when we turn on a gas stove, the flame is blue with just a hint of orange.

Violet is the hottest color fire. It can burn at around 3,000 degrees Fahrenheit (1,650 degrees Celsius). That’s hot enough to burn almost any material and a violet flame is often seen in welding and cutting operations for this reason.

But that isn’t the only fire that can reach these higher temperatures. So, let’s take a look at flames and their colors in more detail. 

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Also read: Is Fire Alive? Properties and Stages of Fire and Flames

What Is It That Makes Flames Of Different Colors?

hottest color fire

The colors of flame are determined primarily by the heat of the flame as this affects the wavelength of the electromagnetic radiation (light) that is produced.

However, the color may also be influenced by what is being burned (such as copper producing a greenish tint to flames) and by how well the substance is being burned.

That latter point is very important, it’s why when burning a single gas, for example, using a welding torch that you find yourself confronted by two cones of flame of varying color. 

The hottest part of the flame is where the substance is being completely consumed (or as close to complete as possible) in conjunction with the oxygen it is burning in, whereas the reaction is much less efficient in the coolest part of the flame. 

What Colors Can Be Found In Fires?

All colors of the spectrum can be found in flames, in fact, this includes the parts of the spectrum that are not, typically, visible to the human eye and they can include:

  • Infra-red
  • Red
  • Orange
  • Yellow
  • Green 
  • Blue
  • Indigo
  • White
  • Violet
  • Ultra-violet

In the main, the color of a fire is a good indicator of the temperature of that fire, but not always as we shall see in a few minutes. 

Also read: Does Fire Have Mass? What Does It Weigh?

Which Color Represents The Hottest Fire?

The hottest color flames include; violet, ultra-violet, indigo, and some blue flames, as they can all reach up to 3000 degrees Fahrenheit (1650 Celsius).

Also read: Does Fire Kill Germs/Bacteria/Viruses?

How Hot Is Red Fire?

Red fires are the coolest of fires. This helps to explain why most of us associate reds, yellows, and oranges with the color of fire – cooler fires are more common in nature than hotter ones. 

A red flame, typically, gets to a maximum of about 800 degrees Celsius, that’s about 1470 degrees Fahrenheit. While it may not be the hottest fire it can easily melt glass, tin, zinc, and more. 

Also read: How Hot Is A Lighter Flame?

How Hot Is Orange Fire?

Orange flames are hotter than red flames and they can easily be made by burning common items, there’s no need to delve deep into your chemistry set for them. 

An orange fire can produce a maximum of around 1100 degrees Celsius and 2,000 degrees Fahrenheit, this flame is hot enough to melt gold and copper and the “Bronze Age” came into being when mankind first learned to consistently produce an orange flame. 

How Hot Is Yellow Fire?

A yellow flame is not a lot hotter than an orange flame and it only ekes out an extra 100 degrees Celsius or so to provide a 1200 degrees Celsius or 2,220 degrees Fahrenheit maximum heat. 

This adds a little flexibility to the metal worker’s armory but doesn’t drastically change what can be done with the flame. 

How Hot Is Green Fire?

As we warned about earlier, not all colors relate to the heat of a flame. And green is the color that you have to watch out for because a green fire only indicates the chemical(s) that is(are) being burned (which is most commonly, copper).

You can’t gain any information about the heat of the flame from this color and that means you should be very, very careful around a green flame as the temperature could be drastically higher than you might have expected it to be. 

How Hot Is Blue Fire?

Blue fires can get quite a bit hotter than yellow fires and they can range between 1400 degrees Celsius (2,550 Fahrenheit) and 1,650 degrees (3,000 Fahrenheit)!

Welcome to the Iron Age. Once humans learned to make and control blue fires, they began to be able to melt brown iron ores and extract iron. 

How Hot Is Indigo Fire?

An Indigo flame burns at the top end of the Blue fire range at 1,650 degrees Celsius and 3,000 degrees Fahrenheit respectively.

However, it’s easier to control the heat output from an Indigo flame than a blue one, due to the smaller temperature range and heat output. 

That makes Ironworking easier too and the production of glass because sand melts at just 100 degrees below the temperature of the Indigo Fire. 

How Hot Is White Fire?

White fires, as we’ve already noted, are the hottest fires completely in the visible spectrum and they can burn as high as 1,500 degrees Celsius (Blue and Indigo will contain some part of the ultra-violet spectrum as will Violet itself) or 2730 degrees Fahrenheit.

When people talk of things being “white hot” it’s because white flames are super-hot and they can easily burn through Cobalt, Nickel, and even the radioactive material Uranium.  You really don’t want to be on the receiving end of a white flame. 

How Hot Is Violet Fire?

Violet fire is the hottest of them all and our ability to use violet fire in industrial methods means that we are able to work with cast iron and steel, as well as creating the hardest porcelain and melting the toughest of metals – titanium

A Violet flame burns at temperatures above 1,650 degrees Celsius and 3,000 Fahrenheit and you won’t be able to make a hotter flame. 

What Chemicals Can Produce Different Colored Flames?

You still need to be cautious when it comes to using the color of a flame to gauge its temperature. That’s because impurities and other chemicals can cause a colored element of a flame that you might not have been expecting. 

If this is the case, the physical appearance of a fire may be either be exaggerating or underestimating the heat that it puts out considerably. 

Some examples of typical reactions that cause specific flame colors are listed here, however, we must stress – this is not an exhaustive list. 

  • Strontium chloride/nitrate – can turn a flame red.
  • Carbon and/or calcium chloride – can turn a flame orange. This is a very common reaction when you’re making a fire outdoors for cooking or for warmth.
  • Sodium chloride (table salt), sodium carbonate and borax – can all turn flames yellow.
  • Copper and/or barium – may turn a flame green (and remember green flames never have a link to the temperature of the flame)
  • Copper chloride and totally consumed carbon – can result in a blue flame. 
  • Indium – results in Indigo flames.
  • Magnesium and magnesium sulfate – can both lead to a bright white flame.
  • Potassium nitrate AND potassium sulfate together – burn with a violet flame.

You can see a variety of flames colors and how they are made here:

What Is The Color Of Fire?

Despite all of the different colors that fire can be, there’s no doubt that for human beings the color of fire remains orange/red/yellow. 

But why is that? After all, we’ve known that fire can burn in different colors for tens of thousands of years (possibly much longer), surely our definition should have changed by now?

Well, it turns out that the vast majority of things human beings burn, tend to contain a whole lot of carbon. That is wood, paper, coke, charcoal, coal, oil, etc.

And as we’ve just seen, unless carbon burns completely, it produces an orange flame. 

Once all the carbon has been consumed in the fire reaction, then the flame will often change color as the remaining fuels burn hotter than the carbon does. 

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