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While working on my Demon Prince for the 2003 Chicago Golden Demon I had several e-mail conversations with Jeff Freeman - another Golden Demon-winning painter in the San Francisco Bay Area – who happens to have studied combustion for one of his Masters degrees. We were trying to determine why fire looks the way it does. In writing this tutorial I’ve drawn heavily on those talks and also on this excellent article on the color of fire. I want to thank Jeff for his insights and for helping me quantify my own feelings on the matter.

So, let’s start at the beginning… What is fire? Fire is the visual result of combustion. When something burns part of the energy released is converted into light. This light is what we see as fire. Sounds pretty simple, huh?

Unfortunately pure combustion is hard to acheive, so fire is rarely a pure color.

A STRATA OF LIGHT

When you look at a fire you're seeing the energy spew out from the combustion source – the bottom of the fire. Ideally fire would burn bluish-white at the source (the hottest part of the flame). However this blue light is usually lost in the tongues of orange flame shooting up from the fire.

Created by hot carbon soot trailing off the fire, these flames cool as they burn, making the whitish-yellow to dark orange range of light we're accustomed to seeing in a fire. This strata of light has levels of heat and color, going from brightest at the base to darkest at the top of the flames. For this reason painting fire from red at the bottom to yellow at the top is wrong. Fire burns brightest at the source, not the extremities!

Also, because the flames form such a larger area than the blue combustion zone, they overshadow its light. It's generally not a good idea to paint a fire with a blue base for this reason. (Coupled with the fact that, due to the limitations of paint as a medium, whitish-blue looks funny to the viewer’s eye at the base of a fire. In addition, when layered or blended with yellow, blue paint may look green).

Let's use the example of a campfire to illustrate this strata of fire:

RIGHT

Combustion occurs at the base of the flames, where the wood is actively burning. The tips are the 'coldest' parts of the flames.

WRONG

Here combustion occurs at the tips of the flames, where there is no material to burn. This color scheme places the coldest part at the base, where combustion normally occurs.

Convection is the other reason why fire has this distinctive yellow/orange strata. If you look at the article I referenced at the beginning of this tutorial, fire in zero gee forms a perfect blue halo of light around a candle flame, but when put into gravity, the convection of the heat rising causes it to have these stereotypic layers of color:

This convection is what draws out the tongues of flame – the hotter flames and sparks rise up, creating a vacuum effect which draws cooler air into the base of the fire, continuing the combustion cycle.

I'm not sure why mini-painters started painting fire the wrong way... I guess they were mimicking the shading on other parts of the mini: the lightest areas of a surface are at the top and darkest at the bottom. However, painted highlights like this are the result of an implied light source (the sun, etc.) coming from above the mini.

While this normally works great for a solid object, like a cloak or an arm, fire is a light source itself and thus doesn’t appear like a solid object being lit from above. If anything, it should be lighting other surfaces around it (the painting style popularized lately as ‘source lighting’).

THE COLORS OF FLAME

Another issue with painting fire realistically is the use of color. Fire is an energy effect. It dissipates when the combustibles are exhausted. Because of this glowing combustion, colors ranging from whitish yellow to dark orange are primarily what you’ll see in a natural fire (I am excluding chemical fires for the scope of this tutorial).

Fires do not become dark red or black as they cool. As the flames rise and lose their heat, they become a darker orange, but never as dark as a molten or superheated material (like iron or lava) does when it cools:

Solid materials which have been heated to glowing red will typically cool down through a dark orange, red and black stage as they eventually return to a solid state. But not so fire. Fire will become dark orange (at most), before disappearing as all the energy is used up.

The only exception to this is a type of fire that burns a lot of solid material, such as an oil fire. Fires like these produce a lot more carbon particles, which in turn leave the top of the flames as smoke – a dark grey to black mass. The extra material in the flames is what makes these fires appear darker at the tips, not the flames themselves cooling to that color:

If you’re depicting an oily fire like this (or the miniature is sculpted with a smoky appearance, such as the Rackham fire elemental), then this approach would work.

LIGHT TIPS, DARK FLAMES?

Okay then, you ask – why is it that flames sometimes look like the hottest part is at the tips, and not the bottom? Well, after much scratching of heads, and observation, I have to say it’s due to convection and the combustion process.

1. The convection vacuum effect draws up tongues of hotter material from the base of the fire.

2. Since the center of a fire is an oxygen-poor region the fuel cannot burn completely within the bottom of the fire. Sometimes as the flames rise, the combustibles are finally given the air they need to fully react, thus sparking these brighter tips. In effect, you get micro-eruptions of heat and light from a slightly 'darker' backdrop of flame.

Here's an example of this effect from some paper I burned to observe flames:

These tips of flame will appear briefly brighter than the strata they’re coming out of, at least until they use up their energy and dissipate. Convection will bring up more and the cycle will continue.

PUTTING IT ALL TOGETHER

Okay, so we’ve got flames that sometimes get brighter at the tips, don’t become red, and still turn from yellow at the base to dark orange at the top. How does all that work with the idea of strata?

Well… since by design minis must be sculpted with solid 3D flames, we have to idealize the fire effects we paint on them to approximate the characteristics of the real thing as closely as possible. For practical purposes this means having the strata of color from lightest to darkest, with each level having it’s own flame-tips going from darker to lighter as you proceed up the flame:

As you see here, I painted each level of the flames slightly darker as I went up the column. I began with yellow-white at the bottom and went to a reddish-orange at the top.

For each level the tips were painted slightly lighter than their corresponding layer – yellow flame had white tips, orange had yellow tips, and dark orange had orange tips. To make it appear less stylized, though, I added some brighter tips to the darkest levels, to mimic the convection effect. Hopefully this helped approximate the real thing!

Now let's see this effect done step by step on a mini.

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All images and text Copyright 2004 Laszlo Jakusovszky