Colourful Campfires

Everyone knows that you get yellow fire from burning wood, depending on what you add to a fire you can change the colour of its flame. The reason particular colours are given out is due to the energy level the ‘burning’ happens at. Remember the old period table? (or if you had modern enough science teacher; a periodic galaxy?) well its all down its arrangement.

The Sciencey Bit

(Skip this if you really don’t want to know why) The reason different compounds or elements produce different colours when burnt is the oxygen combines with them changing the arrangement of the atoms electrons.

Electrons form orbits or ‘shells’ with higher levels of potential energy for each one in each each orbit, filling up the bottom orbits first. When an electron is exchanged from one shell to another light (photons) must be emitted with an energy matching the change in ‘height’ (potential energy) to maintain balance. The energy of a photon is determined by the Planck constant multiplied by its frequency (E = h×?) which means that different energies result in different frequencies some of which can be seen as a colour.

The Example Bit

The most readily known examples of coloured fire are interstellar stars, although in all honesty they’re not really balls of fire but energy releasing spheres of luminous plasma. Anyway, they come in a variety of different colours depending on there temperature which is based on there dominant fuel, in the The Sun’s case it is 75% Hydrogen and 24% Helium giving it a yellow colour from our atmosphere. As the Sun ages the Hydrogen will become Helium through fusion and it will appear red, just like the the Sun Krypton orbits in Superman and it is called what is known as a Red Dwarf. As the Helium ‘burns’ together into even denser materials it will eventually change to White Dwarf.

Another example that is slightly more down to Earth is the use of different compounds for stunning sky bound effects called fireworks. To produce the most brilliant colours other elements are used to enhance the colour produced from burning, usually Chlorine, which is toxic in large amounts.

The Safety Bit

WARNING: I wouldn’t suggest acquiring any of these elements and trying it out for yourself, especially since some of these substances alone are radioactive, toxic or both! This is intended as a reverse lookup; you see the colour then work out what made it. I’ve not listed every substance just the ones I could find any information on.

The Referencey Bit

Name Metal Image Flame Notes
Lithium
Li   3
Alkaili Lithium suspended in Oil in Test tube by BioNerd Red to White Lithium Flame by Metal Chem White Fume
Strontium
Sr   38
Alkaline Earth Strontium in Radiation Container by BioNerd Red, Crimson Strontium Flame by V31S70 Violent Reaction in Moisture, White Fume
Calcium
Ca   20
Alkaline Earth Calcium in Test tube by BioNerd Brick Red, Orange Calcium Flame by Metal Chem  
Iron
Fe   26
Transition Iron (filings) in Test tube by daynoir Gold Easily Magnetic, Symbol from the Word ‘Ferrum’
Sodium
Na   11
Alkali Silvery White Yellow Sodium Flame by Metal Chem Easily Cut with Knife, Reactive with Water, White Fume
Manganese
Mn   25
Transition Silvery Metallic Yellowish green Poisonous, esp. if inhaled
Molybdenum
Mo   42
Transition Grey Metallic Yellowish green May have facilitated multicellular lifeforms
Barium
Ba   56
Alkali Earth Barium in Radiation Container by BioNerd Pale/Apple Green Barium Flame by Metal Chem Mades rare Gem Benitoite
Boron
B   5
Metalloids (Deep) Brown Bright green Used in Scientific Glassware
Thallium
Tl   81
Poor Silvery White Pure green Highly Toxic
Antimony
Sb   51
Metalloids Antimony in Test tube by BioNerd Pale green antimony Flame by Metal Chem  
Tellurium
Te   52
Metalloids Lustrous Silver Pale Green  
Phosphorus
P   15
Non Dull Red with White Sheen Pale bluish green Reactive when Cut, therefore used in Matches
Zinc
Zn   30
Transition Zinc in Test tube by BioNerd Bluish Green Zinc Flame by Randeeryan White Fume
Arsenic
As   33
Metalloids Arsenic in Test tube by BioNerd Blue Extremely poisonous
Bismuth
Bi   83
Poor Bismuth in Test tube by BioNerd Blue Slightly Radioactive, Very Low Toxicity, Yellow Fume
Caesium
Cs   55
Alkaili Caesium in Radiation Container by BioNerd Blue Slightly Radioactive
Copper
Cu   29
Transition Copper in Test tube by BioNerd Blue Copper Flame by Randeeryan Black Fume
Indium
In   49
Poor Light Grey Blue Used in Liquid Crystal Displays, Toxic
Lead
Pb   82
Post-transition Lead suspended in Oil in Test tube by BioNerd Blue High Density, Toxic, Stops Xrays Easily
Selenium
Se   34
Non Dark Grey with metallic sheen Azure blue Key Ingredient in Head’n’Shoulders, MacGuffin in Evolution
Potassium
K   19
Alkali Metal Silvery White Purple Potassium Flame by everyones idle Highly Reactive with Water
Rubidium
Rb   37
Alkali Grey White Red-violet Rubidium Flame by Metal Chem Highly Reactive with Water OR air
Aluminium
Al   13
Poor Aluminium in Test tube by BioNerd White Common Use, Very High Strength:Weight Ratio
Magnesium
Mg   12
Alkaline Earth Magnesium in Test tube by BioNerd White Magnesium Flame by I. Gelgard White Fume
Titanium
Ti   22
Transition Titanium in Test tube by BioNerd White Food Colourant E171 (Titanium Dioxide)

Photo credits:

Why try something dangerous?

Around 20th September the (Large) Hadron Collider started its first circles, there was speculation in the media, particularly Radio One with Scott Mills (Chris Moyles is off) were they would say that the first signs would be television and radio signals stopping and then cutting all sound! Why? The hype was that a black hole would be formed, suck in the Earth and destroy everything.

I’ve heard a few ask why try something that might cause a disaster? I can only think that you never know what you might discover exploring the unknown, whether its the deepest ocean, the highest peak of the mysteries of the Universe.

Infra-red, Ultraviolet, and X-rays were all discovered by witnessing something unknown and trying to find out why it happened. Infra-red has Communications and Military applications, Ultraviolet protects and entertains and X-rays have medical applications. They are very usual to us and exploring the reason for something unknown eventually allows us to utilise it some way.

So why try something dangerous that you might learn something from; because exploration is fun

Little history on Digital Lighting Effects

Another amazing feat from production teams at Pixar Animation Studios, Emeryville, California, “made possible by modern technology (William*)”. With processors and memory available in such large quantities more computing can be done in less time, with time being money, and films having a limited budget it means higher quality films can be made at lower special effects costs.

Simply put: How?

The film WALL·E uses a derivative of the Ray Tracing Technique, light rays are projected perpendicular to the viewpoint plane into the digital environment and reflected off surfaces until a set number of bounces or they reach a light source. This creates a very realistic looking shot, with the realism being proportional to the number of reflections, 1 bounce casts shadows but doesn’t produce any ambiance, 3 looks only just plausible but will be too dark, 8 would be acceptable for daytime television and a full 16 or more are used in motion pictures.

As you can imagine each bounce has to be remembered, the colour information of its reflecting surface(s) and the distance between each one until it matches a finishing condition, this has to be done for each pixel. A rough idea of film resolution is 2048 by 1152, that’s 2,359,296 light rays (2.4 MegaPixels) every 1/24 of a second. An awful lot to remember for just one frame of 129600 in a 90 minute feature.

Is there a simpler way?

There are many other ways, each with pros and cons, my particular favourite, for sentimental reasons, is Ray Casting, the technique used extensively in the film Tron (1982).

Ray Casting functions in a similar way to Ray tracing except there are no bounces once reaching a surface, colour and shading is faked. With less information to remember the process is a lot quicker but also has more inaccuracies. If the shading and colouring isn’t done proficiently then the entire shot looks fake.

Further Advances

There you have it, the basics in how light and shadows are produced digitally. Mathematical equations work out the path a real light ray might take, complicated stuff made possible by the advances in technology. Luckily Pixar aim to create one frame (1/24 second) to be rendered in 3 minutes, making a whole film take a year, so its safe to say we’re a long way off being able to create photorealistic digital environments in realtime. When that happens I would worry, if we could create a near perfect environment in a simulator and you went into that simulator how would you know if you really left?