Many people have likely wondered at some point if mixing all the colours of paint or light together will create the colour white. This question gets at the root of how colour works and interacts. While mixing all paint pigments together does produce a dark brown or black colour, combining all wavelengths of light actually forms white light. Understanding the science behind this phenomenon requires looking at some key principles of colour theory and the properties of light versus pigments.
Quick Answers
– Mixing all paint pigments together produces a dark brown or black colour, not white. This is because pigments work by absorbing certain wavelengths of light and reflecting others. When multiple pigments are combined, more wavelengths are absorbed overall, resulting in a dark muddy colour.
– Combining all wavelengths of visible light produces white light. This is because white light contains all the colours of the visible spectrum. Light works additively, so bringing all the spectral colours together reconstitutes white light.
– Pigments use subtractive colour mixing – they subtract wavelengths through absorption. Light uses additive mixing, combining wavelengths to form new hues. This key difference explains why mixing pigments vs. light produces opposite results.
– While mixing all pigments makes a dark colour, mixing a few selected pigments in specific ratios can create a neutral grey or light tone. So not all pigment mixing leads to darker colours.
How Pigments Produce Colour
Pigments are materials that impart colour by selectively absorbing some wavelengths of light and reflecting others. For example, a red pigment absorbs most of the visible spectrum except red light, which it reflects to our eyes. The absorbed light is subtracted, not reflected back to the eye, which is why pigments use subtractive colour mixing.
When multiple pigments are combined together, each absorbs more wavelengths of light. All the absorbed wavelengths are subtracted from white light, leaving less to be reflected. With more subtraction of light, the overall mixture grows darker. Mixing all pigments absorbs nearly all visible light, leaving almost no wavelengths to reflect back, so we see an extremely dark brown or black.
| Pigment Colour | Absorbs Wavelengths |
|---|---|
| Yellow | Violet, blue |
| Magenta | Green |
| Cyan | Red |
As shown in the table, yellow pigment absorbs violet and blue light, magenta pigment absorbs green light, and cyan pigment absorbs red light. When all three are mixed together, almost the entire visible spectrum is absorbed, leaving virtually no light to reflect back to our eyes. So the mixture appears very dark.
The more pigments added, the more wavelengths absorbed, and the darker the mixture becomes. That’s why mixing all paint pigments together produces a dark muddy brown or black rather than white.
Additive Colour Mixing with Light
Light operates according to additive colour mixing. This means individual wavelengths of light are added together to create new hues. The primary colours of light are red, green and blue. Combining these adds up to white light, which contains all the colours of the visible spectrum.
This is because white light itself is made up of the entire continuum of visible wavelengths. Sunlight and emitted light from lightbulbs consists of all the rainbow colours mixed together. Our eyes perceive this combination of wavelengths as white.
So when red, green and blue light mix additively, they reconstitute the full spectrum of white light:
| Colour | Wavelengths |
|---|---|
| Red | ~700 nm |
| Green | ~550 nm |
| Blue | ~450 nm |
The red, green and blue wavelengths span the entire visible spectrum from about 700 nm to 450 nm. Bringing all these wavelengths together recreates white light, just as combining pure pigment primaries theoretically reconstitutes black.
Additive mixing allows more complex hues to be created by varying the intensity of the primary colours. It’s the principle behind colour TVs, computer monitors, and other colour displays that start with red, green and blue light sources.
So while pigments subtract wavelengths through absorption, light adds wavelengths to build colours through addition. This key difference produces opposite mixing results.
Mixing Pigments to Make Lighter Colours
Does this mean it’s impossible to mix pigments to produce light or neutral colours? Not exactly. While combining all pigments theorhetically produces black, in reality imperfection in pigments creates dark browns instead.
Additionally, mixing only 2-3 selected pigments together in specific ratios can create neutral greys, beiges, or lighter tones. For example, mixing small amounts of cyan, magenta and yellow produces various light greys. Certain proportions of magenta and yellow yield light beige. So not all pigment mixing leads to darker colours.
But in general, combining more pigments does increase light absorption and subtraction, trending towards darker tones. Mixing all available pigments would maximize absorption, leaving no visible wavelengths to reflect. Hence, theory predicts this would produce black, even though real pigment imperfections give dark browns.
So while additive light mixing produces white from combining all colours, subtractive pigment mixing trends darker from multiple pigments absorbing more light. This key distinction arises from the different physical properties of light versus pigments.
The Science Behind the Colour Mixing
At the core, the contrasting results of pigment vs. light mixing come down to their underlying physics. Pigments selectively absorb wavelengths using molecular electron transitions and chemical bonds. Light in essence consists of electromagnetic waves and photons.
When light shines on a pigment, the pigment’s chemical structure absorbs photons of certain wavelengths by transferring the energy into electron orbital transitions. The pigment reflects unaffected wavelengths back to the eye.
But light mixing involves no chemical absorptions or subtractions. Rather, rays of light with different wavelengths simply superimpose and propagate together. This preserves the intensity of each wavelength, producing additive mixing.
So while pigment mixing relies on selective absorption and reflection of wavelengths using chemical properties, light mixing is a direct superposition of electromagnetic waves that preserves intensities. This key difference in mechanism creates the opposing mixing outcomes.
Applications and Practical Use
Understanding the additive mixing of light and subtractive mixing of pigments has important applications and practical use:
– Display and camera technologies utilize red, green and blue light sources to construct all other hues through additive mixing. This enables complex colour graphics and photography.
– Painters create darker tones by adding black or complementary pigment colours. Lighter tints come from adding white or reducing pigment content. Subtractive colour principles are essential to pigment-based arts.
– The fact that pigment mixtures darken informed historical paint practices. Renaissance painters built up shadows by gradually mixing in more pigments.
– Printers use cyan, magenta, yellow and black ink because these absorb the full spectrum. Combining these pigments can theoretically produce black, though imperfection results in dark brown in practice.
So the physics of light and pigment colour mixing not only satisfies intellectual curiosity but also enables widespread colour technologies, arts, graphics, photography and printing. Understanding additive and subtractive colour proves profoundly useful.
Conclusion
In summary, combining all colours of light additively produces white, while mixing all pigments together subtractively trends towards black. This stems from the different properties of light waves versus chemical pigment absorptions. While counterintuitive, the true physics and chemistry confirms that the colour mixing mechanisms of light versus pigments will produce opposite results. Grasping this key distinction provides fundamental insight into the science of colour and underpins many important practical applications.
