White is often considered the absence of color. However, white light is actually made up of all the colors of the visible spectrum. So in theory, you can make white by mixing certain colors together. This article will examine whether it’s possible to create white paint or light by combining other pigments and wavelengths.
How White Light is Made
White light contains all the wavelengths of the visible light spectrum. The visible spectrum includes wavelengths from about 380 to 780 nanometers. Each wavelength corresponds to a different color. When all these wavelengths strike the eye at the same intensity, the eye and brain perceive the combination as white.
So white light is not the absence of color, but rather the balanced blending of all the colors in the visible spectrum. This is known as an additive mixture, where combining wavelengths adds up to white light.
Primary Colors of Light
There are three primary colors of light: red, green, and blue. By mixing different intensities of these three colors, all other colors can be created. This is known as the RGB color model.
Here’s a table showing the main wavelengths for each primary color:
| Color | Wavelength (nm) |
|---|---|
| Red | ~700 |
| Green | ~546 |
| Blue | ~435 |
When red, green, and blue light mix together in equal intensities, they produce white light. This is how televisions, computer screens, and other displays create different colors – by mixing red, green, and blue sub-pixels together in different combinations.
Pigment vs. Light
It’s important to distinguish between the primary colors of light and the primary colors of pigment. Pigments absorb and reflect different wavelengths of light. The primary colors of pigment are cyan, magenta, and yellow.
While televisions use an additive RGB color model, printing uses a subtractive CMYK model. In printing, the inks filter out wavelengths to create colors. Combining cyan, magenta, and yellow pigments creates black, while combining RGB colors creates white light.
So we need to consider pigments and light differently when asking if colors can be mixed to create white.
Mixing Paint Pigments
Unlike with light, you cannot create pure white by mixing common paint pigments together. Pigments selectively absorb certain wavelengths, so mixing them generates darker and murkier colors.
For example, mixing the primary paint pigments cyan, magenta, and yellow produces a dark brown. This is because each pigment absorbs some frequencies and reflects others. Combined together, they absorb more wavelengths than they reflect, resulting in a dark color.
Titanium dioxide is a common white pigment used in paint. It strongly scatters and reflects all visible light wavelengths equally. No combination of cyan, magenta, and yellow can produce this bright white color.
However, some lighter tints can be created by mixing paints. Mixing a small amount of pigment into a large amount of white paint thins out the color. This creates lighter tints while retaining the white base. But no combination of pure chromatic paints can create white.
Mixing Colored Lights
As explained above, combining the primary colors of light – red, green, and blue – at full intensity results in white light. This can be demonstrated using red, green, and blue theater spotlights. When directed at the same spot on a wall or other surface, the eye perceives the combination of the three as white.
Computer displays and TV screens utilize this principle to create colors. Tiny red, green, and blue sub-pixels combine in different proportions to produce millions of colors. Mixing them equally generates white light.
| Ratio | Red | Green | Blue | Resulting Color |
|---|---|---|---|---|
| 1 | 100% | 100% | 100% | White |
| 2 | 100% | 0% | 0% | Red |
| 3 | 0% | 100% | 0% | Green |
| 4 | 0% | 0% | 100% | Blue |
This table demonstrates that mixing full intensities of red, green, and blue light creates white.
Other Ways to Make White Light
Besides combining red, green, and blue sources, there are other ways to produce white light:
– Sunlight appears white because it contains a near-equal mixture of all visible wavelengths. The sun’s surface emits light across the entire visible spectrum.
– Light from incandescent and halogen bulbs has a thermal emission spectrum that peaks in the infrared but contains significant power across the visible wavelengths. This broad spectrum distribution allows the filament to produce a white glow.
– Fluorescent lamps have a phosphor coating that glows white when exposed to ultraviolet radiation. Different phosphor mixtures can tune the shades of white light.
– White LEDs combine a blue LED with a yellow phosphor coating to balance the two colors into a white appearance. Varying the exact hue of yellow yields different color temperatures.
So in summary, combining colors of light can produce white, but the most balanced white light comes from a broad, continuous spectrum source like the sun or a thermal emitter. Discrete color combinations appear white but may not have an evenly distributed power across all visible wavelengths.
Conclusion
While mixing pigments generally yields darker browns and grays, combining different colors of light can produce white. This is because light is additive – the wavelengths from each source get added together. Red, green, and blue are the primary colors of light. Mixing these three colors at full intensity results in white light.
Displays like TVs and computer monitors take advantage of this fact by mixing red, green, and blue sub-pixels to generate a full spectrum of colors. But pigments work differently than light. With pigments, combining colors typically produces darker shades. No mixture of pure chromatic paints can create white – a specially engineered white pigment like titanium dioxide is needed.
So in summary, you can create white light by mixing red, green, and blue sources. But white paint requires specific pigments that strongly scatter all visible wavelengths of light. Understanding the difference between additive and subtractive color mixing explains why we can generate white light but not white paint by combining colors.
