White color things encompass a wide variety of objects, materials, and substances that contain the color white. Understanding what gives things the white color can provide insight into their composition, properties, and applications.
The Color White
White is the color of light that contains roughly equal amounts of all visible wavelengths in the visible spectrum. It is considered an achromatic color, meaning it has no hue. The perception of white is evoked by the entire spectral composition of light entering the eye, stimulating all three types of color sensitive cone cells in the human eye in nearly equal amounts.
In physics, white is the combination of the colors of the visible light spectrum. Sunlight is perceived as white because it contains all the colors of the rainbow mixed together. Objects appear white when they reflect back most of the light spectrum into the eyes, while absorbing little color. Snow appears white because the ice crystals reflect the sun’s light without absorbing any particular wavelengths.
Pigments that Appear White
While white light contains a balance of all visible wavelengths, pigments that appear white do so by selectively reflecting certain wavelengths while absorbing others. Here are some common white pigments:
| Pigment | Composition |
|---|---|
| Titanium dioxide | TiO2 |
| Zinc oxide | ZnO |
| Lead carbonate | PbCO3 |
Titanium dioxide is one of the most widely used white pigments. It reflects visible light strongly while absorbing ultraviolet radiation. It has a very high refractive index, giving it substantial light scattering ability. This makes it effective as a white colorant in paints, plastics, toothpaste, and paper.
Zinc oxide is another common white pigment, used in paints and cosmetics. It reflects visible and near-infrared light. Lead carbonate (also known as white lead) was historically used as an inexpensive white pigment, but its use has declined due to the toxicity of lead.
White Materials
Many common materials appear white because their chemical structures scatter light effectively. Here are some examples:
| Material | Composition |
|---|---|
| Salt | Sodium chloride (NaCl) |
| Sugar | Sucrose (C12H22O11) |
| Paper | Cellulose fibers |
| Milk | Water, proteins, fats, lactose |
| Snow | Ice crystals |
Salt consists of a crystalline lattice of sodium and chloride ions that reflects light in all directions. Sugar crystals also reflect light effectively to give granulated sugar its white appearance. Paper is made up of a mat of cellulose fibers that scatter light.
Milk gets its white color from the scattering of light by its mixture of water, proteins, fats, and lactose molecules. Snow’s ice crystals have varied shapes and surfaces that reflect and refract light in multiple directions to create its bright white appearance.
White Animals
Some animals exhibit white coloration due either to pigments in their skin, feathers, fur, or shells, or from structural color based on microscopic anatomical features that reflect light.
| Animal | Mechanism |
|---|---|
| Polar bear | Translucent fur and reflective skin |
| White tiger | Lack of red and yellow pigments |
| Arctic fox | Camouflage color change |
| Swan | Feather structure |
| White peacock | Leucistic mutation |
Polar bears’ fur is actually transparent, but it appears white because of the reflection of light off their black skin underneath. White tigers have a double recessive gene that suppresses red and yellow pigments. Arctic foxes and other animals can turn their coat white to camouflage in the snow.
Swans use microscopic feather structures to reflect all wavelengths of light. Rare white peacocks carry a mutation that prevents pigment formation.
White Foods
Many common foods are white due to their composition and structure. Here are some examples:
| Food | Reason for White Color |
|---|---|
| Rice | Starch granules |
| Cauliflower | Lack of pigments |
| Onion | Structural color |
| Coconut | Air pockets in meat |
| Vanilla ice cream | Air bubbles |
Rice grains contain starch granules that reflect light. Cauliflower lacks pigments found in other vegetables. Onions have a crystalline structure that generates white structural color.
Coconut meat contains air pockets that scatter light. Vanilla ice cream’s fat globules and air bubbles reflect light to produce its white color.
White Minerals
Many common white minerals owe their color to their crystalline structure and chemical composition:
| Mineral | Composition |
|---|---|
| Salt | Sodium chloride |
| Quartz | Silicon dioxide |
| Calcite | Calcium carbonate |
| Gypsum | Calcium sulfate |
| Talc | Magnesium silicate |
The crystalline lattice structure of minerals like salt, quartz, calcite, and gypsum reflect light efficiently, causing them to appear white. Talc’s soft magnesium silicate sheets also scatter light to produce a white appearance.
Whiteness Perception
The perception of white is closely tied to brightness. A perfectly reflecting white diffuser appears white but also acts as the strongest conceivable light source. Any deviation from perfect reflection by an object results in a grayer, less bright shade of white.
The context in which an object is viewed also impacts whiteness perception. An object may appear white in one context but not another, depending on the colors surrounding it and the lighting conditions. White is often defined in relation to expectations of normality for a particular object or environment.
The psychological perception of white is also influenced by social and cultural associations. Western cultures associate white with purity, cleanliness, virtue, and innocence. In many Eastern cultures, white is the color of mourning and death. Different color meanings can shape the way people perceive the color white.
Mixing Colors to Make White
There are a few ways to make white by mixing paint pigments or light sources of different colors:
- Mixing red, blue, and green light together in equal proportions produces white light.
- Mixing all colors of light completely produces white light.
- Mixing complementary paint colors like red and green, yellow and purple, or blue and orange also produces white.
- Mixing the three primary paint pigments of red, blue, and yellow together makes white.
This works because when paint pigments are mixed, they selectively absorb certain wavelengths and reflect others. Complementary pigments reflect the wavelengths the other absorbs, so mixing them reflects the full spectrum of visible light for white.
Uses of the White Color
The white color has many applications due to its reflective properties, clean appearance, and aesthetic associations:
- Paints, coatings, paper – Titanium dioxide and zinc oxide create bright white colors.
- Textiles – Bleaching removes natural pigments to whitewash fabrics.
- Foods – Whitening agents like titanium dioxide are added to foods.
- Cosmetics – Pigments like titanium dioxide or zinc oxide provide white color.
- Photography – White balances color reproduction for natural looking photos.
- Lighting – White light supports visibility without changing appearance.
The reflective and scattering properties of white give it visibility and brightness desirable across many applications. White conveys cleanliness in products like clothing or foods. It also carries cultural meanings of purity and innocence that influence its use symbolically.
Conclusion
White color arises in objects, materials, animals, foods, and other items through a variety of mechanisms. White pigments like titanium dioxide selectively reflect certain wavelengths of light. Structural color from microscopic anatomical features, air bubbles, or crystalline structures also produce white through light scattering. Understanding the origins of white color provides insights into chemistry, physics, biology, and human visual perception.