When temperatures rise, many people instinctively reach for a white shirt, while dark clothing remains in the closet. This practice relates to how colors interact with light and heat from the sun. Understanding these principles explains why white garments offer more comfort on a hot day, while black ones tend to increase warmth.
The Science of Light and Heat
Light is a form of electromagnetic radiation, and it carries energy. This energy, originating from sources like the sun, can interact with objects in several ways: it can be absorbed, reflected, or transmitted. When light energy is absorbed by a material, it is converted into thermal energy, which we perceive as heat.
Different materials and colors interact with this radiant energy distinctly. An object’s color is determined by the wavelengths of visible light it reflects, while absorbing others. For example, a red object reflects red wavelengths and absorbs most other colors. This interaction is not limited to visible light; materials also absorb or reflect non-visible electromagnetic radiation, including infrared, which is a significant component of solar heat.
Why White Keeps You Cooler
White surfaces appear white because they reflect nearly all wavelengths across the visible light spectrum. This high reflectivity extends beyond visible light to a significant portion of infrared (heat) radiation. When white fabric reflects light, the energy from that light is not converted into heat within the material. This minimizes the amount of thermal energy transferred to the fabric and, subsequently, to the wearer’s body.
This property makes white an effective choice for managing heat, helping to maintain a cooler body temperature. White fabrics can reflect a large percentage of sunlight, sometimes absorbing as little as 10-20% of solar radiation.
Why Black Makes You Hotter
In contrast, black surfaces absorb most wavelengths of visible light. This extensive absorption also applies to a significant portion of infrared radiation. When light is absorbed, its energy is converted into heat, leading to a noticeable increase in the material’s temperature.
This conversion means that black clothing accumulates more heat from solar radiation compared to lighter colors. The absorbed heat is then transferred to the wearer’s body, contributing to a feeling of increased warmth. For instance, black T-shirts can reach surface temperatures 5 to 10 degrees Celsius higher than white T-shirts under direct sunlight.