Light and materials are inseparably connected, indeed they actually determine each other: neither is visible to the human eye until the two come together. For this reason, great architects have always also allowed themselves to be directed by the light in the choice of their building materials. They use light to draw out contrasts between different materials and they use materials that allow them to create a very specific distribution of light in a room.
Light and materials are mutually dependent on each other. Materials are key to understanding light in architecture because they directly affect the quantity and the quality of the light. Two qualities of materials – their finish and their color – are most important in this regard. Specular materials, such as glossy finishes, reflect light as a mirror does, which can result in reflected images of the light source being visible ‘on’ the surface. Matte surfaces, such as natural stone, wood, and plaster, reflect light diffusely equally in all directions. Of the three aspects of color – hue, value, and intensity – value is the one that determines how much light is absorbed and how much is reflected. A white wall reflects approximately 82 percent of incident light, a light yellow wall 78 percent, and a dark green or blue wall 7 percent. 1 Colored surfaces lend some of their hue to light that is reflected.
A change in materials can alter the feeling of a room and the level of illumination as well. The cheapest wad to increase the amount of light in a dark room is to paint the room surfaces white. A dark room, on the other hand, can be created either by using little light in a white room or through dark surfaces. With dark surfaces, a room will look dark during both daytime and at night. With light or white surfaces, however, the effect changes depending upon the light sources used. This effect can be exploited. For example, the interior surfaces of the chapel of Notre Dame du Haut at Ronchamp are white, but due to the small quantity of daylight admitted, perceptually the surfaces grade horn light gray to dark gray.
Materials are important emotionally in relation to light. The sparkle of glass. the glitter of gold mosaics, the depths of dark polished wood, and the shadows on white walls all hold emotional messages. some of them connected with cultural settings, some of them connected to individual recollection. Some regions have building traditions and materials that respond to particular local conditions, such as the stucco alla veneziana favored by Carlo Scarpa. Requiring a labor-intensive process of application with very particular materials, the stucco ‘over time takes on a softer, more moist look, a quality of fantasy and beauty.’