Materials add interest to a project, but achieving the right effect depends on how lighting is applied.

BY Glenn Shrum

» Many architects and interior designers believe that the selection of materials and finishes is among the most important decisions made during a project. Without illumination, however, we cannot perceive the aesthetic characteristics of any material, so it stands to reason that the appropriate lighting is essential to maximize the impact of architectural finishes. Several characteristics of materials should be understood when determining the lighting approach.

texture Shadows caused by variation in surface texture create contrast that allows the viewer to perceive depth in a material. The position of the light source determines the length of shadow, rendering the surface with varying degrees of definition.

surface reflectance How an opaque material reflects light determines the viewer's perception of the illumination present at its surface. While a mirrored, or highly specular, surface is most able to reflect view, it will appear dark if the environment seen in reflection is not illuminated, even if light is present on the surface. Matte or diffuse materials reflect light equally in many directions, resulting in a similar light quality from many points of view.

color Every object absorbs some of the light that strikes it. The pigment within a surface determines how much and which components of the visible spectrum reach the eye. Generally speaking, dark colors absorb more illumination than their lighter counterparts.

light transmission Transparent and translucent materials allow light to pass through them. The internal composition of these materials influences the amount and quality of light transmitted.

The designer must decide how to light a material based on which combination of these characteristics are present. Typical lighting methods that can be employed include wall grazing (the illumination of a vertical surface at a very steep angle); accent lighting (lighting an object or surface from an angle that is between 30 and 45 degrees off the vertical axis of the primary view); wallwashing (the 'even' illumination of a wall surface from a flat angle. For the purposes of this discussion, accent lighting and wallwashing have the same effect on a material when viewed at eye level); and ambient lighting (indirect illumination resulting from light reflecting off another surface before striking the material in question). Let us now consider how to apply these principles when illuminating typical building materials.

The quality of the craftsmanship is a primary concern when lighting plaster and gypsum-board surfaces. Wall grazing typical gypsum board construction will expose unattractive variations in the surface finish that would remain imperceptible under ambient or wallwashing conditions. Occasionally, plaster is specified with an intentional variation in texture or a polished surface treatment. Skillfully applied by decorative plaster artisans, these surfaces look best when grazed with light.

When considering options for illuminating stone materials, the lighting designer should understand the architectural intent and type of finish. If stone was selected for its natural character, locating light fixtures close to the surface will reveal the organic texture. The same material illuminated with a diffuse ambient light will appear less dramatic. Whether selected for easy maintenance or its high-end associations, highly polished stone is specified in many architectural applications. Special care should be taken to avoid veiling reflections of the light source that occur when wallwashing such a surface. Honed finishes offer the lighting designer an opportunity to reveal the specular components present in many stone types without the reflected glare.

Metal materials with specular finishes are often used to create an interestingly illuminated surface without direct light. The same mirror-like qualities that allow this effect can result in glare if not considered carefully. The addition of micro texture on metal surfaces spreads the reflected light into multiple directions, resulting in a surface that appears bright from many points of view. Depending on the position of the light source, different areas of the orbital sanded pattern seen in image catch the light. image shows the same orbital material with the addition of a uniform surface treatment. By adding this texture, the entire surface appears brighter. The effect is similar to adding a satin finish to reflective surfaces.

The color, scale, and reflective qualities of the weave should be considered when lighting architectural fabrics. If the material is opaque, very dense, and has a matte finish, any lighting approach will have similar results. Metal fabrics offer some insight into the opportunities that exist when lighting a highly specular, open-weave fabric. As a result of their reflective qualities, the warp (vertical braided cables) and weft (horizontal bars) appear differently depending on the size and color of the light source. A halogen point source makes the texture appear more flat than the same material under fluorescent ambient lighting conditions. Depending on the architectural application, scale of the weave, and position of the viewer, principles of this scrim effect may apply when lighting fabric.

When backlighting architectural plastics, the viewer's ability to discern the light source, its position, and its size should be taken into consideration. Whether the lighting design intent is to illuminate the surface uniformly or to reveal a view of the lamp image, some specific characteristics of the translucent material are of concern. The internal structure of a cellular acrylic creates a pattern of shadows that reinforces the viewer's awareness of the position of a light source beyond. The more consistent gradient of light found in backlit solid core materials, like etched acrylic panels, lends itself to situations for which a more uniform light distribution is preferred.

Designers should consider the fixture's internal structure and the lamp image when lighting translucent glass; the surface qualities of glass can also impact the lighting scheme. A smooth glass surface will function like a mirror, depending on the lighting condition and the viewer's position. This type of glass appears much the same as plastics when backlit. When lighting textured glass, it is possible to make the surface glow by locating the light source at the material's edge or at a grazing angle.

Projects often come in over budget, and when this happens, architectural finishes and lighting are among the first items to be reconsidered. An integrated approach to the selection of materials and lighting best serves the project design and budget goals, since without the appropriate lighting, materials cannot achieve their full aesthetic potential. These two architectural elements should always be considered together.

Educated as an architect, Glenn Shrum worked as a lighting and exhibition designer at George Sexton Associates for four years before joining Ziger/Snead Architects in 2001. In his current position, Shrum is responsible for the lighting design of all the firm's work and architectural and exhibition design for select projects. In 2004, he received a grant from the Nuckolls Fund for Lighting Education for his course, 'Lighting Concepts and Applications,' at the Maryland Institute College of Art.