PFM: Stone Materials Must Matching Light
Stone Materials add interest to a  project, but achieving the right effect depends on how lighting is applied.

Matching Light and Materials

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.

Architectural Lighting

Several characteristics of materials should be understood when determining the lighting approach.

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.

 Lighting Methods

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).