Creating a luminous effect with pastels can be achieved through the fracturing of local color while retaining value consistency. Pastel, being a dry medium, allows us to utilize clean bold pigment applications with less of a concern for the fussing that often leads to a muddied effect in wet mediums.
When light is strong or highly reflected off a variety of surfaces, it can appear to glow. The easiest way to duplicate this in a pastel painting is to use a variety of colors in any given area without changing the value. Value represents the weight or form of the object. Tampering with it will make the structure fall apart, producing an amateurish look. Sir Isaac Newton proved that white light is made up of all color. When he bent the light, it separated into individual colors, producing a rainbow effect. Light is also energy. It’s a pulsation—striking and reflecting off surfaces throughout our field of vision.
Being unable to physically capture this energy force and apply it our pastel surfaces, we rely on a few techniques that help in creating a luminous appearance. Fragmenting, or pulling colors apart, within an area, especially one that is made up of considerable illumination, will help to represent the energy and substance of real light creating more luminosity. This works very well in areas like the sky or highly reflective surfaces like water. If the sky is blue, fracture the color into its analogous or neighbor hues: blue, blue-violet, and blue-green, but retain its value. If the value is correct, the area will have the right weight and the fractured color will pulsate, visually blending together creating a more luminous appearance. This can be done with any area within a painting but works exceptionally well when it is filled with light. Be aware of the chroma (brightness) of the color choices. Try to stay close in saturation, so that the fractured colors relate and easily blend together visually.
Another means of heightening the appearance of a glow or luminosity is to create a halcyon effect. Instead of creating a hard edge all around an object, soften or blur the edge near a highlight, as the light would reflect off the surface. This blur will give the appearance of light bouncing off the object, creating a strong glowing effect. This
works very well on objects or surfaces that have a strong curve and the light is striking them from an angle. I like to thing of the light as a forcefully thrown ball. When it hits the surface, where would it bounce? Place a little smudge there.