A lining on a window treatment acts as a buffer between the decorative face and the sun, the window glass, and any dust or dirt drifting through the open window. A lining also adds body to the window treatment and improves the way it hangs.
Some linings have special properties, such as resistance to water staining or ultraviolet rays. Other linings are insulated for energy conservation. Still others, known as blackout lings, completely block light.
Most lining fabrics for window treatments are made of cotton or a cotton-polyester blend. They're usually sateen, a type of strong, tightly woven fabric. Insulating and blackout linings are laminated with vinyl or layered with foam acrylic. Most lining fabrics are 48 or 54 inches wide.
White,off-white, and ecru are the most common colors, though fade-resistant colored linings are also available, usually by special order. For a uniform appearance from outdoors, use the same color lining for all window treatments.
Interlining is a soft, loosely woven fabric used between the lining and the face fabric to provide extra insulation and body. Since it's heavy, and interlined treatment must be securely hung.