Casing (molding)

Moulding (also spelled molding in the United States though usually not within the industry), also known as coving (United Kingdom, Australia), is a strip of material with various profiles used to cover transitions between surfaces or for decoration. It is traditionally made from solid milled wood or plaster, but may be made from plastic or reformed wood. In classical architecture and sculpture, the molding is often carved in marble or other stones.

A "sprung" molding has bevelled edges that allow mounting between two non-parallel planes (such as a wall and a ceiling), with an open space behind the molding. Other types of molding are referred to as "plain".

At their simplest, moldings are a means of applying light- and dark-shaded stripes to a structural object without having to change the material or apply pigments. The contrast of dark and light areas gives definition to the object.

Imagine the vertical surface of a wall lit by sunlight at an angle of about 45 degrees above the wall. Adding a small overhanging horizontal molding to the surface of the wall will introduce a dark horizontal shadow below the molding, which in consequence is called a fillet molding. Adding a vertical fillet to a horizontal surface will create a light vertical shadow. Graded shadows are possible by using moldings in different shapes: the concave cavetto molding produces a horizontal shadow that is darker at the top and lighter at the bottom; an ovolo (convex) molding makes a shadow that is lighter at the top and darker at the bottom. Other varieties of concave molding are the scotia and congé and other convex moldings the echinus, the torus and the astragal.

Placing an ovolo directly above a cavetto forms a smooth s-shaped curve with vertical ends that is called an ogee or cyma reversa molding. Its shadow appears as a band light at the top and bottom but dark in the interior. Similarly, a cavetto above an ovolo forms an s with horizontal ends, called a cyma or cyma recta. Its shadow shows two dark bands with a light interior.

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Wikipedia