Moulding is decorative trim and edging added to architectural feature like walls, doors, cabinets, and other furniture.
Historically, moulding was cut into solid boards, which were then installed on the walls. Today, the pratice is to assemble similar shapes using smaller pieces of trim, building up the profile using pre-shaped pieces of wood. Another alternative for edging a board is to use a router to carve the edges of boards in much the same way as the older moulding planes.
Moulding is added to walls for reasons both practical and decorative. Working from the ceiling down:
*Cornice or crown moulding covers the connection between wall and ceiling, In some periods in might be made of molded plaster, but more often cornice is made of wood.
*Picture moulding is used to support picture frames suspended on wire from picture hooks, which in turn are bent to hook on to the molding. This avoids nailing into plaster walls, and can support large or heavy pictures.
*Chair rail is used to prevent chair backs from marring the plaster when a chair is pushed against the wall. The installed height of chair rail is dictated by the style of chair used in the room.
*Wainscoating is a wood paneling applied to the lower portion of a wall. It is both decorative and more resistant to damage than plaster. It has been in and out of fashion in many periods.
*Baseboards cover the seam between walls and floors. As these are usually of different materials, e.g. plater and wood, so actually joining them is usually impossible. Baseboards serve to hide this joint. They are also called mop-boards, as they also protect the wall from wet floor mops.
*Floor moulding is used to finish the transiton beween baseboard and floor. It's purpose was originally practical. In its original form, floor molding was a shoe which was nailed to the floor. It had a rabbet plowed into the wall side which held the baseboard set into the groove. Today it is decorative, and is usually a small quarter-round or cove moulding added to provide a similar appearance.
As stated above, Cornice is used to finish the joint between walls and ceiling. It can be useful in theatre to finish the top of walls in box sets, and provide the illusion of a ceiling.
Cornice can be built up using smaller commercial moulding pieces. A framework is made by building a frame of profile pieces attached every few feet to a spine of 1x3. The molding pieces are then attached to the frame to create the finished profile. After painting, the cornice is attached to the top rail of the flats using short bolts.
Another technique for creating lightweight cornice is to carve foam billets to shape. A "hot knife" cutter is sometimes used for this. A metal strap bent to the desired shape is used as the knife, and a special tranformer is used to run enough electricity through the metal strap to heat it hot enough to melt it's way through the foam. This can be dangerous if the wrong equipment is used, and the exact procedure is beyond the scope of this course.
Large foam cornice can also be laid up using sheets and strips cut to size with a table saw, with split ethafoam rod as half- and quarter-round, and with PL-300 as adhesive.
Both types of foam cornice will need to be treated to make it take paint. This can be done using flexglue and tissue as a surface skin, or by priming with "Foamcoat" or Sculp-tor-cote" before painting.
Routers and shapers are motorized tools which use a rapidly spinning cutter to gouge a particular shape into a board. Routers are usually hand-held tools, while shapers are table mounted cutters and a guide fence to do the same job. Shaper cutters are usually similar but larger than router bits, and Shapers are frequently more powerful and able to handle larger jobs. Routers are especially useful for cutting moulding into the edges of shelves, table tops, and other furniture parts.
Router and shaper bits come in many standardized sizes and shapes, and custom shapes can also be obtained (at a high price!). For theatrical purposes, it is usually sufficient to cut some detail with standard bits in to an edge, and then build up additional detail with additional commercial moulding until the desired profile is achieved.