Cast-in-place concrete incorporating architectural features is providing architects with a flexible new medium offering almost unlimited opportunity for originality. Additionally, concrete used in this fashion serves both as a structural material and as a facing. But even more important, the architectural and the structural features can be formed in the same operation. To obtain good architectural concrete, the architect and contractor must recognize the capabilities and the limitations of the materials with which they work. Concrete forming is a common operation, but for exposed work, formwork must be carefully erected and just as carefully stripped so that the surface comes out as planned. Any part of the formwork surface that is not in proper alignment will show up as an imperfection in the concrete. To overcome such problems, most prefab form manufactures have encased their plywood in a frame or have provided a means for proper alignment. In some instances, form joints and tie holes are left unfinished and no attempt made to conceal them. This technique can create a unique pattern but the job must be carefully planned and controlled. Form liners made up of undressed rough boards are also becoming increasingly popular. This is the famous beton brut or rough concrete technique. The lumber leaves a texture that resembles wood since it picks up the grain structure of the timber. Care must be taken to use the same type of wood throughout the job, especially on larger buildings where the wood may get repeated uses, because the lumber can absorb moisture and possibly affect the color of the concrete. Concrete placing and vibrating techniques can also affect the finished surface. Long drops of concrete should be avoided and concrete should not be dropped on the ties. Good vibrating is most important. If vibration is not carried out properly the surface of the concrete may develop large voids or honeycombing.