1. Rough plaster: The irregularities in rough, or sand-finished, plaster produce an effect of texture that makes such a wall an attractive background. The natural color of rough plaster varies according to the color of the sand used in mixing it. Sometimes it is a pure gray, sometimes it is tinged with soft tones of warm color. Powdered color may be mixed with the plaster when it is wet, if the mason is sufficiently experienced to handle it. Rough plaster should be applied by a skillful workman in order to produce a uniform effect. Rough plaster is rather harsh in texture and is not suitable in all rooms or with all woods. It is more akin to hard woods like oak, waxed or stained, than to mahogany or satinwood or painted woods. It is incongruous with delicate or very luxurious hangings. It is better in family rooms than in bedrooms or small rooms in which hands come often in contact with the wall. If rough plaster is spotted or discolored, it is not so easy to clean as smooth plaster. If the discoloration is only on the surface, it may be removed by pumice stone.
If it is desired to change the color of rough plastered walls, oil paint is a very good medium; a coat of glue-size applied before the paint will facilitate the work and will economize the amount of paint.
2. Smooth plaster: Walls finished in smooth plaster present an even flat surface, not so interesting as the rough plaster, but with many advantages. It is easier to apply and is easily cleaned. Smooth plaster should be painted or papered, since its glaring white surface is a trying element in almost any color scheme.
3. Smooth plaster painted (oil color or water color): Paint has an advantage over paper in that any subtlety of tint or tone may be obtained through skillful mixing. In general, in the use of house paint, white will lighten any color and black will darken any color; but in the case of the yellows, since black paint tends to develop green shades in them, dark brown paint should be substituted for the black. Oil color is more durable than water color. Although oil paint is more expensive in the beginning than water color, it is more economical in the end for use in rooms that are constantly occupied, or on parts of walls that are subject to the frequent contact of hands or furniture, such as schoolrooms, nurseries, kitchens, or corridors.
Oil color sometimes has a disagreeable shine. This may be avoided by adding turpentine or by flat finishing (pouncing with a broad flat bristle brush). Oil colors may be obtained already mixed, but they frequently vary from sample. A better plan is to buy the ingredients and have them mixed only a short time before using. Different surfaces require different proportions of paint, oil, turpentine, and the like. An even tone throughout the room is always safe, but a very attractive effect may be obtained by an uneven tone. For example, the walls might be painted a gray blue and stippled with a gray green. Such treatment produces an effect of atmosphere suggesting space. It should never be attempted except by an experienced painter. Oil color is easily cleaned by washing with soap and water.
Water color, or calcimine, has the advantage of being inexpensive, and less skill is required in applying it. Water color may be applied over other surfaces, such as paper, beaver-board, or calcimine, but wall paper should not be put on over calcimine as it is likely to strip off. Water color walls cannot be washed but can be easily freshened by the application of a second coat. Water color is the most common treatment for ceilings even though the side walls may be painted or papered.
4. Paper or textiles: Smooth plastered walls are often covered with paper or a textile; this treatment is effective in many furnishing schemes and is especially adaptable in old houses.