Selecting a finishing system for doors, trim, paneling, cabinets and furniture for a project is not an easy task. Project finishing can play a large part in enhancing the beauty of wood and in enhancing its durability. If you are following AWI guidelines, then the following items should be specified for every project.
Most architectural woodwork is custom grade, with premium grade reserved for special projects or focal points, and economy representing the minimum expectation of quality, workmanship, materials and installation. For example, in custom grade millwork the gap between doors, drawers or panels and frames must be 1/16" or less. In premium grade work, the tolerance is 1/32"; in economy, 3/32" is acceptable.
The color of a finished piece is affected by the finish's sheen and by the light in which it is viewed. Changes in color created by ambient light are called "metamerism." Almost everyone sees color differently, and as people age their color perceptions change. In many cases, the more complex the coloring process, the more color will vary depending on the light source. For this reason, many stains are made with four or fewer pigments. The fewer the pigments, the less the finish will be affected by changes in light.
When reviewing stain samples, be sure to use the same type of light source as that in which the work will be viewed when the project is completed. Daylight is quite different from Deluxe Warm White fluorescent bulbs or incandescent bulbs.
Gloss also may affect color. Flat or satin finishes will appear darker than gloss or semi-gloss top coats. In areas where natural light is mixed with electric lights, attempt to have the color of the electric light match the color of the natural light.
In all cases where finishes are in contact with sunlight, an ultraviolet blocker in the finish will help the colorant from changing, as well as keep the finish from yellowing.
The term "color match" is often misleading. The best case achievable using a natural product like wood in a wide variety of lighting conditions is a good "blend" of color and tone throughout the project area. The wood products' natural color is altered by the application of a "clear" topcoat, along with stains, glazes, bleaches, etc. Apparently consistent color is a combination of light reflection, cellular structure, natural characteristics, applied colors and sheen.
No wood, wood finish, or stain is completely "color-fast" if that is defined as "no change of color over time." Raw wood without a stain or finish will change color in reaction to ambient conditions. The addition of stains and/or topcoats will change the rate at which the transformation will occur, but will seldom stop it. For this reason, it is advised to keep stain and finish samples covered and in a dark place if they are to be used for comparison to the finished work.
The four main groupings for gloss which are used in the AWI Quality Standards and are accepted by the industry are:
Most resins dry with a gloss or semi-gloss finish. Flattening paste or particles can be added to the finish to reduce the gloss. Another method is to spray a gloss finish, and then rub it with a compound such as Tripoli or Rotten stone parallel to the grain.
Surface effect is the term given to how many pores are visible as indentations after finishing. On ring-porous or open-pored woods such as oak or ash, even heavy finishes will not completely fill the pores. If the desired effect is to have a very natural look, then specify open pores. If you want only some of the pores to show, specify semi-filled pores. However, if no pores are to show through the surface, then specify filled pores.