Wood varies substantially from species to species and sometimes within the same species. Understanding these differences and how they can affect the finishing process may mean the difference between a fine finish and an unacceptable one.
Wood is finished to protect it from weather, wear, dirt and other common hazards. Wood is also finished to enhance its natural beauty or, in some cases, to make a less expensive wood look like a more costly one. Regardless, anyone involved in wood finishing knows that this material varies substantially from species to species and sometimes within the same species. If this variation is not understood and accounted for, producing a quality product will be difficult.
There are two broad categories of variation. First, wood is a natural, biological material and thus its properties are expected to vary. Some important properties include the presence of extractives, grain orientation, porosity, dimensional change and color. Second, the process and care that is used in manufacturing wood from standing trees to create a product ready to be finished can also result in substantial variation. Some examples include the method and care used to cut boards and veneer from a log, drying, gluing techniques and sanding.