According to DIY Data, there are several types of materials used to create a finish for a wood surface, including dyes and stains, varnishes, polishes and oils. Some oil finishes utilize materials like linseed oil or lemon oil mixed with water. When the water evaporates, the oil soaks into the wood surface. Acrylic-based finishes sit on the surface of a wood like paint.
According to Wood Finish Supply, a proper finish for wood surfaces consists of at least one "base" coat, a number of "build" coats and a "top" coat. The base coat provides the finish with a foundation. Build coats give the finish structure, and top coats give the finish its look (e.g. gloss, matte).
The first coating used to provide the finish for a wood surface evens out the differences in the surface's density and porosity, according to Wood Finish Supply. Two primary coatings are often required on softer woods. Build coats provide durability and moisture resistance to a finish. According to Wood Finish Supply, in building a finish where the wood grain is to be visible, only gloss should be employed for base coats.
According to Wood Iron, a decent exterior wood finish should enhance the wood's character and not cover it up. It should be relatively easy to maintain and recoat an exterior wood finish without running into problems or high costs. A finish should be durable enough to last for between 3 and 5 years on a vertical wood surface and 1 to 2 years on a horizontal surface, according to Wood Iron.
Finishes need to be applied to wood surfaces correctly to remain effective. Wood surfaces should be cleaned before the application of a finish. The surface should also be thoroughly dried before the application of the finish. Wood Iron recommends that finishes not be applied in direct sunlight as it may compromise the finish because the solvents found within the finish evaporate too quickly.