Finishes are substances applied to the exterior of wood furniture in order to protect the furniture and prevent the onset of serious problems, such as cracking, drying, swelling or general deterioration. Not all types of finishes work equally well for all circumstances, or for all types of wood. Homeowners and other furniture refinishers do best when they choose a finish that closely matches the needs of their current project.

Finishes come in two main forms, known generally as surface finishes and penetrating finishes. As their names imply, surface finishes stay on the surface of wood, when applied, while penetrating finishes seep further into wood before drying. Common types of surface finishes include varnish and shellac. These products, which are typically applied with a natural or synthetic brush, provide superior wood protection and can help reduce signs of wear on frequently used pieces of furniture. However, when applied, surface finishes tend to give furniture a more artificial appearance, than penetrating finishes. It also takes more skill to apply a surface finish, than it takes to apply a penetrating finish.

Common types of penetrating finish include tung oil, Danish oil and linseed oil. These products are typically applied with rags, rather than with brushes. Because of their appearance when dry, penetrating finishes can easily enhance the look of antiques and other kinds of fine furniture; for this reason, antique restorers commonly use these finishes. However, penetrating products can also cause certain problems. For instance, tung oil can look dull, if applied too thickly, while linseed oil can make furniture feel sticky, when exposed to a high humidity climate. 

When applying a finish to wood furniture, homeowners and other consumers also need to consider whether or not they want the natural grain of the wood to show through, when finishing is done. In a finish application called an open grain finish, the person carrying out the project puts on a clear finish, usually after staining the wood. This type of finish emphasizes the grain of the wood and gives the piece of furniture the distinctive look associated with that particular wood species. In another finish application, called a closed grain finish, a substance called grain filler is applied, between staining and finishing. This filler effectively levels out the underlying grain and de-emphasizes grain differences between wood species. Professionals working on piano restoration projects commonly use a closed grain finish to achieve a more upscale appearance.

Instead of doing their own refinishing projects, some consumers turn to professionals who specialize in refinishing, antique restoration and/or furniture repair. Full-service professionals can handle all of these types of projects and produce top-notch results, regardless of the complexity of a given job. Qualified furniture restoration and repair professionals can also take over home projects started by their customers, correct most problems, and return the furniture in excellent condition. They can also act as information resources, for their clients and for the general public, and increase general awareness about appropriate finish choices and a variety of other furniture-related topics.