To stain a piano bench, you first want to determine what kind of wood was used in its manufacture. Usually, it is advisable not to use stain on hardwoods such a mahogany, rosewood, or cherry. They generally will look fine if they are merely finished with a varnish made of polyurethane or shellac. However, stains are generally suggested for the enhancement of such woods as oak, beech, gum, ash, poplar, birch, pine or maple.
Penetrating Stains Made with an Oil Base
Oil-based, penetrating stains are typically made with turpentine combined with aniline dyes. These kinds of stains are popular among woodworkers, as they can easily be wiped on the wood, therefore they are not difficult to apply. However, you do have to wait some time before the stain sets, so don't plan on sitting on the piano bench until you make sure that it is completely dry. Once it is dry though, the stain does stay on the furniture and is hard to remove.
Pigmented Oil Gels
Another type of stain you can use on a piano bench is usually made of either mineral spirits, or linseed oil, added to pigment. The gel does not cost much and can be wiped onto the piano bench as well. This type of stain works best on woods such as pine or maple.