A furniture piece must be at least 100 years old to qualify as an antique [source: Wagoner]. Museum-quality items should always be restored by a professional. By refinishing common antiques at home, you risk making a mistake that can lower its value, damage the patina that gives it an old look and proves its age, overdo the restoration by replacing more than necessary, or harm the wood's aging process or finish. If you don't know what to look for, you can sand or scrape away desirable marks of age like small, concave grooves created by jack planes used a century ago or numbers chiseled into items in a furniture set to mark their order.
"No inexperienced person should try to restore antique furniture. Period," says Clinton Howell, a member of the National Antique and Art Dealers Association of America, "How many people feel that they could do as good a job defending themselves as their lawyer?"