Wood furniture does best in rooms with moderate humidity. If your home becomes too dry in the winter, the wood could dry out and crack. If this is a chronic condition in your house, consider getting a humidifier. Wood furniture's other natural enemy is direct sunlight, which can bleach or discolor the wood over an extended period. Arrange your furniture so your fine wood pieces are tucked away on the sides of the room and reserve the window area for glass, metal, or upholstered pieces. Certain types of spills are particularly bad for wood finishes, so wipe them up as soon as they happen. Milk can harm wood finishes. If you get a milk stain, rub it with a damp cloth dipped in ammonia, then dry the area with a soft cloth. Alcohol can dissolve some finishes. Wipe up spills from drinks, medicines, and cosmetics immediately, then rub the area with a cloth moistened with lemon oil. Coasters are an inexpensive way to protect wood surfaces. If you forget to use them, glass rings can be removed by rubbing with a mixture of mayonnaise and white toothpaste. Wipe the area dry, then polish the entire surface. Most furniture polish will have either an oil or a wax base. Both work equally well, but choose one type and stick with it. Switching back and forth between the two can cause blotches on your wood finish.