If your home is over 50 years old, there is a good chance it may have plaster walls. Made from the mineral gypsum, plaster is essentially reconstituted rock, making it an extremely durable and hard surface. These admirable qualities can make hammering a nail into its surface a challenge. Without proper care, your first experience with nailing into plaster may produce a cracked wall or a hammer that practically bounces off the nail.
While plaster is an extremely hard surface, it is supported by a series of wood strips known as lath. Accidentally hitting a section of lath may cause a vibration and loosen the plaster away from the lath. This may not only cause a crack in your wall, it could compromise large sections of plaster. Be aware that plaster can behave differently in different locations -- one method may work well in one place and cause problems in another.
Small Picture Hooks
Small and lightweight pictures with picture wire can usually be installed fairly easily with just a hammer. Use the hook as a guide to hammer the small nail diagonally into the wall. Keep in mind the weight rating for picture hooks is based on the item being hung and does not take into consideration the structure of the wall. Consider using two hooks for larger pictures to keep your picture hanging straight and distribute the weight of the picture on the wall.
Place a small piece of masking tape on the area in which you intend to hammer the nail. The masking tape gives the surrounding plaster extra support and minimizes flaking and cracking. Position the nail at a 45-degree, upward angle and gently tap the nail. If the hammer seems to bounce back, you may be over a wood lath. Move the nail an inch or two and try again. Remove the tape once the nail is in place.
Drill a pilot hole before hammering larger nails into plaster. The hole does not need to be deep. You only need to drill through the top coat of the plaster. As soon as you see brown dust, you are into the second layer. Place the tip of the nail in the pilot hole and gently tap the nail into place.