If you want to hang pictures or artwork on a plaster wall without damaging it, there are a few preventive measures you should take to protect the wall.
Determine the Weight of the Object to Be Hung
Plaster walls are not extremely strong when it comes to hanging things on them. While it is perfectly acceptable to hang very lightweight framed posters or framed artwork from a plaster wall, anything heavier will require more than a simple nail in the wall. Otherwise, you run the risk not only of the artwork falling down but the wall being left with a huge gash where the nail was located.
If you have an especially heavy painting or framed piece of art, you will need to use a wall hanger that provides support for the entire wall where you have made the hanger hole.
There are several different types of wall hangers available to use for hanging artwork.
Detachable Plastic Hangers
These types of wall hangers are good for light to medium weight wall hangings. They attach to the wall with a self-adhesive pad and the newer plastic hangers are detachable without leaving any damage to the wall.
Counterweight Metal Hangers
Counterweight hangers are very deceptive looking. These are a very slim piece of metal wire that is shaped like a large fish hook. They are inserted into the plaster wall so that the long portion of the hook is inside and against the interior of the wall. Counterweight hooks can usually hold up to 100 pounds without damaging the walls. When you remove them, you have a very small pinhole in the wall that can easily be covered with a small dab of spackle.
For very heavy items, it is necessary to install a wall anchor. Wall anchors are made of either plastic or metal and are slightly smaller than the screw you will use to attach the hanging to the wall. To use a wall anchor, drill a small hole into the wall plaster where you will hang the item. Push the anchor into the hole and then screw the supporting hanger into place. As the screw is pressed into the anchor, it will expand and create additional support in the wall. Unfortunately, anchors are usually left permanently in walls, although they can be covered with spackle and painted over.