Plaster of Paris statues are generally made through casting, a process which makes for excellent reproduction of detail but which, with plaster, creates a brittle and fragile result. When plaster statues break into pieces or even lose parts, they can be repaired using a process involving gluing, rebuilding and reconstructing lost texture layers to make the fixed piece look seamless and as good as new.
Reattach any broken pieces using ceramic glue. Apply the glue to one side of each broken shard, then press it firmly into place against the broken patch of the statue where the piece originated. Use a damp rag to wipe away any glue that oozes out from the crack between the two pieces. Hold the piece in place until the glue sets; if necessary, secure the piece in place using masking tape until the glue dries, then remove the tape.
Prepare some air-dry clay for patching work. Soften the clay by kneading it in your hands. Moisten your hands as you do this so as to work enough water into the clay to make it soft and pliable enough that you can smear it as well as sculpt with it.
Apply the air-dry clay over the section that needs to be rebuilt. Press a blob of clay that's large enough to rebuild the missing sections over the area. Sculpt the clay into the shape of the missing piece, removing or adding extra clay as needed. Blend the clay at the joint by smearing it flat against the plaster with your finger. Let the clay dry to hardness according to the manufacturer's instructions.
Give the air-dry clay a coat of white acrylic paint; this will keep the darker colour of the clay from showing through after you apply the plaster over the top.
Mix a thick solution of plaster of Paris. Add just enough water to the powdered plaster to make a paste about the consistency of toothpaste.
Smooth the plaster solution over the repaired areas. Work the plaster into the cracks between the parts you glued back together and apply a coat over the top of the new clay pieces.