Restoring antique gold picture frames is challenging because it requires matching both the tone of the gold used in the frame and repairing the underlying damage. However, it is rewarding in that a little work can make a big difference.
Clean the frame. The first step is to clean the frame and remove dirt and dust. A moist cotton swab will be sufficient.
Identify areas of missing plaster. Generally, antique picture frames are wood with plaster moulding. Typically breaks occur in the plaster, as plaster is more fragile than wood. Look for areas where the plaster is missing.
Fill in the missing plaster with epoxy. A silicone epoxy can be used to fill in the missing areas in the plaster. A toothpick can be used to model the silicone to match the surrounding plaster. Let this dry for at least 48 hours.
Recolor the epoxy to match the frame. You can use either gold paint and blend it into the area, or use gold leaf. The process for gold leaf often involves a base step of putting down red ground, which will be included in a gold leaf kit.
Spray the whole frame. Once the areas are patched, a varnish spray, either matt or glossy depending on your taste, can be used to seal the paint and to give a uniform lustre.