COMMON PAINTING PROBLEMS
Repaint. Broadly defined, repaint is any paint applied to an artwork by someone other than the artist. Modern conservation practice dictates that repaint be applied only to those portions of a paint film that have been damaged; this process is called "inpainting" and it is usually done with tiny dots of paints that are formulated to be removable in the future. Unfortunately, many restorers in the past were very liberal in their application of repaint, often covering large passages of original image with paint that became difficult or impossible to remove as it aged. (Even today, there are restorers who do this.) Conservation treatment often includes removal (or partial removal) of old repaint, usually followed by careful inpainting of damaged areas.
About the photos. The photos on the right are all detail shots of severely damaged paintings. In the "before treatment" shots, the massive and very poorly done repaint of past restorers is obvious. The "windows" in the "before treatment" shot of the angel are cleaning tests; white areas are fills added by the restorer to compensate for missing paint. Where original paint is still present, it is very different in color than the repaint applied over it.