Despite careful preparation, modern application technology and the use of sophisticated paint systems, defects can never be completely ruled out in vehicle refinishing. Nowadays, however, a professional bodyshop cannot afford to produce a poor quality finish. Moreover, it often takes a lot of time and effort to repair a defect. What caused the problem, what mistakes were made? How can these mistakes be avoided in future? Only when a defect has been correctly identified can the causes be eliminated and the painted object efficiently be repaired. Additionally, there is a broad range of environmental influences causing paint defects which need to be recognised and corrected.