I want to know the answer to the following question:
What technique is used in art to examine underlying layers of a painting without damaging it?
All the background I'm provided with is that "Infrared reflectography (fr; it; es), as called by art conservators, can be applied to paintings to reveal underlying layers in a completely non-destructive manner, in particular the underdrawing or outline drawn by the artist as a guide.". Is that enough to answer the question?