Context: 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. This often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting. Art conservators are looking to see whether the visible layers of paint differ from the underdrawing or layers in between – such alterations are called pentimenti when made by the original artist. This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti the more likely a painting is to be the prime version. It also gives useful insights into working practices.

Question: What technique is used in art to examine underlying layers of a painting without damaging it?
Answer: Infrared reflectography

Question: What shows up particularly well in reflectograms?
Answer: carbon black

Question: What is the term for differences in the painting and underdrawing made by the original artist?
Answer: pentimenti

Question: What painting technique is used to reveal working practices?
Answer: Unanswerable

Question: What is visible in alterations of paintings?
Answer: Unanswerable

Question: What is it called when visible layers differ from the reflectogram?
Answer: Unanswerable

Question: What is useful to show if a painting is original or part of a reflectogram?
Answer: Unanswerable

Question: With carbon black what is the painting more likely to be?
Answer: Unanswerable