"Saint Peter"
Ancient painting under glass, with a very fine line, depicting Saint Peter. The interesting peculiarity is that the artist, who paints on glass, must paint the figure in reverse, under the glass itself, as if it were a negative. Whoever observed the painting, even if delicate, could also touch it, unlike a painting on canvas or on glass itself. This form of painting was produced throughout Europe from the 15th century to the 19th century. 
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