You can tell an original artist painting from a copy using a four-step examination process that the Traditional Fine Arts Organization recommends. If you are still unsure after your personal examination, take the artwork to a professional appraiser to determine authenticity and provenance.
Reproductions often have machine-printed issue numbers, stock identification numbers, copyright dates, or the artist's name and the work title on the reverse side or in small type along an edge. An original artist painting has a hand stamp with signature on the reverse or a signature and date painted onto the artwork's surface.
Examine the material used for the artwork. An original painting traditionally uses canvas, but reproductions often use paper, fiberboard or cardboard. If the work uses canvas, hold it up to a bright light with the picture surface toward the light. Reproductions show an even picture easily seen through the canvas in reverse.
Examine the picture for evidence of paint rather than printing. An original painting has a rough, uneven surface from the media and brush strokes. When viewed from an angle, an original watercolor's surface appears rough, while the sides of the canvas of an original oil painting show rough paint edges. Reproductions appear flat and even.
Use a high-power magnifying glass, such as those jewelers use, to view the picture side. If you see an array of microscopic colored dots in a pattern, you have a machine-made reproduction. A giclee print, a high-quality digital print equivalent to 1,800 dots per inch, doesn't show dots but may have dabs of paint over the print in an uneven distribution and in an unnatural brush-stroke pattern. The artist may sign a giclee print.