 Only once did Leonardo use vellum and old sheets of it are easily acquired by forgers.Leonardo scholar Pietro C. Marani discounts the significance of the drawing being made by a left-handed artist, noting that imitators of Leonardo's work have emulated this characteristic in the past.Marani is also troubled by use of vellum, "monotonous" detail, use of colored pigments in specific areas, firmness of touch and lack of craquelure.