Quotation from: The Notebooks of Leonardo Da Vinci
Written by: Leonardo da Vinci
631.
Since walnuts are enveloped in a thin rind, which partakes of the
nature of ..., if you do not remove it when you make the oil from
them, this skin tinges the oil, and when you work with it this skin
separates from the oil and rises to the surface of the painting, and
this is what makes it change.