On Painting: The Beauty of Colour, Lustre and Reflected Light
Why highlights, transparency and reflections carry a colour's greatest beauty
Under the heading De pittura, Leonardo argues that the greatest beauty of a colour lies in its principal lights, and that a highlight (lustro) takes far more the colour of the light illuminating a body than of the body itself. He distinguishes the highlights of metals, leaves, glass and gems, and praises the beauty of reflected lights in transparent bodies such as the balas ruby and in the folds of spun gold, where surfaces reflect into one another to infinity. He closes by noting that a lustrous or transparent body cannot receive a cast shadow, just as the shadow of a bridge is seen only on turbid, never on clear, water.
On this page
The greatest beauty of colour lies in the principal lights
Leonardo states that the colour lying between the shadowed and illuminated parts of a body is of lesser beauty than the fully lit colour, so the first beauty of colours resides in the principal lights.
Lustre partakes of the illuminating light, not of the body
The highlight (lustro) partakes far more of the colour of the light that illuminates a dense body than of the body's own colour. On burnished gold, silver and other metals the lustre is entirely the colour of the lit body, while on leaves, glass and gems it takes little of the body and much of the illuminating light.
Reflected light and transparency: balas ruby, glass, spun gold
Lustre formed in the depth of dense transparent bodies, such as the balas ruby and glass, stands in the first degree of a colour's beauty because the eye sees it through the body's whole natural colour. Reflected lights in the folds of spun gold surpass the body's natural colour, one surface reflecting into another set opposite to it, and so to infinity.
No cast shadow falls on a lustrous or transparent body
No lustrous and transparent body can display upon itself a shadow received from another object. As proof, the shadows of river bridges are seen only upon turbid water and never appear on clear water.