The technique of drawing on unprimed paper with pigments mixed in thinned oil is tricky. Too wet and the medium bleeds into the paper, too dry and the lines lack the fluency that is the whole point of drawing in this manner. Although Castiglione used no underdrawing in his oil studies, he did work systematically, first sketching the outlines with long, rapid strokes of dilute pigment, then gradually defining the details with shorter strokes of denser, drier colour. In the extraordinary drawings on display in this gallery, we can see Castiglione constantly testing the limits of the technique – exploring subtle variations of colour, the relationship between contour and modelling, and the effects obtainable with a wet or a drier mark. The reverse of the present sheet has been exposed to show how well Castiglione controlled the bleeding-through of the oil.