Heads of Sts Thomas and James the Greater

surface prep

Select a toned paper (grey or warm brown) that provides a mid-tone ground. Leonardo’s practice involved using the paper tone as the middle value, adding white for highlights and black for shadows. This aligns with the description of his large drawing using 'black chalk on coloured paper' (Source 5). Ensure the paper has a slight tooth to hold the chalk but is smooth enough for fine blending.

underdrawing

Begin with a loose, structural underdrawing using charcoal. Focus on the 'keen sense of construction' and the 'bony structure of the skeleton' and 'location, attachment and function of the muscles' as emphasized in drawing theory (Source 3). Do not focus on fine details initially; instead, establish the proportions and the 'three dimensions — length, breadth, and depth' (Source 3). Leonardo’s studies were often based on observation of live models, so use a reference or model to capture the specific character and action of the heads (Source 5).

underpainting

Not applicable for dry media drawing. However, the concept of building up tone from the mid-tone of the paper serves a similar function to an underpainting in oil, establishing the value structure before refining details.

Sfumato

A technique of subtle shading that creates a soft transition between colors and tones, eliminating harsh lines. Leonardo used this in his large drawings, such as 'The Virgin and Child with Saint Anne' (Source 5).

Structural Drawing

Building the figure from an understanding of anatomy, including the 'bony structure of the skeleton' and 'muscles' (Source 3). This ensures the form is solid and three-dimensional.

Observational Study

Leonardo often drew from live models or observed faces in public to capture realistic character and expression (Source 5).