Palmette and acanthus ornaments from the baptistery of San Giovanni in Laterano, pen testing marks

This sheet is so revealing because it documents a part of workshop practice otherwise rarely glimpsed at. Here we have a record of the draughtsman checking his drawing implement’s thickness before embarking on the actual drawing. The stick of red chalk was sharpened by hand – sharpeners as we know them did not yet exist. The tip could be sharpened through the abrasion of the flat sides on the scrap paper to form a point. This explains the repeated long straight strokes and looped lines.