The drawing features an almost identical layout to the final painting, just without the same colours that his oils would later deliver. Van Eyck focuses on the key facial features of this elderly gentleman who is dressed in a particularly simple loose-fitting shirt. The painting reveals this to be in two colours, a the plain design is in keeping within someone who is devoting their life to the word of God.
The artist used only silverpoint in this sketch, making it decidely simpler than some of the other drawings that remain from his career - they made use of many different mediums in order to complete the different sections of their compositions. The Royal Museum of Fine Arts Antwerp holds this piece alongside another of his drawings, Saint Barbara. These were believed to be the only two remaining drawings from his career until a third was recently attributed to him (and his studio), namely Crucifixion.
The style of this medium makes this depiction slightly more flattering, where aging lines are more subtle and harder to spot than in the painting that followed. Despite this, it is clear to see that this is an aging man whose facial features offer a lot of interest to a portrait painter, with his life almost captured through the various bumps and furrows that we see here. During this preparation study the artist actually left notes alongside the drawing to guide his later decisions on the painting, such as which colours to select.