The alchemist in his laboratory was a popular subject for Dutch painters of the 17th century because it allowed them to show off their skill with light. Mattheus van Helmont’s A Savant in His Cabinet, Surrounded by Chemical and Other Apparatus, Examining a Flask (1670s), one of the splendid plates in Philip Ball’s introduction to alchemy, depicts an alchemist at work, brandishing a beaker of pale blue fluid in one hand, surrounded by the implements of his craft.