What Is the Secret Ingredient Behind Rembrandt’s Golden Glow?

The characteristic golden hue in Rembrandt’s The Night Watch stems from an unlikely source. New research published in the journal Heritage Science suggests the 17th-century Dutch painter used arsenic pigments to add luster to his 1642 masterpiece.

Scientists examined the painting as part of Operation Night Watch, an ongoing study of the artwork conducted by the Rijksmuseum in Amsterdam. The Night Watch—Rembrandt’s most famous painting, according to the museum—is 12 feet tall and more than 14 feet long. It depicts a group of civic guardsmen, Amsterdam’s 17th-century local police force. Organized to watch over and protect their city, the guardsmen’s duties were “transformed into a dynamic drama by Rembrandt’s masterful shadow play,” writes Artnet News’ Adnan Qiblawi.

The painting’s lead character is the militia captain, who is dressed in black and giving orders. The second-most prominent figure is the lieutenant, who is dressed in light yellow gold. It was the lieutenant’s painted garb that captured the researchers’ attention.

Per the study, the researchers identified a mixture of yellow, orange and red particles in the pigments of the “doublet sleeves and embroidered buff coat worn by Lieutenant Willem van Ruytenburch.” After examining these details with high-tech instruments, they found the particles contained pararealgar, a naturally occurring arsenic sulfide mineral.

To create the perfect reflective paint for the lieutenant’s uniform, the team concluded, Rembrandt mixed pararealgar and semi-amorphous pararealgar—mineral variants that are naturally yellow and reddish-orange—with lead-tin yellow and vermilion, reports Hyperallergic’s Rhea Nayyar.

The researchers expected to find not pararealgar, but rather orpiment, an arsenic-laden mineral that Rembrandt used in later paintings like The Jewish Bride. After discovering the pararealgar and semi-amorphous pararealgar, the scientists researched the availability and use of both of these mineral pigments in the 1600s.

“Our research involved examining 17th-century trade records, apothecary pharmacopeias, price lists and contemporary writings on metallurgy,” lead author Nouchka de Keyser, an Operation Night Watch team member, tells Hyperallergic. The researchers also combed through painters’ manuals and alchemical literature, including Danish historian Ole Worm’s Museum Wormianum.

Rembrandt’s mysterious materials are a main focus of Operation Night Watch, as their identification is crucial to the painting’s conservation and restoration. Last year, a separate study found that The Night Watch’s canvas was prepared with lead-based and quartz-clay layers.

As De Keyser tells Hyperallergic, the most recent investigation of the painting’s pararealgar pigments involved hunting for their origins: where they were made and sold, their price, and how Rembrandt acquired them.

“We also studied a 17th-century collector’s cabinet from the Rijksmuseum, which includes various types of arsenic sulfides, hoping to match them with the pigments found in Rembrandt’s painting,” De Keyser says. “This deep dive into the historical sources really allowed us to piece together a more comprehensive picture of these pigments in the market and how Rembrandt ended up using them.”

Sonja Anderson | READ MORE

Sonja Anderson is a writer and reporter based in New York City.