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.

Upon analyzing the yellow bit, DePhillips discovered that it was lead tin yellow. Why? Because lead tin yellow came into use during the second quarter of the 15th century and by 1710 had never been ...