Final answer:
Painters used lead strips to add details to stained glass windows, a crucial component in the art form that secured the colored glass pieces to create detailed designs.
Step-by-step explanation:
Painters used lead strips to add details to stained glass windows. These strips were essential in the construction of stained glass art, serving as the framework that held the differently colored glass pieces in place to form intricate designs and images. This technique was especially prominent in the design of Gothic cathedral windows, where the stained glass often depicted religious narratives and figures. Secular architecture also utilized stained glass, incorporating both biblical subjects and images of royalty. The flexibility of lead allowed for the creation of complex patterns and for the many small pieces of glass to be held securely together, which is evident in the famous rose window from the Chartres Cathedral.