First, the craftsman would design the window on a full-scale drawing. Then, the individual pieces of glass were cut and shaped to fit the design. The pieces were then painted with enamel or stain and fired in a kiln to set the colors. Finally, the pieces were assembled and joined together with lead strips and soldered into place to form the completed window.
The most time-consuming part of the process was typically the painting and firing of the individual glass pieces. Some colors required multiple firings to achieve the desired intensity, and the process of cooling the glass after each firing had to be carefully controlled to avoid cracking or damage.
Overall, the creation of a stained glass window in the Middle Ages required a high level of skill and patience, and the time it took to complete a single window was a testament to the dedication and artistry of the craftsmen involved.