Reproduction of 16 century stained glass doorways.

By the mid-16th century, window glass was increasingly common.
 But even for the wealthy, it was still a luxury: upper-class houses still only had glass in the windows of the most important rooms; by the end of the century, the nicest middle-class homes had glass in about half their windows. And for those aristocrats who spent months in each of their various estates, their window glass was such a precious commodity that they had it taken out and stored carefully in their absence.

A few photos of the process of making.