Note 271 — Chapter XVIII · (XXXII.)

For the most part this description, with the exception of the part about scaling-off glass in order to introduce a variety in colour, corresponds closely with the technical directions which Theophilus gives so fully and clearly in his Schedula Diversarum Artium of about 1100 A.D. It is pretty clear that Vasari is telling us here what he learned from William of Marcillat who would have inherited the traditions of the great French glass-painters of the thirteenth century.