Stained Glass In Medieval Times

Margaux Ratcliff
The Evolution of Stained Glass in Medieval Times
MSE 1111
Fall 2017

Medieval stained glass windows are the main feature of many famous buildings, from the Augsburg Cathedral of Germany to the Sainte-Chapelle in France. Due to cultural significance alone, Medieval stained glass is an important topic to learn more about the culture of Europe during the Medieval Period. However, the study of stained glass has one more important advantage. Since Roman times, the process of creating glass has remained remarkably similar, especially in the composition of the glass itself and the usage of it. The medieval times spurred many transformations in the usage of glass and its manufacture. Demand for glass led to a new type of glass,
Glass production and stained glass making were independent of each other and most glass was imported [3]. Some of the glass used might have been recycled or produced by a similar method to the Romans, for medieval glass and Roman glass both had around 1.5% of potash, an oxide of potassium, and 1.5% of magnesia, an oxide of magnesium. If not recycled, the production of this soda glass required a relatively pure form of soda, and natron was most widely used to meet this requirement. The new glass being produced in the 6th century contained a much larger amount of potash and thus did not need as much natron. The reason for this change is most likely due to a shortage of the supply of natron, as the material was internationally traded and events such as the Justinian Plague would have significantly impacted supply. Other possible reasons for a switch in formulas include environmental changes, for a major cold period during the years 536-545 AD might have stopped soda lakes, such as the Wadi Natrun, from evaporating, impeding the formation of natron and leading to a shortage of the material [4]. This preliminary usage of a wood-ash based glass foreshadows the later switch of the stained glass industry to forest glass around the 9th century. During this time, glassmakers began to use an ash created from many locally-growing plants [3]. This new type of glass, composed of 2 parts
One technique was to add iron oxide pigment to the glass by painting it on, and then firing the glass in a furnace to fuse the paint to the surface of the glass [6]. A secondary technique discovered in the 14th century, called “silver stain,” involved painting a silver compound on the back of the glass and then firing the glass in a kiln [6]. This silver compound was usually composed of either silver sulphide or silver nitrate mixed with clay [9]. Contrary to its name, silver stain was used to color glass from “pale lemon” to a “deep orange” color [6]. Slightly after the end of the medieval times, the invention of silver stain had led to multiple different-colored enamels, and windows were able to be painted as if they were a true painting. For most of the duration of the medieval period, however, cames were a steady and constant aspect of stained glass windows, and any extra decoration was provided by black paint used to provide shading or outlines