What’s On the Surface Does Matter: The Conservation of Applied Surface Decoration of Historic Stained Glass Windows Alyssa Grieco Submitted in partial fulfillment of the requirement for the degree Master of Science in Historic Preservation Graduate School of Architecture, Planning and Preservation Columbia University May 2014 2 Abstract What’s On the Surface Does Matter: The Conservation of Applied Surface Decoration of Historic Stained Glass Windows Alyssa Grieco Advisor: George Wheeler A stained glass window is both an architectural building element and an individual work of art. Like architecture, a stained glass window is composed of a variety of materials, mainly glass, lead, and surface decoration, each of which has its own conservation issues. Surface decoration, which includes vitreous glass paint, silver stain, and enamels, is the component of a stained glass window that is sometimes underappreciated. While it may not pose a major threat to the physical stability of the window or the safety of the window’s environment, it is the decoration that defines the windows as works of art, with imagery that holds the window’s history, including a direct view into the traditions, ideals, and beliefs of the people of their time. The conservation of the surface decoration of stained glass windows has never been fully analyzed, and both glazing and conservation professionals are constantly seeking information regarding the history of the materials and techniques used in order to create or restore a stained glass window. With conservation, the methods and techniques used to maintain and conserve the decoration will vary depending on a number of circumstances, including the location of the window, the history and traditions of the people involved, and the tools available to the conservators. As with all conservation fields, there are also ethical considerations to address in order to be sure that the authenticity of each work is maintained. For this history, it is also important to note the past restoration techniques used on these types of decoration, as well as what is being used today. This includes successes and failures, both of which bring essential information to the conservator. Each window brings with it an entirely new 3 history and set of decoration conservation problems so there are no universal solutions for this field. Stained glass is a fascinating field because it combines the worlds of art and architecture with a single object and the surface decoration plays an important role in this. By analyzing the history and techniques of these three surface decorations, it is possible to not only preserve an underappreciated element inherent to these historic stained glass windows, but also the overall aesthetic of true works of art that serve to enhance the buildings in which they reside. 4 Acknowledgements This thesis would have been impossible without the constant encouragement and advice from my advisor, George Wheeler, and my two readers, Drew Anderson and Julie Sloan. I am sincerely grateful for their guidance and endless support throughout this entire process. I would like to dedicate this thesis to my family and friends, who keep me calm and grounded while providing much needed love and support. A special thanks to my parents, who are always there for me and continuously remind me to never stop believing. Thank you for everything. Finally, I would like to thank my golden retriever, Briggs, who reminded me of the importance of taking a break every now and then. His companionship, often sitting across my lap, was a constant reminder of the love and support I have around me always. 5 Table of Contents I. Introduction ………………………………………………………………………………..p. 7 II. A History of Glass for Stained Glass Windows………………………………p. 18 III. Stained Glass Painting Techniques………………………………………………p. 52 IV. Vitreous Glass Paint……………………………………………………………………p. 96 V. Silver Stain…………………………………………………………………………………p. 121 VI. Enamels…………………………………………………………………………………….p. 130 VII. Conservation Principles and Ethics…………………………………………….p. 146 VIII. Conclusion…………………………………………………………………………………p. 194 IX. Bibliography………………………………………………………………………………p. 197 6 I. Introduction Illuminated by transmitted rather than reflected light, stained glass inspired a special sense of wonder and mystery that was rich in symbolism—heavenly light from the sun traversing matter to produce radiant images that evoke the mystery of creation and the passage of time as light rises and falls in a window over the course of each day.1 Timothy Potts, Director of The J. Paul Getty Museum Stained glass windows are not only a practical element to a building but each one is also a unique work of art. Similar to architecture but unlike many works of art, they comprise several different components and materials, all of which need individual attention and care. The three main components of a window are: (1) the glass; (2) the lead; and (3) the surface decoration. All three are integral to a stained glass window and therefore deserve equal attention when it comes to preservation. Decoration is the component of a stained glass window that is sometimes underappreciated. While it may not pose a threat to the physical stability of the window or the safety of the environment in which the window resides, the paint is essential to these windows as works of art. It is the imagery that they present that holds the majority of the history of the windows, including a direct view into the traditions, ideals, and beliefs of the people of their time. Without the imagery, most of the meaning behind these windows to the past would be lost. Unfortunately, much has already been lost; stained glass is considered by many in the conservation industry to be one of the most vulnerable of art forms2. The preservation of these windows is crucial to the retaining of valuable information and insights into the past. In terms of conservation, the methods and techniques used to maintain and conserve the paint will vary depending 1 Raguin, Virginia Chieffo. Stained Glass Radiant Art. 2013: 7. 2 Brown, Sarah. Glass-Painters. 1991: 4. 7 on a number of circumstances, including the location of the window, the history and traditions of the people involved, and the tools available to the conservators. As with all conservation fields, there are also ethical considerations to address in order to be sure that the authenticity of each work is maintained. It is important to note the previous techniques used as well as what is being used today; successes and failures are both important to understanding the nature of the materials with which one is working. Stained glass is a fascinating field because while the windows themselves are viewed as works of art, they are meant to be placed within an architectural setting thereby combining the worlds of art and architecture with a single object. By analyzing the history of glass painting, it will be possible to not only preserve an underappreciated element inherent to these historic stained glass windows, but also the overall aesthetic of true works of art that serve to enhance the buildings in which they reside. The Creation of a Stained Glass Window Before delving into the history of glass painting, it is important to understand these windows as a whole, including how the different elements interact with one another. Every stained glass window begins with a design that is then drawn as a cartoon, or an outline of the window’s design to be formed by the glass pieces and over which the glass is cut (Figures 1 and 2). Before the introduction of paper, it was usually drawn on a whitewashed table or plaster floor. 8 Figure 1. A medieval glazier’s table used for design outlines for stained glass. Image from Sarah Brown, Stained Glass: An Illustrated History. 1992: 18. Figure 2. An early 16th century cartoon and resulting stained glass panel. Image from Sarah Brown, Stained Glass: An Illustrated History. 1992: 23. 9 Often a charcoal drawing was done first and then the final one was fixed with ink. In the 14th century, parchment and paper were available for this purpose3. Accuracy was essential in this process because the final product fully depended on this drawing. The cartoons were typically very detailed and precisely organized, using a “color by numbers” system to show each artisan which shape was each color. In addition to this type of system, each piece of glass was usually given a letter or number that was either painted or scratched on the back; this made sure that no matter how many different people worked on a window, each piece would always end up in the correct location. These drawings were assets that were often handed down or reused. Cartoons were often reused for different projects but also for designs that were meant to be repetitive in a single project. On the other hand, there are also many ways to create several windows based on the same cartoon design. These techniques varied from changing details and altering inscriptions to reversing certain elements, moving the colors around, and changing painting styles. Therefore, one cartoon has a myriad of possibilities. Next, the glass needed to be cut. In the 12th century, glass cutting was done primarily with two tools: (1) a hot iron and (2) a notched iron bar called a grozer, which was a tool that leaves a “nibbled” edge. The iron tool was thicker at one end; this end was heated and then applied to the glass where it was to be cut. Water was then dropped onto the heated area in order to produce thermal shock. The result is a crack along the surface, which then allows for the glass to be easily broken by hand. The grozer is then used to chip away at the broken edges to create intricate shapes.