A Vision for the Future: Stained Glass Conservation in the United States
Installation of environmental (isothermal) protective glazing at Trinity Church, Wall Street. This system required the stained glass to be set in the interior of the building using bronze frames and laminated glass set as the primary weather barrier.
By Brianne Van Vorst
Brianne Kozlowski completed an MA in Stained Glass Conservation and Cultural Heritage Management at the University of York in England. After graduating, she returned to her home state of New Jersey and worked for a private studio before opening her consulting firm, Liberty Stained Glass Conservation, in 2016. She recently concluded the conservation of the stained glass at Trinity Church, Wall Street with MBB Architects.
For many, stained glass often conjures images of the majestic cathedrals of Europe filled with walls of medieval glass. However, the United States has a long history of cutting-edge innovators in the artform, whose work is equally treasured. These include the talent and genius of designers like Louis Comfort Tiffany and John La Farge, whose work with opalescent glass influenced the international community. Frank Lloyd Wright and Louis Sullivan approached stained glass as architects, pointedly designing windows into buildings. Perhaps only in the United States can one find such avant-garde ingenuities as the incorporation of a piece of lunar rock into a stained glass window as at the Washington National Cathedral.
Before: Stained glass previously restored using mending leads through the face of the ox. After: Conservation repair using epoxy resin, eliminating the cumbersome mending lead.
Stained glass is a ubiquitous building element decorating structures ranging from places of worship to train stations to hospital waiting rooms. Historic stained glass reflects the materials and craftsmanship employed by the original artist to capture their vision. Treatment to prolong its life and functionality is often a visible and vital part of a preservation or adaptive reuse project. However, there is not an overarching philosophical or ethical foundation guiding the treatment of stained glass in the United States, nor is there formal education or a regulating organization to provide support to practitioners. This deficit shapes the direction of preservation projects and impacts the longevity and authenticity of the stained glass and of the building.
The absence of formal education specifically for the restoration or conservation of historic stained glass windows is a significant issue. There is a difference between those who design new windows (artists) and those who treat historic ones (conservators). Programs are available that teach the basics of fabrication and design, but they do not impart the philosophical, ethical, technical or framework of treatment options necessary to conservation. Building Arts or Objects Conservation programs that do teach philosophy and ethics merely touch on stained glass as one of many objects within a larger curriculum. Without formal programs it is difficult to measure the health of the craft with such datum as how many young people may be entering into the trade, thus contributing to the reputation of stained glass as a “dying art.”
The lack of formalized education assures that the only way to access knowledge and gain hands-on experience is through apprenticeships. The United States has several very old, continuously operated stained glass studios as well as newer outfits. Each studio has individual histories, objectives, styles, and experiences that naturally influence the methods taught. Their methodologies vary and may be guided by differing knowledge regarding the trade. There are many wonderful, talented and ethical stained glass studios that do their best to educate themselves and their apprentices. However, an apprenticeship taught in the vacuum of a specific firm’s objectives does not replace formal, unbiased education.
Identifying quality resources is also problematic. Several documents have been written by trade organizations, individuals, and the United States government which intend to articulate the appropriate approach to caring for stained glass windows.[1] Each document claims to be the national standard and it is difficult to summarize the scope of these documents due to their diversity. Some go beyond ethical discussions to explaining specific repair techniques. This obfuscates that each window and setting is unique and overlooks the critical fact that approaches are not always transferable between projects. These contradictions make it difficult for a client to identify which approach and practitioner are appropriate for their situation.
Unavailable historic glass matched through plating multiple pieces to achieve the correct color.
In cases where historic fabric is missing, new glass is infilled. Modern glass, paint and stain is carefully matched to the existing.
Aside from the lack of formalized education in the field, stained glass conservation does not have an authoritative governing body in the United States. We have an enthusiastic community in membership-based trade organizations that cater to both artists and conservators, none of which are specific to conservation. Their conferences are useful for networking and inter-professional support, but there are often very few lectures on conservation projects or practices. These conferences offer classes and workshops but without a continuing education system in place, their value cannot be quantified.
The state of stained glass conservation is similar to that of architecture before the establishment of the AIA, i.e., architecture firms operating according to various standards and objectives, without any outside validation of capability. Establishing the AIA as the preeminent professional body elevated the architect by lobbying for professional expectations through licensing, certifications and continuing education. Continuing Education is integral when advances in science can change acceptable practice quickly and effectively.
The absence of a similar infrastructure in the American stained glass industry creates discrepancies felt by practitioners, architects and clients. The treatment standard chosen by an individual studio becomes the basis for subsequent condition assessment and treatment proposals. Clients frequently receive multiple proposals each describing approaches so different from one another that they cannot be compared or levelled without hiring a consultant to reissue construction documents. Architects tend to call on consultants when faced with this situation. However, individual building owners are often unaware of the existence of consultants and are forced to make a decision that will impact the future of their artwork without sufficient information. The task of researching methodology and contractors can be so daunting to an owner that necessary maintenance is deferred leading to further degradation and ultimately higher costs for the project.
These discrepancies make determining scope, managing client expectations and simplifying the bidding process challenging for architects. The following are important points and clarifications any architect should keep in mind for a project containing the treatment of historic stained glass:
1. The terms ‘restoration’ and ‘conservation’ are two separate approaches, and the words are not interchangeable. Restoration is to restore something back to a previous period. In stained glass that tends to mean the period of when it was originally fabricated. Conservation is to conserve what is existing now with an emphasis on retaining existing material rather than trying to fully eliminate the appearance of age. It is possible to maintain a conservative approach respecting the integrity of original workmanship and material while making a positive aesthetic impact. Using epoxy resin or silicone to bond original broken pieces back together would be an example of conservation. Restoration would be to replace the broken piece.
2. The idea that certain windows deserve special treatment based on their age or perceived worth is incorrect and inherently dangerous. This appropriation is meant to recognize exemplary windows and ensure their proper care, but it is counterintuitive. It inevitability permits a lower standard of work if a decision is made that a window is “pedestrian.” An assessment of value, and therefore level of respect, is often left to the discretion of an individual. This is problematic because the concept of value changes over time and can be subjective. If a window is deemed to be not particularly valuable, a less measured approach may be employed. In the future, if attitudes shift and that window is understood to be valuable, the previous intervention may have potentially irreversibly changed or damaged the window. All stained glass windows deserve a measured treatment approach based on assessment of their condition. Perceived value is irrelevant.
3. Restoration or Conservation does not necessarily dictate cost or environment. To be clear: conservation is not intrinsically more expensive, nor does it only exist in museum settings. Conservation can fit within budget and in any environment when approached correctly.
4. Protective Glazing is a great option, when used appropriately. Windows have a characteristic that most other art forms do not – they also need to function. Modern changes to building code and increased demands of sustainability put additional pressure on stained glass windows, a traditional building methodology, to perform to modern standards. This pressure tends to culminate in the addition of a secondary glazing layer, known as protective glazing (PG). PG has been proved to be a valuable preventative conservation technique in many international studies, but its impact on building performance needs to be studied on a per building basis. There are various types of protective glazing, differing in material and type of ventilation. The options and their impact on the stained glass and the envelope need to be carefully considered and understood when designing a protective glazing system.
The chancel window of Trinity Church, Wall Street (1845).
These clarifications are in line with the Guidelines for the Conservation and Restoration of Stained Glass; produced by the Corpus Vitrearum Medi Aevi (CVMA). Internationally (outside of the US), this document is the accepted philosophical and ethical protocol used to guide the scope of treatment of stained glass. Similar to the Secretary of Interior’s various guidelines, the CVMA Guidelines provide philosophical rather than technical guidance. They identify stained glass as an art object of which we are stewards, preserving it for future generations. Enduring concepts such as an emphasis on research and documentation, repair over replacement, reversibility of treatment, and the value of preventative conservation prevail. Decades of scientific studies support the effectiveness of the CVMA Guidelines. As a result of this research, the document is the professional standard for stained glass conservators and it is supported within professional organizations, in scholarship & grant opportunities, and is taught at the world’s only stained glass conservation graduate programs; the University of York and the University of Erfurt.
The discussion of the current stained glass conservation climate is not intended to undermine the progressive and careful work of talented conservation studios in the US. The goal is to illustrate that the field is at a crucial moment where it is necessary to transition from a building trade to a professional discipline. As my field works towards a similar path of professionalization that architecture once required, there is an important supporting and uplifting role architects can play to enhance the care of our treasured stained glass heritage. Please consider this essay when you next meet a project containing stained glass, and the positive implications that the measured approach of the CVMA Guidelines may bring to your project specifications. Specifying this clear standard will provide guidance and set expectations for owners and those that work in the care of our existing buildings. Let us ensure the future of American stained glass for future generations.
The CVMA Guidelines can be found here https:/corpusvitrearum.us/conservation-organizations/
[1] The most well-known documents are The Stained Glass Association of America, Standards and Guidelines for the Preservation of Stained (and Leaded) Glass Windows, 2012 and Department of the Interior, Preservation Brief #33 but there are several others available.