St. Patrick’s Cathedral in New York has a fine array of French, English, and American stained glass windows. Recently these windows were treated as part of a major restoration project. This was undertaken by cleanroom specialist company Vaisala, using digital equipment to help to monitor humidity and temperature conditions in the cathedral. This is essential for the long-term protection of art and artifacts.
The Cathedral of St. Patrick (or ‘St. Patrick’s Cathedral’) is a decorated Neo-Gothic-style Roman Catholic cathedral church located in the Manhattan region of New York City. The cathedral is the seat of the archbishop of the Roman Catholic Archdiocese of New York. The cathedral is located directly across the street from Rockefeller Center, facing the Atlas statue. Included within the set of beautiful stained glass windows are those found within the Lady Chapel. These stained-glass windows were manufactured between 1912 and 1930 by English stained glass artist and designer Paul Vincent Woodroffe.
The cathedral restoration project included the complete restoration of the interior and exterior of the marble building, a new central mechanical plant, new mechanical, electrical, and plumbing infrastructure, expansion of the Parish House, and renovation of private areas. Focusing on the stained glass windows, Arthur Femenella, President of New Jersey-based Femenella & Associates, led the international team of stained glass restoration experts. Key to this was the use of isothermal protective glazing to protect stained glass from vandalism, weather, and insidious condensation. This process also relieves the stained glass of its role as a climatic barrier.
The original glass is taken out of its existing position within the window and new protective glazing (clear glass) is set in its place. The stained glass is then framed in manganese bronze and reset in front of the new protective glazing. The ventilation space now created between the layers of glazing allows the air inside the building to fully circulate around the stained glass, which keeps the glass dry.
There are variations in the approach for isothermal glazing. The risk of getting this wrong could have led to major damage. For this reason the restoration team constructed six different models of protective glazing and installed each on the outside of a vertical window (the lancet) in order to determine which glazing models would perform best over a period of one year. This required the use of special digital monitors.
The monitors were developed by the company Vaisala, as part of their HUMICAP range. The monitors deployed were transmitters designed to actively monitor the interior, interspace, and exterior conditions of the six glazing models installed on the lancets. The probe structure was made of a solid material and the sensor was protected with a sintered Teflon filter, designed to provide maximum protection against liquid water, dust, and dirt.
The data was collected every 10 minutes, 24 hours a day. The analysis of the data allowed for the optimal design to be chosen and the restoration was completed successfully.
