Replacement of Damaged/Missing Glass Panels

Production of pigmented structural glass in the United States ceased several years ago, and only in rare cases have inventories been discovered. Yet, checking all the obvious and not so obvious sources for replacement may prove to be rewarding. Occasionally, long established "jobbers" will have a limited supply of pigmented structural glass. It is not uncommon for glass contractors to buy entire stocks of glass when companies or supply houses go out of business and to use this original material to make repairs on historic buildings.

Locating a source for new glass similar to the historic pigmented structural glass is as much of a problem as finding the original glass. Until about 10 years ago, glass companies near Bavaria in Western Germany were producing a pigmented structural glass called "Detopak." At present, these factories appear to be the only suppliers in the world. The glass is made in small batches, and the color can vary due to the lack of modern mechanization in the pigmenting process. For this reason, American importers generally only deal in white and black glass.

If a satisfactory replacement panel cannot be located, one alternative is to remove a piece of glass from an inconspicuous part of the building and position it on the more prominent facade. Modern spandrel glass, a new substitute material described below, may be considered as a replacement for the less visible area.

Substitute Material for Damaged/Missing Glass Panels

If replacement glass cannot be found to replace broken or missing panels, a compatible substitute material may be considered if it conveys the same visual appearance as the historic material, i.e., color, size, and reflectivity. Two of the historic producers of pigmented structural glass now manufacture a similar product known generically as "spandrel glass" and marketed under the trade names of Spandrelite and Vitrolux. This heavy plate glass has a ceramic frit or colored ceramic surface fired to the back of the glass. Stock colors are available in a range of grays, browns, bronzes, and black. Custom colors are also available.

A second option simulates the appearance of pigmented structural glass by spraying paint, carefully tinted to match the historic glass, onto the back of plate glass. However, the paint may fade over a long period of time and thus require periodic reapplication.

Sheet plastics may also be used and are available in a range of colors, sizes, and thicknesses. These materials are more suitable for interior applications, however, where the negative effects of ultra-violet light are lessened.

Conclusion

The preservation of pigmented structural glass remains more a materials issue than a detailing problem. The glass panels were and are extremely susceptible to breakage due to accident or vandalism. In addition, many of the historic installation materials such as the mastic adhesive and joint cement did not possess a long lifespan. Periodic maintenance, inspection, careful repair, and selective replacement--in like kind--are essential for the longevity of any historic pigmented structural glass veneer.

Even though the architectural glass industry has continued to expand its production of different types of glazing, the imaginative innovations of Carrara Glass, Sani Onyx, and Vitrolite in the early part of this century have not been surpassed. New technology, combined with human artistry, produced exteriors and interiors alive with color and dimension. Glittering movie palaces, sparkling restaurants, and streamlined storefronts as well as the more mundane kitchens, restrooms, and laboratories exemplified the extensive variety and potential of pigmented structural glass. Carrara Glass, Sani Onyx, and Vitrolite were integrally linked to the architecture and interior design of the 1930s and 1940s and helped to define what was "modern." Thus, every effort should be made to preserve this significant historic material in both the innovative buildings of the Art Deco, Streamline, and Moderne styles as well as the "modernization" of earlier structures.