Replacement Glass for Historic Prismatic Transoms
Whether a project involves minor repairs or recreating an entire installation that had been removed and destroyed, work on historic transoms often requires replacement material. Zinc came is still commonly in use, and can be supplied by some of the same manufacturers that produced came a century ago. The ingredients of waterproofing grout, likewise, have changed little since the prism glass was first installed. Prismatic glass tiles, however, are harder to come by. There are generally three replacement options: custom cast new glass tiles, textured glass and salvaged historic material. Deciding which approach is most appropriate is dependent upon the amount of glass required, the degree of accuracy desired, and the project budget.
Several companies are capable of producing new pressed glass tiles. Some have historic molds bought from defunct prismatic glass companies; others use computer design software and laser cut graphite dies to create patterns that are identical to the historic material. Though this approach results in the most accurate reproduction material, the expense of custom casting may be prohibitive for smaller projects that require few tiles.
Textured, or patterned, glass is sheet glass upon which a pattern is rolled. Several patterns especially those with linear ridges (such as narrow reeded or ribbed glass) may be acceptable substitutions for original prism tiles. Textured glass can be ordered in sheets and cut into tiles in the glazing workshop. Advantages of textured glass over custom pressed tiles include the availability of sources, cheaper costs and virtually immediate availability.
Reputable specialty glass collectors and salvage companies may be a source for replacement historic prism tiles. The profusion of manufacturers and tile patterns once available limits the likelihood of locating an exact match. Those working with collectors should ensure that original materials on offer were not removed from existing installations purely for salvage and resale.
The color of the replacement glass may also have to be decided. Originally, prismatic tiles were clear. Until World War I, manganese was added to the process to decolorize the otherwise green glass. Decades of exposure to ultraviolet radiation, however, can cause a reaction in the manganese that then imparts a purple or pinkish tone to the glass. It may be possible to find patterned glass or salvaged tiles in a color that approximates that seen in solarized historic tiles. Exact matching is not likely, or necessarily desirable, considering the fact that the replacement material and the historic tiles would continue to change color at different rates. Because the historic tiles on the Hamm Building had not experienced significant solarization, the architects and transom contractor chose a clear patterned glass.
Possible Sources of Replacement Material
Architectural Glass, Inc., of Beacon, New York, can cast new prismatic tiles using historic steel molds purchased from an original manufacturer. (845) 733-4720
Rambusch Studios of Jersey City, New Jersey, sells original prismatic tiles acquired from the Canadian Luxfer Prism Company. Several patterns are available. (201) 333-2525
Pilkington/Libby-Owens-Ford, Toledo, Ohio, offers a 1/4" reeded glass that has been used as a substitute for historic prismatic tiles. (419) 246-6078
Hollander Glass Central, Inc., of Downers Grove, Illinois, manufactures cross reeded and double reeded textured glass that resemble prismatic tile patterns. (630) 629-7221
Please forward information on additional suppliers using the email link below.
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