Pigmented structural glass

File:Express Building.jpg

Black Vitrolite panelling on the Daily Express Building in Fleet Street, London.

Pigmented structural glass, also known generically as structural glass and as vitreous marble, and marketed under the names Carrara glass, Sani Onyx, and Vitrolite, among others, is a high-strength, colored glass. Developed in the United States in 1900, it was widely used around the world in the first half of the 20th century in Art Deco and Streamline Moderne buildings. It also found use as a material for signs, tables, and areas requiring a hygienic surface. Over time, the trademarked name "Vitrolite" became a generic term for the glass.

Overview

Pigmented structural glassTemplate:Efn was developed in 1900 in the United States by the Marrietta Manufacturing Company of Indianapolis, Indiana.Template:SfnTemplate:SfnTemplate:Sfn The product was made by combining borax,Template:Sfn cryolite, kaolinite, manganese, silica,Template:Sfn feldspar,Template:Sfn and fluorspar.Template:SfnTemplate:Efn The fluorides made the glass opaque.Template:Sfn

These materials were fused into glass at a temperature of Template:SfnTemplate:SfnTemplate:Sfn and then annealed.Template:SfnTemplate:Sfn The annealing process took much longer than it did for plate glass, often lasting three to five days.Template:Sfn This left the glass very strong, with a compressive strength about 40 percent greater than marble. If the product was to be affixed to another surface (such as the exterior of a building), one side of the slab was grooved before the glass hardened.

The exposed side(s) of the material was flame polished,Template:SfnTemplate:Sfn which left the product highly reflective and brilliant. Later manufacturing techniques used fine sand to polish the surface, followed by felt blocks and iron(III) oxide powder.Template:Sfn

Originally, only beige, black, and white colors were available. But by the 1930s, new manufacturing methods could make pigmented structure glass translucent, and more than 30 colors were available.Template:Sfn In time, even agate- and marble-like color patterns were available.Template:Sfn Black structural glass was sometimes silvered, to give it a reflective finish.Template:Sfn

Pigmented structural glass could be manufactured in flat panels or curves, and in a wide range of sizes and thicknesses.Template:Sfn Small mosaic tiles, affixed to flexible fabric, were another option for fitting the product to curved surfaces.Template:Sfn In time, manufacturers learned that pigmented structural glass could be carved, cut, inlaid, laminated, sandblasted, and sculpted to create a wide range of finishes and textures. When translucent, it could be illuminated from within.Template:Sfn

Manufacturing history

File:Eglinton Station Vitrolite.jpg

Vitrolite tiling at Eglinton station in Toronto.

Pigmented structural glass was originally marketed under the name "Sani Onyx" by Marrietta Manufacturing.Template:SfnTemplate:Sfn The company also used the name "Sani Rox",Template:Sfn while the term "vitreous marble" was coined by the firm as a general descriptive.Template:Sfn By 1906, the Pittsburgh Plate Glass Company had developed its own pigmented structural glass, which it called "Carrara glass".Template:SfnTemplate:Efn The same year, the Penn-American Plate Company began making a pigmented structural glass which it called "Novus Sanitary Structural Glass".Template:Sfn In 1916, The Vitrolite Company began manufacturing the product under the name "Vitrolite",Template:Sfn which eventually became a generic name for pigmented structural glass.Template:SfnTemplate:Efn In time, about eight American firms made pigmented structural glass,Template:Sfn although Carrara glass and Vitrolite dominated the market.Template:SfnTemplate:Sfn Names used by these and other companies to market the product included "Argentine", "Glastone", "Marbrunite", "Nuralite", and "Opalite".Template:Sfn Pigmented structural glass was also manufactured by Pilkington Brothers in the United Kingdom.Template:Sfn

Marrietta Manufacturing originally marketed pigmented structural glass as a lining for refrigerators. Industrial consumers quickly found new uses for the product as countertops, dados, bathroom partitions, storefront signs, and tabletops.Template:SfnTemplate:Sfn By the early 1920s, it was advertised as an inexpensive alternative to marble or ceramic tile. The Art Deco and Steamline Moderne architectural movements vastly increased the market for pigmented structural glass.Template:Sfn Its first important architectural use came in 1912, when it was used for bathroom stall partitions and dados in the Woolworth Building in New York City.Template:Sfn By 1929, of pigmented structural glass was being manufactured in the United States.Template:Sfn Throughout the 1930s, the product also found a use as cladding for storefronts, entryways, lobbies, and even as ceiling material. It was seen as an inexpensive means of making a dated building look modern.Template:SfnTemplate:Sfn

The Great Depression significantly reduced the demand for pigmented structural glass. American production reached only in 1933.Template:Sfn By the 1950s, changing architectural tastes had vastly reduced the demand for the product.Template:Sfn The last two American manufacturers ceased production about 1960: Libbey-Owens-Ford shut down its pigmented structural glass plant in 1958, followed by Pittsburgh Plate Glass in the early 1960s.Template:SfnTemplate:Efn Production continued in the United Kingdom until 1968, and in Bavaria, Germany, until the end of the 20th century.Template:Sfn

Characteristics

Unlike masonry, pigmented structural glass does not craze, swell, or warp. It is highly burn and stain resistant, and is colorfast. Since it is a glass, it is impervious to moisture.Template:Sfn It cannot absorb pathogenic bacteria, viruses, pathogenic fungi, or parasites, and is easy to render aseptic.Template:SfnTemplate:Sfn

References

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