THIS BLOCK SHOWS A LOT OF GLASS

Glass block used in a Streamline Moderne home, circa 1930:
As a residential style, it didn't catch on with Americans.

Glass block had its heyday in the Streamline Moderne architecture of the late 1930s, when architects were enchanted by its sleek lines and ability to form curves. After World War II, though, glass block suffered a steep decline in popularity—so much so that the big U.S. glass manufacturers such as Corning and PPG quit producing it altogether.  The last remaining dribble of glass block sales was given away to European glassmakers.

During the Eighties, however, glass block made a huge comeback. Hardly a month went by that some architecture magazine didn’t have a house with acres of glass block on the cover, and the U.S. glass companies once again cranked up their glass block production lines.

Glass block varieties. Note that many are special-order items.

Why did glass block disappear after the war? And why is it back?

Glass block first gained widespread popularity in Europe during the early 1900s. Originally used for factory windows, it was soon adopted in commercial and residential architecture as well. Its appeal among European architects only grew during the postwar rebuilding of Europe. In America, however, glass block didn’t really appear until well into the Art Deco period, and even then, it remained more popular in commercial rather than residential architecture.

Interesting glass block window
breaks out of the usual grid design.

One reason for this is that glass block didn’t really fit comfortably into any but the most radically modern U.S. home styles. It seemed jarringly foreign even in the most current homes styles of the era, such as the California Rancher.  Moreover, its unusual installation procedure was unfamiliar to most U.S. tract builders, who seemed to scrupulously avoid it.  Lastly, glass block’s effectiveness at diffusing light also turned out to be its biggest drawback: most U.S. homebuyers seemed to prefer windows they could see out of.

What brought glass block back to popularity almost fifty years later was, more than anything else, the huge self-indulgent master baths that came into vogue during the Eighties. With their giant whirlpool spas and showers, these rooms simultaneously demanded privacy and plenty of light, and glass block filled the bill perfectly. Of course, bathrooms have only gotten more pompous since then, so glass block is still very much a part of the luxury bathroom scene.

Bullnose end blocks provide a sleek edge.

It can be a standout material for countless other applications, though, including interior partitions, half-walls, columns, and of course windows of all shapes and sizes. Its modularity makes for almost limitless design potential—curves, stepped forms, and combinations of various block types and sizes are only a few possibilities.

Glass block’s ability to diffract light can be used to create spectacular effects. It's offered in 6x6, 4x8, 8x8, and 12x12-inch sizes and in a large range of face textures, from smooth to fluted to prismatic. Colored glass block is also available, although it usually must be special ordered. There's also a range of special blocks for creating square, chamfered, or bullnosed wall ends, as well as for forming curves of various radii.

 Radius blocks are available for tight curves:
larger radii can be accomplished with regular blocks.
(Courtesy Cincinnati Glass Block Co.)

Glass blocks are installed with mortar just like brick, and while they're very strong, they can’t be used to carry structural loads. Various accessories are available to provide uniform alignment, making installation a lot easer than in the past. However, like most masonry work, glass block is not a leading candidate for
DIY. I don't say this often, but this might be one job best left to a professional.