Today, glass is again all the rage in architecture. This is partly to do with innovations in glassmaking that have given us new qualities of transparency and opacity, reflectiveness, and color. Such architects as Jean Nouvel and Herzog & de Meuron revel in the expressive potential of new forms of glass.

But the present glassiness also is an homage to the cool glass architecture of early Modernism, when vitreous façades were new — and genuinely excited the public. Call it “Mad Men” chic.

The first glass-curtain-wall skyscraper in Manhattan was the United Nations Secretariat Building, on First Avenue at 42nd Street, completed in 1950.

In 1952, Lever House, designed by Gordon Bunshaft of Skidmore, Owings & Merrill, opened at the northwest corner of Park Avenue and 53rd Street. It was the first glass-curtain-wall office building set in the heart of the main business center of the city, on a Park Avenue that still exclusively comprised masonry buildings.

To the public, Lever was “the eighth wonder of the world,” as the architecture critic, cultural commentator, and social critic Lewis Mumford wrote. People thronged to view it. It was something entirely new, exciting, and modern. Mumford (1895-1990) noted the open forecourt, the glistening marble, the beds of flowers, the stainless-steel columns, the greenish-blue windows, the bluish-green spandrels — and the weeping-willow tree. And he judged that the public was, basically, right:

Lever House is a building of outstanding qualities, mechanical, aesthetic, human, and it breaks with traditional office buildings in two remarkable respects — it has been designed not for maximum rentability but for maximum efficiency in the dispatch of business, and it has used to the full all the means now available for making a building comfortable, gracious, and handsome.

Lever Brothers, the British soap manufacturers (Dove, Lifebuoy, Pond’s, etc.), liked the idea of a glass building because by constant cleaning it could be made to gleam, and so to symbolize the company’s products.

In the 19th century, Lever Brothers made a great success of Sunlight soap. William Lever (Lord Leverhulme) grew concerned about working-class living conditions, and created a model town, Port Sunlight, for Lever Brothers workers in Merseyside. Heavily influenced by the Arts and Crafts movement, the picturesque village inspired Ebenezer Howard, the leader of the garden city movement and founder of Letchworth Garden City in Hertfordshire. Lever provided financial backing to Howard and others to popularize the garden city concept.

Mumford’s thinking owed much to Ebenezer Howard, and thus indirectly to Lever Brothers. In Greater New York, the “garden city aesthetic,” if not the socialistic ideals, notably influenced Forest Hills Gardens. But perhaps the purest implementation of the ideal came at Sunnyside Gardens, in Queens, where Mumford and his family resided between 1927 and 1936.

Something of the garden city spirit informs most of Mumford’s architectural judgments. He noted, for example, in his review of Lever House, that Ebenezer Howard had, at the beginning of the 20th century, envisioned garden cities’ commercial centers as comprising crystalline glass buildings.

But unlike the countless glass-curtain-wall structures that ultimately not only ceased to excite but thoroughly dismayed most New Yorkers, Howard’s wouldn’t have been monuments to “maximum rentability” but exemplars of “maximum efficiency in the dispatch of business” and humane working conditions. At Lever House, Mumford noted, no desk was situated where it wasn’t bathed in natural light and didn’t enjoy inspiring views, the employee cafeteria was as elegant as any restaurant in the city, and the virtues of the outdoors were, in plaza and terrace, made integral to the design.

Lever Brothers rigged up an elaborate window-cleaning system to maintain that gleam. Unfortunately, “cost of good repair” is exceptionally high in Modernist architecture. Lever House wore down over the decades, but in recent years its painstaking restoration, courtesy of Aby Rosen and Michael Fuchs, has been an extraordinary triumph.

At the southwest corner of Fifth Avenue and 43rd Street stands the former Manufacturers Trust Co. branch, now JPMorgan Chase, from 1954, also by Gordon Bunshaft. Here, in Fifth Avenue’s first glass edifice, wrote Mumford, was a structure that revived “the dream of building a whole city of glass that haunted the Victorian imagination.”

Mumford was no cheerleader for glass. He knew that context meant everything, and one of the achievements of the bank’s architects was recognizing what could be done in the sheltered setting their building would occupy, nestled in the L-shaped space made by 500 Fifth Ave., at 42nd Street, and 4 W. 43rd St., mitigating effects of wind and the sun’s heat.

Mumford called it a “crystal lantern,” noting that the glass box was especially delightful by night, aglow from within. He also loved, as did everyone, the gigantic vault, designed by Henry Dreyfuss, placed not in the bank’s deep recesses, but right in the front window.

The bank was, said Mumford, “as complete a fusion of rational thinking and humane imagination as we are capable of producing today.”

The great architectural historian Nikolaus Pevsner went one better: “Here is perfection, and, as is the fate of classic achievement, it cannot last long — the Italian High Renaissance less than twenty years, from Leonardo’s ‘Last Supper’ to about 1515.”

Well, Manufacturers Trust’s moment didn’t last long. But was it ever perfection?

fmorrone@nysun.com