THE DIFFERENCE between Art Deco and Modern is the difference between feast and famine, between fat and lean, between apulence and austerity, between the '20s and the '30s.

Art Deco was the last whoopee of the aristocratic, prosperous and peaceful turn of the century. Modern was the lean line of the Depression, world war and the revolution of the proletariat. Modern is a Marcel Breuer's tubular steel chair. Art Deco is a squashy, overstuffed velvet chair.

The importance of Breuer in the history of interior design is definitively explained in "Marcel Breuer, Furniture and Interiors," the exhibit that opens Tuesday and continues through Nov. 22 at the Baltimore Museum of Art.

The show, organized at the Museum of Modern Art in New York, was directed by Stewart Johnson, MOMA's design curator, and Christopher Wilk, who wrote the accompanying book -- with an important introduction by Johnson that puts Breuer in his place.

The 1928 steel-and-chrome Cesca chair (named after Breuer's daughter) is in almost every breakfast room today, as the Thonet chair was in every cafe at the turn of the century. Breuer's first chair, now called the Wassily chair -- a lounge chair designed in 1925 -- was the first tubular-steel furniture made. It was the most innovative furniture design since Thonet's bentwood mass-production chairs.

Breuer in his later years was uncomfortable about the chairs, as though they were a youthful and frivolous indiscretion.

He preferred to talk about what he thought of as his serious work: the big commercial buildings such as the I.B.M. Research Center or the Torin (Conn.) office buildings and factories; or the Hubert Humphrey Health, Education and Welfare building and the Housing and Urban Development headquarters (both in Washington).

Ironically, many critics today believe that Breuer will be remembered not for his big designs but for his little ones -- his houses more than his skyscrapers, his chairs more than his prefabricated concrete window pane.

Breuer, the last of the Bauhaus building blocks -- those designers and architects who, with Cranbrook School of Art, brought us Modern -- died at 79 on July 1, just before his retrospective opened at the Museum of Modern Art (though he lived long enough to contribute to the research and to know about the show).

The exhibit covers more than the past half-century. Advent of Modern

In his introduction, Johnson, for once and for all, sorts out the two prevailing styles of that period: "The year 1925 was a watershed in the history of Twentieth-Century design because of two events: one public, spectacular, much heralded; the other private, though not unnoticed and ultimately of more far-reaching significance."

The public event was the Exposition Internationale des Arts Decoratifs et Industriels in Paris, which gave its name to what we now call Art Deco.

The private event was Breuer's design of the first tubular-steel furniture, marking the advent of Modern furniture design. Before then, there was little or no furniture specifically designed for Modern interiors.

Johnson explains: "Art Deco, despite its occassional use of brilliant colors and eccentric forms, was essentially conservative, based on a neo-classicism that combined more often than not the weighty, symmetrical forms of Louis Philippe with the elegant surface decoration of Louis XVI: garlands of flowers, swags of drapery, nymphs and graceful animals.

"It was aimed accurately at the haute bourgeoise and the rich new industrialists, who could be expected to admire the quality of its workmanship and the opulence of its materials while being reassured by its references to a highly decorous past."

Johnson says that though the style persisted for 15 more years, 1925 was its high-water mark. Actually there are manifestations of it until the early '50s.

The flip side of the mid-'20s was Modernism. The style goes back to the 19th century. Johnson believes that Joseph Paxton's Crystal Palace in London, the first World's Fair exhibit hall, may be the grandfather of the style. Adolf Loos in Vienna railed against ornament before World War I. Walter Gropius' Fagus Shoe Works was built in 1911. But Bauhaus, which has come to be the lightening rod of the style, was organized in Weimar, Germany, just after World War I, and in 1925 moved to Dessau in buildings designed by Walter Gropius.

Breuer was the youngest of the earnest men and a few women who went to Dessau to save the world through purity of design. He was the only one of them born in the 20th century (1902), almost 20 years younger than Gropius, the founder of the school. But by 1925, Breuer, first a student, became the master of the furniture workshop.It was there that he developed the steel-framed furniture that was his real contribution to design.

Shifting Interiors

The real surprises in the Breuer exhibition are the pictures showing the evolution of interior design from the starkness of the late '20s to the warm, cozy, contemporary cottages in the late '30s and '40s.

In the Erwin Piscator apartment in Berlin (1927) everything is stark, pared down to the essentials. A few glass objects, including a coffeepot, are the only ornaments sitting on the wall-hung, glass front cabinet. Breuer's 1926 tubular-steel chairs sit at what looks like a drafting table.

The dining room for the Laszlo Moholy-Nagy house at Bauhaus shows a wall of built-in cabinets (a novelty in those days), a remarkable round table and a strange flying-saucer lamp. But here the starkness is not so harsh. A painting, doubtless Moholy's, brightens the effect. It's difficult now, with only black-and-white photographs to study, to tell the color scheme. Wilk says that Moholy chose the colors and suspects they were the bright, primary colors beloved at the Bauhaus.

In 1931, Breuer had slipped from his institutional purity to allow oriental rugs and vases of flowers in the Boroschek apartment in Berlin. The chairs here are the 1928 cantilevers, but the cabinet is still wall hung. In his room for a woman at the 1930s Paris Exposition, the desk with papers and telephone points out the emergence of the executive woman. The simple tubular-steel bed is certainly not for a sybarite.

Breuer's bedroom for the Ventris flat (1936) has the cane-and-steel Cesca cantilevered chair and wood furniture as well, but the floodlight lighting fixture would do credit to today's highest tech look. Breurer's use of lighting is neglected in the exhibition. In one early photograph, he uses an assembled form of track lighting.

Mellowing Out

A drastic change comes between these Early European apartments and the ones he designed with Gropius in America. His own house in Lincoln, Mass. (1939), is shown with wood bookcases (sadly empty), upholstered Isokan lounge chair, curtains and Venetian blinds, even wall-to-wall carpeting.

By 1945, Breuer had mellowed considerably, some say in reaction to the traditional northeastern American houses. One wonders if it were not also because of the influence of Frank Lloyd Wright. In any case, a house he designed in Lawrence, N.Y., for the Geller family shows a wall of stone, a window wall with fixed louvers, wall-to-wall carpenting. The cutout plywood furniture was designed for this house.He called the floor plan, "binuclear," and arranged the house into two zones, connected by the entry. One was the public area, "living, eating and visitors"; the other for "concentration, work and sleeping."

The dining room of his house designed for the garden of the Museum of Modern Art shows a sloping wood ceiling (a Breuer trademark), more books and color used on a splendid storage wall. The doors of the wall slide so that glass and china can be stored on the upper level, food passed through at the counter height. The living room used his Isokan lounge chair.

His own houses become progressively richer in textures, colors, patterns, though they are never soft houses. None of the furnishings has that marshmellow softness characteristic of Art Deco seating so popular now. Many have stone floors or grass mats. Eventually Breuer gave up on stone fireplaces for bushhammered concrete, perhaps because of the cost of stone. The houses lost a lot of friendliness with the change.

Some of his later houses, with Herbert Beckhard, have monumental granite tables and counters that certainly would handicap the person who likes to move around furniture.

Around the Bend

The story of how he designed his first bent tubular chair is one of Modernism's best legends. Breuer, at 23, was less excited by his job than by learning to ride his first bicyle, the freedom of movement it gave him, the opportunity to see the sites in Dessau.

The bicycle's tubular steel, bent to shape frame and handlebars, recalled Thonet furniture -- wood bent to shape chair backs and legs. Breuer thought that tubular steel would be equally light and stronger as a furniture material.

Wilk says Breuer went to the Adler company, makers of his bicycle, and suggested tubular-steel furniture, but they weren't interested. Then Breuer went to Mannessmann Steelworks, which invented seamless extruded steel tubing, and bought lengths the same diameter as the tubes of his bicycle (20 millimeters), which were bent to his specifications. Then he hired a plumber to weld the tubes together. Wilk says Breuer was first interested in aluminum, but it was more difficult to weld and more expensive than steel.

In spring and summer of 1925, Breuer, with some help, made the first version of what came to be called the Wassily chair (after Wassily Kandinsky, a painter and friend who admired the chair greatly). Because of the welded joints, his first version was stiff, without much bounce. Lucia Moholy, without asking Breuer, photographed the prototype and it was published. Though he had many inquiries about the chair and made and sold them in his own workshop, he was uptight about it. He wrote:

"It is my most extreme work both in its outward appearance and in the use of materials; it is the least artistic, the most logical, the least 'cosy' and the most mechanical."

The chair, as described by Wilk, was "constructed of nine pieces of steel tubing, bent and bolted together, the nuts and screws visibly extending beyond the tubes . . . A crucial difference between Breuer's chair and other Modernists' , however, . . . is the sense the chair gives of the seat and back being suspended above the ground -- or, more correctly, floating within a network of lines and planes. The sitter never touches the steel framework of the chair. The notion of suspending the sitter in pure space remained a constant one."

A Bauhaus film strip of 1926, published in the Bauhaus magazine, showed the evolution of the chair and predicted that "In the end we will sit on resilient air columns."

Planes & Frames

Breuer's furniture, according to Johnson, aroused "instant recognition among architects and designers that bent tubular steel was the ideal material for Modernist furniture . . . As soon as the news got round, other designers seem to have decided that they too should try tubular steel . . . It seemed to have everything. Furniture made of tubular steel was strong, lightweight, easily portable, and inexpensive to produce, since it required little of the handcraftmanship of conventional wood construction. And -- in some ways even more appealing -- it looked new; not only was it machine-made, it looked machine-made. The cool austerity, the sleek gleam of metal were exactly what had been needed to bring the Modernist interior to life."

The principal difference between the Moderns and their predecessors, Johnson points out, was that earlier designers were concerned with mass, the Modernists with volume. Like Harry Bertoia's great side chairs in 1952, space flows through and around the Breuer's planes and frames. Mies van der Rohe and Lilly Reich's cantilever side chair (1926), the chair and other pieces for the Barcelona Pavilion date from 1927, after Breuer's breakthrough. Le Corbusier's first experiments in tubular steel started in 1927 as well, though he had used metal pipe for legs and a stair rail in 1925 in his Pavillon de l'Espit Nouveau.

The Cesca Chair

Breuer's most famous chair, the so-called Cesca chair, was not, according to Wilk's evidence (after a long search through court files), the first cantilever chair. Mart Stam, another designer, claims that invention in late 1926 or 1927. Breuer claims he was working on such a chair when Stam visited him in 1926. The design was also claimed by Anton Lorenz, who filed suits against almost all Modern designers for years on the basis of owning Stam's copyright as well as his own design registration for a cantilevered chair. Lorenz is credited with the later design of the Barca Lounge.

But in any case, Thonet began to sell Breuer's version in 1929. Breuer's use of a wood-framed cane seat and back looked like the familiar Thonet bentwood designs, then being revived. This easing of the stiff formality of steel furniture helped contribute to the Cesca chair's popularity.

With the problems of the lawsuit, Breuer's chair wasn't sold in this country until 1960, though by then, many variations and copies, especially those as breakfast room chairs, had been made and sold. Wilk said at the MOMA's opening that Breuer, "who should have become a billionaire from the designs, really earned very little from it, only small commissions from Knoll and Thonet."

Other Breuer designs shown in the exhibit are interesting. The tables look rather shaky and flimsy, though the 1929 three-wheeled tea cart is a charming design. Breuer later added a fourth wheel, so maybe it wasn't that practical at first.

The later lounge chairs -- the steel-and-rattan model of 1928-29 suspended on coiled springs, and its steel-and-canvas variation -- are both handsome. An aluminum-and-wood lounge chair, rescued from the Breuer's garage, has been refurbished for the show. His use of divider walls and hanging cabinets and shelves were other innovations.

Among the show's happiest finds were furniture brought by a family who had commissioned a Breuer house in Berlin. They escaped Berlin with all their furniture. They lent the desk, which took three men half a day to put back together, and the cart.

New Home, New Work

After the Nazis closed the Bauhaus in 1933, Gropius immigrated to England. Wilk says that Breuer was not as pressured by the Nazis -- Breuer, after all, was Hungarian -- but was persuaded to go to England by the opportunties for work. He arrived in 1935.

Breuer's first project was a plywood version of his aluminum long chair, called the Isokon long chair -- a handsome, curvilinear design reminescent of some of the Thonet chaises and rocking chairs. Breuer's other plywood furniture, tables and chairs are mostly bad copies of Alvar Aalto. His only interesting furniture after Isokon is the cutout plywood furniture of 1945 (which unfortunately tends to fall apart), a very handsome desk with cantilevered drawer units, and his monumental granite dining tables and counters.

Breuer came to the United States in 1937 to teach at Harvard and work in an architectural partnership with Gropius. They designed many handsome houses in the style that we now call "contemporary." In 1942 he set up his own office, largely dealing with institutional and commercial buildings.

As was Wilk's recent book on Thonet, and Johnson's on Eileen Gray, the show and the book are exhaustively researched, well thought out and presented. The earlier Thonet and Gray books, and MOMA's Gray exhibit, have resulted in a revival of Gray's designs and some of Thonet's earlier pieces. This show may be expected to do the same for Breuer.

Breuer's Cesca and Wassily chairs are authentically produced by Knoll International, Stendig, and others. The Door Store, Ursell's, Bon Marche, Scan, Design Store, Conran's and most other furniture and department stores carry either the Knoll, the Stendig or variations by other manufacturers.

The Baltimore Museum plans a Marcel Breuer Day on Thursday (Oct. 15) with lectures and tours of a 1959 Breuer house owned by Mrs. Arthur U. Hooper and the Bryn Mawr lower school. Tickets are $8 for nonmembers. For information call (301) 396-7101.