CZECHOSLOVAKIAN glass sculptor Vaclav Cigler writes a glass: "It is matter, yet it denies matter. As transparent as water, as clear as air. Both illusion and reality, true to it and misleading. It can reflect back shattered images of our visual experience. . . . It is the reflection of man. In its essence it has equally the properties of matter and spirit."

Cigler is one of three master Czechoslovakian sculptors -- along with Rene Roubicek and Vera Liskova -- showing 36 or so pieces of art glass at the Fendrick Gallery, 3059 M St. NW, through July 3. A companion exhibit shows the work of Miluse Roubickova-Kytkova, another Czech glass sculptor. The show is one of the most beautiful exhibits ever mounted in this city.

Glass at its best is a way of seducing light, of giving permanent form to the fantastic worlds you see transmuted in drops of rain dew or tears. It is the genius of Cigler and Liskova that their best works could only have been made of glass.

The three Czech glass sculptors each have a different approach. Their work is not all alike, except that all of the objects seem to be maquettes for huge architectural pieces. Indeed, the artists are fond of having the objects photographed against the landscape to make them seem monumental. Unfortunately, commissions for large glass sculpture are scarce.

Liskova's piece called "Menuet ," is the absolute essence of glass, and one of the most beautiful objects I have ever seen. Thin icicles are pulled into soaring pinnacles of light. Another, "Joy" (composed of bubbles, growing out of each other), is also lovely.

Vera Liskova's work with Lobmeyer, the well-known Viennese (and once Czech) glass company, has been recognized in the United States since she was included in a Museum of Modern Art Show in 1950. In 1966, she began to melt the harder chemical glass piping (similar to Pyrex) over oxygen flame. tIt seems blasphemous to like her work to anything, because its pure abstraction could be made only from glass, and only through her surprising technique. Still her work has all the fascination of a free-soaring fountain.

Cigler's work has only the capture of light in common with Liskova. The most striking may well be the simplest, a thick circle of optic glass. Look carefully through it, because it is a window into a world that may forever haunt you. Each one of his other 16 pieces slices optic glass in a different way, to make rainbows, to mirror the surroundings, to create optical illusions of stripes and patterns. It you move an inch, each work changes completely.

Cigler, in the catalogue, writes that he sees glass as a mediator for observation and meditation.

Roubicek won the Grand Prix of Expo 1958 in Brussels, and was honored for his 14-by-10 foot glass cloud at Expo 1970 in Osaka. He used hand-shaped crystal rods for these wonderful, exuberant architectural pieces filled with much movement, light and life. Roubicek's newer work is much quieter and, to me, less interesting. He makes people shapes, sculpted from hollow glass, that unfortunately remind some people of the legendary "schmoo."

Roubickova-Kytkova's charming glass flower sculptures may well be the most popular works in the exhibit. Liskova's glass animals are only amusing.

Meda Mladek, Washington art historian and with her husband J. V. Mladek, the country's greatest patron of Czechoslovakian art, organized the Fendrick show and wrote and paid for the accompanying catalogue.

Roubicek and Liskova were also in the Renwick Gallery show "New Glass."

Mladek points out that the three glass sculptors were all born in the '20s and graduated from the Prague Academy of Applied Arts, Painters found work illustrating books, making posters, restoring frescoes in old convents and castles and designing theater costumes and sets for the film industry.

Sculptors went into the applied arts. Glassmaking, because of Czechoslovakia's long history of glass supremacy, attracted many young sculptors to design utility glass. The best started to explore glass as an artistic medium, at the same time that Americans were experimenting in the United States' great studio glass workshops.

Washington is becoming one of the best places in the country to see art glass. The "New Glass" show and earlier exhibits at the Renwick Gallery, encouraged many commercial galleries to show art glass.

The Branch Gallery at the Tiffanee Tree, 1063 Wisconsin Ave. NW, specializes in glass with three-week shows of glass (and clay) artists. Its current (through June 22) glass show stars Randy Sewell and Richard Ritter.

Branch Gallery's previous show of William Morris' blown glass vessels and Michael Pavlik's concentric layers of blown glass, cut and polished were especially interesting. Pavlik, born in Czechoslovakia, escaped to the United States in 1965.

Branch also carries less expensive production glass. Greenwood Gallery, 2014 P St. NW, often shows glass. Seraph Gallery has had such success with glass that Anne Smith, Seraph's co-owner, is opening, with Sarah Eveleth, the Glass Gallery at 4931 Elm Street in Bethesda next month. Many other Washington galleries show American studio glass. American glassblowers are credited with reviving and currently leading the whole art-glass movement.

Art glass begins about $600 and goes up steeply thereafter. One Cigler work is about $7700. It isn't much to pay for some of the finest art of the late 20th century.