ETCHING is a little like skating, says Richard Wallace: ``The needle just glides across the ground.'' Mr. Wallace, a professor of art history at Wellesley College, is one of the organizers of a show now at the Boston Museum of Fine Arts. ``Italian Etchers of the Renaissance and Baroque'' is a groundbreaking show - literally. Etching involves breaking a ``ground'' - either acid-resistant wax or varnish - that has been applied to a copper plate. After the design is etched into the ground, the plate is immersed in acid.
The scratches left by the needle allow the acid to bite into the metal plate but not the surrounding area, still covered by the ground. When the acid has done its job - always a judgment call by the artist and never fully under his control - the plate is withdrawn, the coating removed, and the plate inked for printing.
Compared to engraving, a kindred graphic art that calls for a strong, sure hand behind the engraving tool, etching seems almost spontaneous.
Professor Wallace's skating metaphor is meant to convey the wobble and risk as well as the grace and glide: Etching is not that easy! But a good etching captures not only line but light. Wallace speaks poetically of ``sun dazzle'' and ``gauzy light.''
The 150 etchings in this exhibition were drawn from public and private collections in the United States and Europe. At the end of the High Renaissance in Italy, etching allowed artists to throw fresh light on old images, such as the Holy Family, or to probe the shadows of artistic personality.
Most etchings are modest in size, more intimate than paintings, says Wallace. One ``reads'' etchings, he says, emphasizing the intimacy of the bond between the beholder and the work of art.
``Looking'' is primary, agrees Sue Welsh Reed of the museum's print division, who, with Wallace, organized the show and wrote the catalog.
``This is not an exhibition that tries to answer questions,'' she says. Rather, it provides a survey of the variety and depth of the work done in etching at a turning point in Italian art after the High Renaissance of Raphael, whose paintings sometimes provided the originals for etchings.
First used around 1510, etching became a medium favored for recording and copying designs used in paintings, to try out ideas, to advertise concepts, and for a change of pace. In the flowing, supple etching of Parmigianino that opens the show, we see an early master combining the effects of painting and drawing in the portable, ``mass produced'' genre of etchings.
Ms. Reed organized the show both by region and time period. The 12 sections illustrate the influence of major artists (Claude Lorrain, Annibale Carracci) as well as larger trends. In the early years, the influence of the darker, more static engraving style fought with the more impulsive quality of drawing. The show illustrates how etching came into its own in the 17th century.
Reed included as much different subject matter as possible, as well some virtuoso drawings, a couple of the original plates, and free-standing glass cases displaying books using etchings for illustrations.
Reed's emphasis on variety is borne out by a tour through the show. Etchings depicting Christ Jesus healing the sick stand next to mythical allegories; atmospheric landscapes by Lorraine vie for our attention with a marvelous ``autobiographical composition'' by Castiglione depicting the artist as a classical river god.
An event staged by the Medici family in the Piazza Santa Croce, Florence, is rendered in astonishing detail by Jacques Callot. From another wall, classical ruins, painstakingly recorded, call to the viewer, and, in a not entirely successful experiment, Camillo Procaccini gives us ``The Transfiguration'' in which Jesus, towering over Peter, James, and John, dissolves into light - and broken lines.
Variety of theme compounds variety of treatment; the museumgoer finds himself returning for a second and third look. He learns to see and, seeing, to experience the refined, casual quality of the Renaissance etching. Somewhere between drawing and engraving as an art form, etching makes for a kind of visual ``happening.'' Wallace speaks of ``optical vibration'' caused by various kinds of lines.
The illustrations on this page indicate something of the range of aesthetic effect one confronts in the show. The linearity of bas-relief, the distance (and silence) of landscape, the explosive inward space of vision: The etching was a tool of the imagination just as was the 17th-century literary form of essay (essayer means to try something out) explored by Michel de Montaigne (1533-1592).
The ornamental panel (left) is by an artist known only by his monogram (seen in the top lefthand corner). As Reed says in her note to this plate, ``Visual pleasure can be derived from tracing the changing course of a line and the form it describes.'' The landscape by Mercati (bottom right) plays the ancient ruins off against the dreamlike reality of a contemporary buildings in the background. Castiglione's ``God Creating Adam'' (top right) is a monotype, a type in which an unworked plate covered with ink was rubbed by a wooden point. Castiglione invented the form and, says Reed, in this print succeeds in doing something unique. The hand of God, she points out, touches Adam with ``an almost electric dynamism.''
Wallace and Reed agree that the viewer is drawn close to the work and required to read between the lines. Much depends on the paper. But the museum's paper specialist, Elizabeth Lunning, warns against reading our enthusiasm for the paper back into an artists' experience.
In the early stages of preparing the show, Ms. Lunning visited the Florentine Archives. There she found Medici household account books; a ledger for every year provided her with plenty of examples.
With Reed, Lunning also visited a spot where fine-art papers have been made for 700 years. Fabriano is a small village at the foot of the mountains famed for the water used in paper manufacture. ``I was very moved to be on the spot'' where the original papers had been produced, says Lunning.
The side trip to Fabriano produced unexpected results. After a tour of the premises, the visitors chatted with the hostess, who became interested in the show. Eventually, Fabriano became a key sponsor.
In the Renaissance, Fabriano made papers for etchers included in the show. Four-hundred years later, Fabriano gave a generous discount on the paper used in the Boston catalog.
Catalog designer Carl Zahn says that, in the 33 years he has spent designing catalogs for the museum, this paper stands out. The feel, or ``hand,'' of the paper used in the catalog is what the Renaissance artists would have been used to. Being handmade, the paper has ``imperfections,'' says Mr. Zahn, in color and density.
In the early stages of printing the catalog, it had to be carefully watched as it went through the press. The ``laid lines'' or ribbing is part of the paper, not added. The translucency of handmade paper can cause problems when dark images are printed on both sides of one page. Paper of this quality, Zahn explained, is used by fine printers when they have only a few hundred copies to see through the press. The museum printed 4,500.
The unique marriage of subject and medium, along with detailed and surprisingly readable text, tasteful design and great care in production make the catalog symbolic of the show as a whole.
In no other art is the paper so important, says Henri Zerner of Harvard University, an expert on prints. Etchings are difficult to appreciate, but the variety and breadth of this show allows us ``to get into it.''
Mr. Zerner qualified his enthusiastic praise, adding that the show is ``a bit recondite.'' Unlike most museum shows, it's not built around a well-known master - a Rembrandt, a D"urer, a Goya. (The museum has previously mounted shows on all three.) Zerner says that, given the variety, the show ``tends to even out artists'': ``Schiavone could have been better represented,'' for example.
But these are quibbles, he hastens to add: ``Italian Etchers of the Renaissance and Baroque'' offers the public a unique way of discovering an aspect of the world of prints. At a time when paintings and drawings are commanding incredible sums, Wallace adds, etchings are still within the reach of most collectors. This show, with its catalog, affords a superb introduction to a neglected art.
The exhibition will remain on view in Boston until April 2. After that, it will move on to the Cleveland Museum of Art (April 25-June 25) and, finally, the National Gallery of Art in Washington, D.C. (Sept. 24-Nov. 26).