FAR BELOW THE stacks and card catalogues in the basement caverns of the Library of Congress, Robert Espinosa and Tom Albro stand bent over antique-looking wooden machines, automated only by the touch of their own hands. Clad in wrap-around blue smocks, they work long hours at preserving rare books and a rare craft, bookbinding.

Bookbinding is as old as 600 A.D. The art is now being revived, but not many craftsmen choose this demanding art.

Since 1971, the Library of Congress has operated a conservation shop where their collection is maintained in tiptop condition and where their rare books are painstakingly repaired by Espinosa, Albro and four other staffers. Newton's "Philosophiae Naturalis Principia Mathematica," Jefferson's copy of "Lectures on Rhetoric" by John Adams, as well as Martin Luther King's family Bible are among the books they have restored and rebound.

According to Robert Espinosa, from the time the original library was founded in 1800 by Thomas Jefferson, John Adams and James Madison, until the reorganization of the convservation department by restoration officer Peter Waters 10 years ago, all conservation binding was done by the Government Printing Office.

"We're what you might call 'the new era,'" notes Espinosa. "Today our restoration-conservation shop is divided into two departments: paper conservation, run by a staff of 17, and our department, rare-book conservation."

Rare-book conservation is the more specialized of the two departments. It takes longer to learn. Few bookbinders are qualified for this delicate work.

Recently, Espinosa and Albro held a bookbinding workshop at the library (sponsored by the library's American Folklife Center), demonstrating the many complex skills involved in the process.

The process can be broken down into five stages: sewing the pages, end-banding, page-trimming, covering and tooling. Originally each stage was done by separate individuals. Today, most bookbinders master all these skills.

The pages are sewn on a wooden frame. For this particular demonstration five columns of double-thickness Irish linen thread are used to attach the 50 pages, also made of Irish linen. "A 50-page book takes about one hour," says Espinosa. "It's the most time-consuming stage of the entire process."

The threads hang from metal screws at the top of the frame. The pages are laced together from the bottom of the frame with a curved needle, often using the original holes, if they're not damaged.

"You have to be careful to distribute the tension evenly," says Albro. "The pages must be sewn firmly, but leaving room for some flexibility so the book opens easily." Sometimes following the sewing, a gelatine adhesive (easily removed) is sparingly spread along the spine to secure the threads. "I'm sure you've seen books that almost need to be peeled open -- particularly books from Europe. These are examples of sloppily sewn and overly glued spines," notes Albro, almost haughtily -- you know he wouldn't tolerate such a thing.

The next step is attaching the end bands -- the small cord of leather that is attached to the top and bottom of the spine. Albro demonstrates this step, placing the sewn pages into a wooden press, leaving only the spine exposed. He then sets about meticulously sewing the leather band to the spine with French silk thread. It's used as a support and for decorative purposes," points out Albro. The fancier the leather piece the more elaborate the spine becomes -- often a braided band is used or colorful threads added. "Before making the band too elaborate," warns Albro, "be sure the pages are strong enough to support it."

Attaching the cover is the third step. Espinosa takes a pre-cut rectangular piece of deep red leather (cut a little larger than the book) and "wets it out" -- working a salt solution, potassium lactate, into the leather. "This makes the leather more maleable and prevents the paste from drying out or soaking through the leather," says Espinosa.

Next he brushes a starch paste made of rice on the underside of a piece of Nigerian leather. "Goat-calf- and pigskins are all leathers that can be used in covering books. Here at the library we prefer the native goatskin leather from Nigeria -- similar to the leather used to baseballs. It's better for conservation since the Nigerians don't treat the leather with sulfuric acid as we do here in the U.S.," notes Espinosa.

Espinosa recommends taking off all rings and bracelets when working with leather. "We wear wrap-around smocks with no buttons to avoid marking up the covers," he says. He also suggests using a felt base to work on."

Espinsoa likes rice paste since "it is more tacky and adheres better than wheat [paste]." The leather is left to set awhile to absorb the paste.

Once the leather is ready, Espinosa wraps it tightly around the cardboard covers of the book, working the leather downward from the spine. The corners -- a skill unto themselves -- are next. Espinosa cuts the leather diagonally at each corner and neatly folds them inward. He works the corners into rounded points, alternately using the heel of his hand and then his fingers ("two of the most important tools in bookbinding," he say).

For the final step in attaching the cover, Espinosa fits the leather into the top and bottom of the spine, tucking it gently beneath the end bands. The book is now ready for the binding or finishing press. Here, the book is placed in another wooden press, protected from scratches with felt. Uniform pressure is applied with a series of threads that are stretched across the spine, firmly sticking down the leather cover and making decorative spine indentations. The book is usually left in this press for a 24-hour period.

In the fourth step of trimming, the book is placed in a plough press with the rough edges exposed. A movable cutting edge, or plough, is then run back and forth across the page edges, evening them out. The book is then turned over and the top and bottom edges are cut. The plough press the Library of Congress now has was donated by Vernon Clapp.

"In the old days, books bought in Europe often had uncut pages. These books were considered more valuable, because they were pristine, untouched, but also unread," says Espinosa.

The most fascinating part of the demonstration is Albro's tooling of the spine. The trimmed, covered book is once more placed in a press. Albro painstakingly spreads a small square of gold leaf on a cushion. He cuts it with a dull knife into 10 tiny strips. He removes a long-handled brass tool, called a pallet, from an electrically heated anvil, lightly dabbing it on a water-soaked cotton pad. Quickly, he touches one of the gold-leaf slices with the pallet. He pickes up the gold and presses it onto one of the spine indentations in a single motion. He also shows how to decorate the cover with a narrow column design, using a tool called a roller. The roller's wheel attachments provide an endless variety of designs.

"For the longest time, we had no idea what it [the roller] was," laughs Albro. "It just sat in the workshop until someone who'd seen something similar in West Germany told us what it was used for."

Several courses on bookbinding are offered in the metropolitan area as well as bookbinding services.

Tom Albro holds bookbinding workshops throughout the year, usually teaching three or four students a year. "Because bookbinding is very much a one-on-one learning process, handed down from teacher to student through the years, I only take on a few pupils at a time." He can be reached at the conservation shop, 287-5437.

Linda Blaser will teach "The Fine Art of Bookbinding" starting April 14, 7 p.m. Sponsored by the Smithsonian Residents program, the course meets Tuesdays through June 2 and costs $78 for members, $99 for nonmembers. Call 357-3030 for details.

Bookbinder Nancy Garuba, Hobart Street in Mt. Pleasant, will offer her next eight-week workshop the week of March 29. Fee: $130. Garuba, who used to work at the Library of Congress' conservation department until last summer, now has her own bookbinding studio, where she not only teaches but will take books for rebinding.

"The cost for a rebinding job depends on the length of the book and how long it takes me. The price can range from $50 to $300. Right now I could probably do a bookbinding job within three weeks, but around Christmas time I have about a two-month backlog."

Conservateur Frank Mowery of the Floger Library, 201 E. Capitol St. SE, will be offering 8-to-10-week sessions in bookbinding beginning "sometime in May--following our move into the new facility." Mowery also does free-lance bookbinding evenings and weekends. Prices range, he says, from a small job -- ($30) -- to a fine bookbinding job, which can run into the thousands of dollars.

Book-Makers, 2025 I St. NW (where the Library of Congress purchases much of its conservation equipment) specializes in the restoration of old books. Owner August Velletri says they will do simpler binding jobs too, as well as make up a new book. The price of a bookbinding varies. Simple jobs cost $28 to $30. Depending on the job, the book takes one week to a month to complete. Velletri said he opened his shop following his retirement from the Foreign Service. "Bookbinding was a hobby of mine, but when I returned to it I discovered the materials were nearly impossible to find, so I opened up my own place."

The Writer's Center, at the Glen Echo Gallery, MacArthur Blvd. in Glen Echo, is holding an exhibition entitled "Bookmaking: Book and Experimental Prints from the Writer's Center" now through March 23. Hours: Monday-Thursday, 10 a.m.-5 p.m.; Saturday and Sunday, noon-6 p.m. Call 229-0930 for details.

For good general information on bookbinding and conservation, consult the Abbey Newsletter printed bimonthly by Ellen McCrady.

The newsletter keeps readers informed as to what's happening nationwide in bookbinding and conservation. Cost: free trial issue and $12 for year's subscription. The newsletter can be obtained by writing: The Abbey Newsletter, 5410 85th Ave., Apt. 2, New Carrollton, Md. 20784