After years of bewailing the disintegration of historic records, librarians and archivists say they are beginning to see progress toward preservation of documents ranging from the Declaration of Independence to fashion sketches from the 1920s.

"I think it's beginning to come of age after all these years of talking about it," Peter Sparks, director of the national preservation program of the Library of Congress, said after a three-day conference on statewide preservation programs that ended Friday at the library.The National Endowment for the Humanities says it has been estimated that more than 80 million volumes in American research libraries and more than 2.5 billion pages in state archives are in danger of being lost because of the paper's acid content.

Most book paper manufactured since the middle of the 19th century has a high acid content, which helps prevent the ink from running but also makes the pages turn brittle. In less than 100 years, they fall apart.

Custodians of books and records have been concerned about the problem for years but often have had trouble getting state and federal money to deal with it.

"State legislators are interested in potholes, they are interested in environmental problems, they are interested in nuclear waste sites," said Carolyn Morrow, Sparks' deputy. "It is not that they don't care about history, but they sometimes have to be educated as to why the rec-ords are important."

Apparently, the message is getting through.

In 1987, for example, the New York Legislature provided $500,000 to assist libraries, historical societies, archives and similar agencies preserve books, manuscripts, photographs, maps and other material.

One grant went to New York's Fashion Institute of Technology to treat its collection of 5,568 pencil, ink and watercolor drawings done by anonymous studio artists from 1915 to 1929. They were dismounted from brittle paper, mended, labeled and stored in acid-free folders and boxes.

Other grants went to preserve such items as farmers' account books and tavern records from the 19th century, a Fordham University collection including orderly books of George Washington, the Juilliard School's collection of early and first editions of the compositions of Franz Liszt, records of the black history of Smithtown, N.Y., and a Yeshiva University collection detailing the history of three organizations that helped Jews in two world wars.

Among other states with active programs are California, Connecticut, Illinois, Maine, New Jersey, South Carolina, Utah, Virginia and Wisconsin, Morrow said.

Meanwhile, Congress has increased funds for the National Endowment for the Humanities' Office of Preservation from $4.5 million in fiscal year 1988 to $12.3 million for the current fiscal year, which began last Oct. 1. The office supports cooperative microfilming projects and preservation of collections.

The National Historical Publications and Records Commission, the grant-making body of the National Archives, has a current appropriation of about $4 million and has funded more than 100 projects to develop government archives and records management programs in states, counties and cities.

"We have had a very, very good record on this in Congress this past year," despite deficit-cutting pressures to keep spending down, Sparks said.

The National Archives also has installed an imaging system designed to monitor the condition of the Declaration of Independence, the Constitution, the Bill of Rights and other basic documents. An Archives fact sheet distributed at the conference said the system takes pictures so precise that comparisons over time will detect the subtlest changes in a document.

Meanwhile the Library of Congress expects to be finished in a month or two with a program at a Houston pilot plant on technology to remove acid from books.

"The technologies are starting to come up, and people are starting to get into the mode for buying them, and pretty soon we're going to be doing it," Sparks said.