Collectors’ Interest in U.S. Furniture Growing : Antiques: A New York company makes its purchases only after careful study of the piece it wants to buy.

In June, Harold Sack added a new page to consumer history when he became the first person to pay $12 million for an early American desk.

It was a very nice desk, an 18th-Century Nicholas Brown Newport desk and bookcase. Before too long, the New York dealer had sold it to an unidentified customer for an unidentified profit.

“We didn’t lose any money,” he says. “If it’s a great piece, we never pay too much. The only mistake comes if we’ve romanced the thing. If our analysis is correct, then we’ll go the distance and set new records. There’s always someone with knowledge and money and power who wants the best.”

Sack is one of the world’s foremost authorities on American furniture. He and his brothers run Israel Sack Inc., an antiques company in New York founded by their father. In his book “American Treasure Hunt,” Harold Sack tells how his father helped create and nurture a market for early American furniture almost single-handedly during the first half of the 20th Century. Today the Sack disciples include the White House, Winterthur Museum, the Metropolitan Museum of Art, Colonial Williamsburg and individuals ranging from Henry du Pont to Bill Cosby.

A national trustee for the Baltimore Museum of Art since 1981, Harold Sack was instrumental in setting up the first of the museum’s annual antiques shows. The show concentrated on affordable collecting and diverse collecting interests--as represented by 40 dealers--but the underlying purpose was to increase knowledge about antiques.

Sack says today’s collectors of early American furniture tend to be younger (30 to 50 years old) and to know more than in the past.

“Especially at those higher price levels, it’s important to know your potatoes,” he says. “It takes a lot of knowledge to have the courage to spend a lot of money.”

It also takes a certain amount of courage to treat a Nicholas Brown Newport desk as if it were just one of the family.

“All our customers use their antiques. They don’t fence them off at all,” he says. “Even if they pay a quarter million dollars for a chair, they’ll use it. And so do their friends.”

He says Baltimore has a lot of hidden antique treasures, “untapped sources of furniture that have never gone outside the family.”

The Baltimore Museum of Art would love to see some of that furniture eventually find its way into its galleries. Its decorative arts collection includes American, English and Continental work with special strengths in Maryland furniture, English silver and ceramics of the 18th and 19th centuries.

(An exhibition devoted to recent accessions in the decorative arts coincides with the antiques show. Representing about a quarter of the museum’s acquisitions in this area during the past five years, the show includes examples of Federal furniture as well as other fine examples of 18th- and 19th-Century furniture, silver and glass.)

Half of the proceeds from the antiques show benefits Friends of the American Wing and Young Friends of the American Wing, primary fund-raisers for the museum’s decorative arts acquisitions.

But few museums can afford the sort of desks that Sack is able to buy.

“We’re trying to build on our strengths and fill in some gaps,” says Wendy Cooper, curator of the Decorative Arts collection. “We’ve been buying American glass, maybe a piece a year, because it is affordable and because we feel we could make it a strength without the kind of expenditures that furniture takes.”

So far, the market for American furniture has been American. The publicity generated by high prices, however, may begin to stimulate interest abroad, Sack says. He was recently interviewed by a Japanese magazine about the merits of American furniture.

“It’s foolish to say that American furniture is better than French furniture or English furniture,” he says. “American furniture relies on architectural proportion, line and form. Embellishment is secondary. Those pieces that are great were made by the artist craftsmen of big city centers for the wealthy merchant families who had no other place to put their money except possessions. . . . There was a climate, a relationship, that resulted in great pieces, each with a personality. Individualism in American furniture is what excites people too.”