New York — Your grandmother left you a painting with the admonition, ''Take good care of it, because it is valuable.'' But how valuable? You know nothing about the artist, and you aren't keen about the subject. You think you might like to give it to the Salvation Army. But would you be giving away a major or even a minor masterpiece? If someone offered to buy the painting from you, would you know a fair price to ask for it?
These are a few of the questions that owners of art objects wonder about, particularly if they live in small towns or remote areas of the country where there are few experts to consult.
A couple of years ago, Carol Prisant and her son, Barden, of Roslyn, N.Y., decided they could offer a useful service: a telephone system called Telepraisal , over which they could provide helpful information from an extensive computer data bank that they would keep up to date and from an extensive research library. The data bank includes auction prices over the last five years for 49, 700 artists.
''We have it easy in New York, with all our auction galleries, museums, appraisers, and dealers,'' Mrs. Prisant explains. ''But information can get pretty sparse after you cross the Hudson River.''
Since they opened their service in October 1982, this mother-son team has had over 2,200 customers call their toll-free number (800-645-6002), and they have answered inquiries about 5,000 paintings, drawings, prints, and pieces of sculpture.
Mrs. Prisant, who had been an antiques dealer since 1965 and is also a member of the Appraisers Association of America, was amazed one evening to hear her son muse that there ought to be some kind of telephone service that could give quick information about a specific artist and the current market value of his work.
It was spring 1982, and Barden was just graduating from Yale University with a degree in art history, considerable computer skills, a few basic business courses, and the immediate prospect of becoming an unemployed art historian. He opted instead for combining his talents with those of his mother and opening Telepraisal.
The Prisants proceeded to feed into their computer names and prices garnered from such prime sources as the Sotheby Parke Bernet, Christie's, and Phillips auction galleries in New York and London, William Doyle in New York, top-flight galleries in Paris and Amsterdam, and leading smaller auction galleries in the United States.
The younger Prisant explains: ''If there are no auction records, we consult our biographical sources, which contain information on more than 300,000 artists dating back to the 15th century. We carry on a dialogue with our clients, explain the art world, and refer them to potential purchasers if they want to sell their art. Sometimes we ask to see photographs of the work. If we determine that a work is of potential importance, we can refer clients to the specialists in the appropriate field (museum curators or independent experts) who can aid them in establishing its importance and authenticity.''
''The art world was leery of us, expressed skepticism, and acted as if we were treading on hallowed ground,'' Mrs. Prisant recalls. ''The public wasn't sure at first, either, and one man told us he didn't want some hotshot with a computer telling him what his stuff might be worth.''
In fact, the Appraisers Association of America has issued a press release condemning services like the Prisants', declaring that a bona fide appraisal implies ''a hands-on examination and that the object has been personally inspected, judged, and evaluated by the appraiser who signs the appraisal document.''
''We ourselves use a computer as a data bank in order to supply information, '' says association executive director Victor Weiner. ''Computer auction records and computed sales results are valid and important tools that all appraisers take into consideration. And photographs provide a visual image and a record. But these cannot tell you about the uniqueness, quality of workmanship, or authenticity of any given object. That can only be done by informed inspection.''
Mr. Weiner acknowledges, however, that such a service as the Prisants' could be useful in helping people avoid costly mistakes - particularly if clients consider it a preliminary indication of possible value and then seek the services of an appraisal expert.
David Nash, director of the Fine Arts Department at the Sotheby auction gallery in New York, notes: ''We have had quite a number of referrals from Telepraisal clients who wanted us to sell their art. . . . I think there are an awful lot of people who have a painting, or some other work of art, but not a clue as to where to go to get information about it. Such a service at least provides them with a place to start.''
In any case, the Prisants have persevered in their notion that they have something of value to offer. With each inquiry, they ask for the name of the artist, size of the work, the medium (such as oil on canvas, watercolor, pastel, and so forth), subject matter, and any date, inscriptions, or markings on the work's front or back.
They charge $30 a call (chargeable to major credit cards) if a data search yields information, $15 when a computer and library search turns up no information at all on an artist. One call can cover several paintings by the same artist.
Mr. Prisant likes to tell about the woman who telephoned about an Italian painting that she had on her wall. After learning that it could be worth as much as $500,000 she responded, ''Well, then I'm glad I moved it high on the wall so the cat couldn't get to it.''