Mount Vernon, the famous home of George and Martha Washington, is taking on a different look. Its rooms are being returned to the way the interior of the mansion appeared in 1799, the year of George Washington's death.
Some visitors who know the historic house well have registered surprise and sometimes dismay about the changes that have taken place. They liked Mount Vernon the way they remembered it, despite the fact that over the years it had become embellished with Victorian-era overdressing and made even more comfortable and cluttered by latter-day decorating influences.
More recently, the interiors of Mount Vernon, along with those of Monticello, home of Thomas Jefferson, and the Governor's Mansion in Colonial Williamsburg, have been ''reinterpreted'' on scientifically based guidelines.
The Washingtons, it is now known, didn't use lots of furniture. Curator Christine Meadows explains that the west parlor was simply furnished with a sofa , one table, and 11 chairs. Rooms were generally rather sparsely furnished. ''The Washingtons needed lots of floor space to accommodate their frequent visitors who came with families, servants, and many trunks,'' she explains.
The floors in the mansion, it has been discovered, were bare pine boards. And the colors on the walls were far bolder and more pungent than the creams and soft pastels that have decorated the walls in recent years.
''We have overwhelming documentation on Mount Vernon,'' explains Miss Meadows , who has been curator since 1960. With the mansion furnishings committee, she has been responsible for the presentation of the furnishings in the house and for their authentication.
''We have not one, but two, inventories of the house,'' she says, ''one done after General Washington's death, and the second prepared after Martha Washington passed on a few years later.''
And, she notes, since Washington probably saved every scrap of paper he ever wrote, ''We also have much of his correspondence with his farm managers and his overseers during the years he was away, his orders for goods from England, and all his surviving diaries. These all give us a pretty good insight as to what the house looked like.''
Until recently nobody thought to examine a chip of paint under a microscope. Using new sophisticated paint-analysis techniques, Matthew Mosca, architectural conservator, has uncovered Mount Vernon's original color scheme. He had to work his way down through 20 to 22 layers of paint to arrive at the true 18th-century colors the Washingtons chose. These have now been restored to the walls of the mansion, including the bright, intense Prussian blue on the walls of the dow/stairs bedroom and west parlor.
Mr. Mosca began wozk on the $90,000 paint restoration xr/ject in December 1979. According to Historic Preservation magazine, his research has ''turned previously held notions of Colonial color schemes and decoration on their ear. . . . Despite the limited number of pigments available in 18th-century America, Mount Vernon, it turns out, was a veritable rainbow: vivid blues, lemon yellows, undulating greens, and bright copper.''
Washington seems to have had a particular preference for green, a color he found ''grateful to the eye'' and not likely to fade. The colors were replaced with the same materials and techniques used in the 18th century. Eighteen rooms have been completed, and work has begun on the two third-floor bedrooms.
The Mount Vernon Ladies' Association, which owns, preserves, and manages the estate, has committed itself to having all the rooms reflect the appearance they had when George Washington lived here.
''We are going to be as pure as possible with what we have,'' Miss Meadows says. ''This means that, besides the very different appearance of the paint, the rooms are now being dressed down and the furnishings adjusted. The floors have been stripped of the stain and wax put on in the 19th century.''
But by no means does the curator mean to imply that Mount Vernon now has all its original furniture. ''We estimate,'' she says, ''that we now have about 13 percent of the original furnishings. Another 13 percent are so close to being authentic that we could say they are so. Everything else is 'of the period,' and we have to make our own deductions. If an inventory calls for a dressing table in one bedroom, I have no idea what the original dressing table looked like. So right now we are substituting a Philadelphia lowboy in that place.
''There is nothing at all static about Mount Vernon,'' the curator continues. ''I believe it will be changing and being refined for another 100 years, as things come to light. The original contents of the house were widely scattered between 1799 and the acquisition of the property by the Mount Vernon Ladies' Association in 1858. So we never know when something is going to turn up.''
''Because many of the family portraits that hung on the walls are now owned by leading museums,'' Miss Meadows says, ''we have secured copies of six of the most important. These are hanging in their original locations. Charles Willson Peale, Robert Edge Pinne, and John Wollaston were the original artists. It would be impossible to convey the appearance of the rooms without the portraits, so we are fortunate to have the copies.''
''It always surprises me,'' Miss Meadow confesses, ''that there is this continuous fascination with George Washington and where he lived. Most people feel very possessive of him and of his home. To them, it is a precious shrine. And although a majority of our 1 million visitors a year are not connoisseurs of the decorative arts, they want to know exactly which pieces were original to the house, where Washington sat, where he slept, what he ate from, and what everyday objects he handled.''
Miss Meadows's own fascination with George and Martha Washington continues unabated. ''For 23 years I have concentrated on their domestic lives here at Mount Vernon, and I do fret a lot about their house,'' she says. ''I just hope this more authentic restoration now being completed will give people a better understanding of how the house functioned and how they really lived. After all my study and research, the Washingtons are by now old friends, although I must admit that I feel much more comfortable with Martha than with George. After all this time, he still seems awesome to me, with his great dignity and reserve and his remarkable consistency.''
Recent engineering studies have disclosed the need for major capital improvements, and a $10 million Mount Vernon Capital Campaign is under way. This fund will help preserve original structures, replace major utilities, modernize security and fire systems, finance a new Research Center and a conservation laboratory, and provide an endowment for the property.
Tax-free contributions can be made to John A. Castellani, Resident Director, The Mount Vernon Ladies' Association, Mount Vernon, Va. 22121. The association has always drawn its support from the private sector, gate receipts, and museum shop sales, but inflation and new needs have made the campaign for funds necessary. No government support has ever been received.
Last month the admission charge went up from $3 to $4. Mount Vernon is open every day in the year, from 9 a.m. to 4 p.m. in the winter, and until 5 p.m. after March 1. Feb. 22 marks the 251st anniversary of George Washington's birth.