By BRETT ZONGKER
Associated Press

WASHINGTON (AP) - Sixteen paintings by American artist Gilbert Stuart of some of the nation's founding fathers and other figures are showing their true colors for the first time in decades through a major conservation project at the National Gallery of Art.

The project is restoring the original appearance of Stuart's portraits of people including presidents George Washington and John Adams. Gallery conservators have been painstakingly removing yellowed varnish from Stuart's paintings to reveal true flesh tones and clothing colors that had been hidden by a discolored old protective coating.

Conservators told The Associated Press the work may reveal some new discoveries about Stuart's work. His "Vaughan-Sinclair" portrait of the nation's first president from 1795 may actually be a more finished painting from an earlier time than originally thought. It will likely draw interest from Stuart researchers, they said.

In a portrait of Abigail Adams that took Stuart 15 years to complete, conservators believe they discovered traces of an original headdress that was changed later, perhaps to better match the changing fashions by the time the painting was completed in 1815.

"What's emerged now that time's varnish is gone is everything we knew to be true and more," said Nancy Anderson, a curator of American and British painting. "You get to see the virtuoso technique because nothing's obscuring it anymore."

The conservation project spans some of Stuart's earliest paintings to portraits he completed late in life as one of the most famous portraitist artists. The gallery holds 42 paintings by Stuart altogether. He is most famous for his paintings of Washington, particularly the full-length "Lansdowne" portrait of the president.

Stuart was born in Rhode Island in 1755 and trained with a Scottish portrait painter. At 19 during the start of the American Revolution, Stuart went to London and worked as an assistant to artist Benjamin West and later moved to Dublin to continue painting and perfecting his technique. He returned to the United States in 1793 with his sights set on painting Washington and making a name for himself.

Supreme Court Chief Justice John Jay wrote a letter introducing Stuart to Washington to help the artist gain access to the president. Stuart had a list of subscribers clamoring for a depiction of the nation's most famous politician and military figure. Eventually, Washington agreed to sit for Stuart in Philadelphia.

Stuart painted three portraits while Washington was sitting. One bust-length portrait he supposedly didn't like and rubbed out _ but copied it several times before destroying it. One of Stuart's original copies is believed to be the "Vaughan-Sinclair" portrait that has been conserved, said portrait conservator Joanna Dunn.

She uses a mild solvent to remove the varnish with tiny cotton swabs to treat the paintings. Old restoration paint that no longer matches the original color also is removed. Damaged areas can be repaired with in-painting using a tiny brush filling in the losses of pigment to show the works as the artist intended. One of Stuart's paintings of his uncle, Capt. Joseph Anthony, has a severe tear Dunn is working to cover.

The most dramatic change as conservators demonstrate the process comes as the aged varnish is removed. The yellow layer has hidden Stuart's brushwork for decades since they came to the National Gallery of Art from private collections. The varnish also changes the color relationships in the paintings, making them look flatter.

"A painting is really like a trick of the eye," Dunn said. "It's a two-dimensional thing that's making it look three dimensional. So when you change those color relationships, you lose the depth of the painting."

Bright white collars have been restored, along with a glimmer of blue in John Adams' eyes and the details of Washington's face _ the pink in his cheeks and his five o'clock shadow.

"Prior to cleaning, he was quite jaundice," Anderson said. "Now beautifully fresh, and you can see the life in his cheeks, the blood beneath his skin instead of just the yellow varnish. He has just emerged transformed by the treatment."

The conservation treatment also indirectly extends the life of the paintings, Dunn said. If the varnish isn't removed soon enough, it may never come off. Conservators would reach a point where removing the varnish also would remove the paint. And when the paintings become too discolored, they are rarely shown to the public because they are less attractive.

Treatment of Stuart's portrait of Abigail Adams revealed the style of her head gear changed from the time he started the painting in 1800 to its completion in 1815. He started with a much larger bonnet but covered it up and replaced it with a more stylish headdress later.