Paris of the 1860s had a sparkling allure to those wishing to lead a freer and less conventional life and consequently many American students of art made their escape and landed on the banks of Europe's most bohemian capital. Paris, the home of Degas, Monet and Manet, was seen as an inexhaustible fount of inspiration, sumptuously teaming with poets, artists, absinthe-drinkers, actresses all mingling in cafes, art studios and Salons. It was a whirlpool in which Impressionism, the new 'less finished' style, was just beginning to establish itself as an act of rebellion against the Academie des Beaux Arts and the more formal style and subject matter which it dictated.

Paris played host to many American artists, most notably John Singer Sargent and James Abbott McNeill Whistler. They arrived to soak up the atmosphere and to learn from the French. The fruits of their labour, starting from 1860 and spanning four decades, are displayed at The National Gallery.

The rebels of the French artistic world, the Impressionists exhibited their work in their own galleries or in the Salon des Refuses . To them, traditional art was inadequate to express the new complexities of modern life. The Americans were enchanted with Paris and its atmosphere. They were onlookers - not just of life but of art too, studying at the Ecole des Beaux-Arts and private studios. However, commissions were not frequent and as practice the students painted each other or executed self-portraits. This sort of self-documentation is an interesting introduction to the exhibition of their works. These portraits are loosely brushed but are not yet impressionistic. The portraits depict the haughtiness and dandyism of the models without concentrating too much on the realism and careful brushstroke then taught by the Academie.

For artists such as Whistler, the emphasis shifted from the importance of subject to colour and composition. The most famous painting in this exhibition is undoubtedly his Arrangement in Grey and Black, No. 1: Portrait of Artist's Mother. The painting is oppressive in the flatness of its composition and the monotony of its colour scheme. His mother's complete stillness- as if she is holding her breath- and the multiple shades of grey indicate a life stopped still by mourning. The only touch of colour is in her cheeks, suggesting that some zest for life remains in her yet. The painting did not gain instant acclaim and was almost rejected by the Royal Academy in London; opinions on it were divided in Paris. In 1891, twenty years after the painting was completed, it began to be discussed by the French critics as a masterpiece.

Other notable paintings in this exhibition are Sargent's contrasting full-length paintings of Mrs Henry White, wife of an American diplomat, decked out in respectable white, and the more scandalous Madame X (Madame Pierre Gautreau), a socialite from Louisiana. The latter caused some commotion in the Salon, which at the time was mostly visited by the Parisian middle class. It was not the revealing black dress that caused such controversy, but rather how it was worn. Sargent portrayed the boldness and sexiness of this upper-class woman, qualities which the middle-class could not imitate or afford.

'The hostile reception given to this painting when it was shown in 1884 effectively ended both Madame Gautreau's career as a professional beauty and Sargent's time in Paris,' says Kathleen Adler, curator of the show. Sargent quickly left for London where he continued to paint portraits of the upper classes, always keeping the painting of Madame X in his studio as its licentiousness attracted fashionable clients.

It seems that the Americans were so committed to immersing themselves in Parisian life that, according to one contemporary critic, they could 'almost out-French the French'. The pose of Thomas Hovenden, an Irish born artist from New York in his self-portrait is too deliberately bohemian. He squeezes in a dishevelled appearance, a cigarette, scattered French novels, an easel and even manages to hold a violin. The best part of the self portrait, however, is the artist's defeatist expression - as if he realises that the painting he is working on is no good after all. John White Alexander's painting In The Café shows a model in fashionable costume seated in front of a mirror in a café. Unlike Renoir's paintings where the hustle and bustle of café life is captured organically, the Americans couldn't quite grasp the fluid impression of life and more often than not were compelled to stage it.

The Americans did not try to disguise the fact that they wanted to emulate new emerging artistic trends of the French. Willard Metcalf painted The Poppy Field while on his visit to Giverny, the home of Monet and his family. The theme is familiar to us in Monet's paintings and Metcalf's version is a fair attempt. Sargent was a life-long friend of Monet and painted the artist while he was at work. It is a beguiling piece of history: one artist's creative moment captured by another. Theodore Butler married Monet's stepdaughter Suzanne Hoschede in 1892 and this is depicted by Theodore Robinson in The Wedding March. He lived next door to Monet and often came to him for advice. But despite the Americans' efforts to infiltrate the group, the French Impressionists did not fully accept them. The only American member was Mary Stevenson Cassatt who exhibited with them four times between 1879 and 1886.

On their return to the US, artists had to decide how to transform what they had learnt and what inspired them into something which would please the American audience. The last room is dedicated to the work executed after they left Paris. American Impressionism is not quite the real thing, for it was adjusted to please an audience that wanted to see a wholesome America and not the risqué and more daring subjects of French Impressionism.

'The development of American Impressionism shows a balance between knowledge of French Impressionism, the conservatism of most of the artists' training, and even more, the conservatism of most art buyers back home' says Kathleen Adler. In the works created after Paris, they try a little less to mask the influence of artists who had the biggest effect on them; in EC Tarbell's Across The Room, it is strikingly apparent that he could not distance himself from Edgar Degas' dancing girls.

This exhibition gives an insight into where American Impressionism was seeded, as well as what was then in vogue; from their moustaches or hats to the style of painting they chose to immolate. Whether in their new found style or the themes, colours or inspirations, the Americans 'always had Paris' to feed their artistic imaginations.

· Americans in Paris 1860-1900 is at the National Gallery, London WC2, from February 22 to May 21.

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