Last Tuesday was particularly busy for Christie's auction house in London. During the day, the company disposed of 130 works from Charles Saatchi's collection of contemporary British art for a total of £1.6 million.

In the evening, Christie's held a sale of Impressionist and 19th-century painting at which more than £2 million was paid for a Monet landscape and just over £1.3 million for Sir John Lavery's The Bridge at Grez.

Here, it was the Lavery price which excited most interest. Bridge at Grez set a new world record not just for the painter but for any work by an Irish artist.

A week earlier, at Sotheby's of London, a Roderic O'Conor still life sold for £276,500, more than twice its estimate and a new world record for the artist. On Wednesday, Walter Osborne's portrait of two little girls made a new Irish record for this artist when it fetched £355,000 at Adam's of Dublin.

Immediately the question was posed: is Irish art on the way up? As so often, the answer is both yes and no.

In a buoyant economy, sales of art will always do well. Many purchasers believe that what they are buying is a good investment and they will be encouraged in this belief by the past week's results. They see art as being not only an attractive commodity but also one with a steadily rising value.

This can be a mistake. The late 1980s were the last time the Irish art market witnessed such a surge of interest but in the recession that followed, many works lost a great deal of their worth. Particularly vulnerable were middle-ranking and prolific artists such as James Humbert Craig, Frank McKelvey and Maurice MacGonigal. Returned too quickly to the auction rooms, they often failed to find new buyers.

Only investors who were willing to hold on to their purchases for at least a decade could hope to recoup what they had initially paid and perhaps even make a profit; in the short term, amateur dealing in art will always be risky.

One explanation for this state of affairs is that although popular at home, Irish art does not necessarily have much of a following overseas. As the current exhibition of Danish art at the National Gallery of Ireland shows, every country in the late 19th-early 20th centuries had its own school of painting similar to that which emerged in Ireland at the time.

All share the same charming, loosely impressionistic style and an interest in landscape and the minutiae of daily life. Irish art obviously holds an appeal for the domestic market but, lacking universality, does not travel particularly well. This inhibits price growth.

It is also a mistake to imagine that because some Irish art is performing well in the auction room, all Irish art will do so. The number of artists whose work has steadily risen in value is actually quite small.

Strong performers include Osborne, Lavery, William Orpen, Paul Henry, William Leech, Percy French, Sean Keating and Nathaniel Hone. Over the past 20 years, most of them have benefited from retrospective exhibitions, monographs and catalogues raison nes, all of which have aided their reputations and prices.

In Northern Ireland, good sums are always paid for locals such as William Conor, Gerard Dillon and Daniel O'Neill.

The most consistently successful Irish artist at auction has always been Jack B. Yeats. Even during his lifetime, he enjoyed the ben efits of a loyal following and since his death in 1957, his work has steadily risen in value. Hardly a year goes by without a new world record being set for the sale of a Yeats picture.

As a result, he has become the yardstick against which the state of Irish art is measured. Always selling well at auction and immediately identifiable, especially in the later years thanks to a bold expressionist style and dashing use of primary colour, Yeats is a favourite among Ireland's new rich; he has become the artistic equivalent here of a trophy wife.

However, his paintings are not typical of either 20th century Irish art or the kind of work usually popular among Irish collectors.

The great majority of artists most prized here - Lavery, Osborne et al - share a romantic sensibility and representational style; their pictures have an immediate appeal and make no great demands on the viewer.

Collectors of Irish art tend to be a conservative bunch, opting to emulate one another's taste rather than take risks.

Another quality the most popular Irish works share is that the artists who produced them are dead. Only a tiny number of living artists command good prices at auction, particularly Louis Le Brocquy and Tony O'Mal ley, neither of whom is at the start of his career.

Young Irish artists must make their way as best they can and ought not to expect very much by way of support from the State's leading collectors. This is why the sale of contemporary British art last Tuesday was so significant; all the pieces on offer - by the likes of Damien Hirst, Rachel Whiteread, Sarah Lucas and the Chapman brothers - were originally bought by one man, Charles Saatchi, who has set the pace for other collectors during the 1990s.

There is no equivalent of Saatchi in Ireland, although wealthy people who could assume that role abound. Without such tangible, high-profile support, contemporary Irish art has none of the excitement, vitality and hype enjoyed by the present generation of British artists. The two states' respective annual art awards provide a convenient study in contrasts.

Whereas the Turner Prize in London is now televised and the subject of intense debate and speculation among the general public, Ireland's Glen Dimplex Award - some how, it is symbolic this should be named not after a great artist but a manufacturer of radiators - barely causes barely a ripple of interest outside the parties directly involved. Young Irish artists, just like so many of their predecessors, must fend for themselves as best they can.

So the response to that question about the state of Irish art is yes, it would appear to be on the way up. Provided, that is, the artist in question has painted tasteful landscapes and is dead.