Mahogany today is so closely associated with excellent quality antique furniture that it always comes as a shock to realise the wood was not available in this country before the second quarter of the 18th century. Prior to that date, other materials had been used, their existence primarily known through inventories such as that of the Earl of Cork in 1645 and the Earl of Fingall in 1736; little furniture produced before 1700 has survived. Favourite woods during the earlier period tended to be oak, of which Ireland had a plentiful supply, and walnut. Most of it was destroyed during the successive upheavals of the 17th century and even from the first decades of the 18th century only a small number of items remain, most notably a series of very fine marquetry-inlaid walnut writing desks one of which - now in London's Victoria & Albert Museum - is said to have belonged to Dean Swift.

The Fingall inventory mentions japanned furniture as well as items in oak and walnut. A mere decade later, an inventory produced for William Smyth of Co Westmeath includes many mahogany furnishings, so rapid was the emergence of this hard wood as a favourite among Irish craftsmen and their clients.

One reason for mahogany's appeal lay in its excellent response to carving and subsequent polishing. Elaborately carved surfaces are a particular feature of 18th century Irish furniture. It has also been suggested that the Irish fondness for dark woods stemmed from the traditional use here of bog oak, the colour of which is almost black.

Mahogany first came to Ireland around 1725 in ships from the West Indies. Initially it was simply used as a ballast aboard these vessels. There was considerable demand for furnishings of all kinds during the early 18th century as the country recovered from a succession of wars that had left it exhausted. During the course of the century, Dublin and other urban centres expanded rapidly, and so too did the number of large, private houses on Irish estates. All of these properties had to be furnished and by 1786, it has been estimated, there were 28 cabinet makers, 12 carvers and gilders, three joiners and upholsterers and six harpsichord and music instrument makers registered in the capital alone. Their clientele would have been essentially the country's nouveau riche, many of them relatively recent arrivals in Ireland where they had been granted land as a reward for loyalty to the English crown. Some of our greatest 18th century houses were built by self-made men and the robust vigour of Irish mahogany furniture at the time reflects their own temperaments.

Compared to what was being produced elsewhere, Irish early 18th century items can sometimes seem coarse and lacking in subtlety; they were designed to reflect their arriviste owners' prestige and wealth and therefore needed to make an immediate impact. This also explains the popularity during the same period for lavish stucco work - just like early 18th century furniture, it made an instant impact on viewers.

To the modern eye, houses then would have been relatively sparsely furnished and therefore it was even more important that any item on display was noteworthy. Here is another reason why so much Irish furniture is profusely carved. But it is possible that a national love of ornament for its own sake may also have been in part responsible for carved mahogany's popularity.

In an examination of early 18th century Irish marquetry decoration (The Irish Arts Review, Volume 13), the Knight of Glin features a writing table and cabinet the lower section of which is carved with fantastical twin-headed and curly-tailed canines, the direct descendants, it might be thought, of mythical beasts seen in the Book of Kells and similar Celtic manuscripts. Certain stylistic elements occur repeatedly in 18th century mahogany furniture, suggesting Irish craftsmen were using the same few pattern books and sources of inspiration. Exuberance of decoration means that the overall flavour of the work is baroque, long after this style had fallen out of fashion elsewhere in Europe.

Among the most frequently featured details are lion head masks, baskets of flowers or scallop shells in raised relief on the centre of sidetables, and legs terminating in hairy paws - all four legs of a chair may be so decorated rather than just the two in front. Relief details are often seen against a background of finely-carved diamond trellis and the shell motif turns up also on chairs and sofas.

Wherever an opportunity for carving presents itself, this may be exploited. So, for example, the bulbous hocks on the corners of tables, desks, chairs and stools may be ornamented with carving, frequently using an acanthus scrollwork pattern. Cabinets and mirrors tend to have a swan-neck pediment, sometimes framing an urn or cartouche; these pieces would usually have at least some gilding and marquetry work was also much favoured. A number of problems arise when considering Irish furniture of the first half of the 18th century, not least that of attribution. Considering both its quality and enduring popularity, surprisingly little research has been carried out in this field and a definitive guide remains to be written.

For the moment, attribution remains difficult because Irish craftsmen did not sign their work except in rare cases, the best known of which would be the Dublin firm of Francis and John Booker who produced highly distinctive gilded and pedimented mirrors. Adding to these difficulties is the fact that much Irish furniture was exported to the United States earlier this century when the contents of so many country houses were dispersed at auction.

There are definite similarities between 18th century Irish and American furniture - hardly surprising since many craftsmen from this country travelled across the Atlantic at the time - and today it would be almost impossible to pick out which pieces were created for clients here. What has gone from these shores is unlikely ever to be reclaimed. Heavily-carved mahogany furniture remained in production in Ireland long after it had started to fall out of favour elsewhere. However, by the 1770s, a change in direction was definitely perceptible and Adamesque neo-classicism quickly became the dominant style.

As a result, from this period on it becomes increasingly difficult to tell Irish from English furniture. The age of exuberance lasted less than 50 years - another reason why the amount of furniture available is restricted.

One of the best places in which to see such work is Malahide Castle, where a large selection of Irish furniture is on permanent display.

However, from next Wednesday until Saturday, 29th August, Johnston Antiques is presenting an exhibition of Irish Georgian furniture at Dublin's Newman House.

The majority of 21 items on show date between 1730 and 1760 and include a Booker mirror, a mahogany cabinet formerly in Adare Manor, a mahogany kneehole writing cabinet and several console and side tables. All pieces display the decoration typical of Irish furniture.

Admission to the exhibition costs £10 including a copy of the colour catalogue with funds raised going to the Irish Georgian Society. For further information, contact Johnston Antiques, Tel. 01-4732384.