The sale last month for a record price of a painting by John Luke has increased interest both in this artist and in his technique of tempera. To deal with the latter first, tempera was much used during the Renaissance period but fell from favour once oil painting became popular. The technique is difficult to master because it involves pigment added to a natural emulsion of egg yolk thinned with water. This is applied to a panel prepared with several layers of gesso, an absorbent base. Tempera paint dries quickly, becoming resistant to water after just a matter of minutes.

This allows the artist to build up layers of luminous colour by painting over the existing work. In Luke's case, the luminosity was enhanced by an overlay of oil glazes.

Other than an interest in the convoluted, and an exceptionally orderly character, there seems to be no reason why John Luke should have adopted tempera as his favourite medium, since he only learnt the technique at the age of 30.

Born in Belfast in 1906, he studied with Professor Henry Tooks at London's Slade School of Fine Art; even then, he was renowned for his meticulousness. Having returned to Ulster, he was already exhibiting examples of his art in the early 1930s, even before he began to work in tempera. During this early period, he also produced a number of sculptures as well as murals; he continued to receive occasional commissions for both throughout his life.

However, the distinctive Luke style, with its emphasis on landscape and the human figure shown in brilliant colour and a strongly rhythmic sense of line, soon began to emerge. It was in 1936, the year he painted The Bridge (sold for a record price of £441,500 last month at Christie's), that he started to work with tempera, which was evidently suited to his character and artistic intentions. According to his friend John Hewitt, writing in The Studio in 1949, Luke began by sketching in the open air, later modifying what he had produced to create a more abstract and sinuous design. Hewitt also noted that although the finished work can often look almost simplistic in its ease and grace, it was in fact the result of considerable hard work.

"This, and the care with which the materials for picture-making are prepared and handled, inevitably make his work a slow process, so that Luke seldom produced more than two pictures each year, although employing himself regularly at his craft for long periods." The relatively small number of works he completed helps to explain why prices for Luke can be so much higher than those of his more prolific contemporaries. Luke's The Bridge - which had also made a new record for the artist at auction when sold by Christie's in Belfast almost 11 years ago for £176,000 - perfectly represents his mature style, although unlike later works, it shows an identifiable location. This is the five-span Shaw's Bridge over the River Lagan a few miles from Belfast.

The same view was shown by Luke three years later in another tempera work, which was also included in the recent Christie's Irish sale. Darker in tone and more realistic in style, it failed to secure a buyer. This was one of six John Luke pictures offered for sale in the same auction, although none of the others was so representative of the artist at his best as The Bridge.

John Luke's seminal work, The Bridge, which fetched a record price of £441,500 last month at Christie's