Celebrated British artist David Hockney has unveiled an exhibition to go on show next year which includes his first watercolours.

Although he had previously described watercolour techniques as "wishy-washy" and a medium for amateur painters, he told The Times "you've got to spend time to explore it. I had the time and it's amazing".

Portraits sittings lasted up to seven hours

The portraits include paintings of London film-makers Tom and Charles Guard, and another work John and Robbie: Two Brothers.

Hockney, 64, has not called the paintings watercolours however - the title of the exhibition is Paintings On Paper.

They measure 4ft by 3ft and were made using four pieces of paper, with Hockney painting them in sittings of seven hours, with no initial sketches.

Hockney has never shied away from using new technique

He has had a long tradition of experimenting with new artistic techniques, and recently created artwork by making prints out of colour photocopies and a fax machine, as well as computer-designed art.

The artist got the inspiration for making watercolours after visiting an exhibition of the famed French a watercolour artist Thomas Girtin, who died in 1825 aged only 27.

After trying his hand at watercolours, Hockney was then able to paint a portrait of opera star Sir George Christie and his wife, which had been commissioned by the National Portrait Gallery in 1998.

He travelled to Scandinavia to paint his landscapes

Hockney painted the landscapes during a visit to Norway and Iceland in summer - he said he wanted to paint in a Scandinavian summer because the daylight lasted so long.

"In June the sun never sets at all, You can see the landscape at all hours, 24 hours a day... you get a beautiful light with long shadows," he said.

Hockney claims that cameras are not sophisticated enough to capture the quality of the light - only an artist can do so.

The 42 paintings will go on show at the Annely Juda Fine Art gallery in London from 17 January to 1 March, and at the National Portrait Gallery from 16 January to June.