Unseen work by Frank Bowling with hidden image of late son goes on show

The image of the young boy is so faint that it is easy to miss – but if you gaze long enough he gradually materialises through the warm shades of orange, red and ochre.

This is the first view of a previously unexhibited painting by the great abstract expressionist Frank Bowling showing – just about – an image of his son Richard Sheridan Bowling, better known as Dan.

The painting used to hang in Dan Bowling’s London flat but has been in storage since he died in 2001. It is now being brought out to appear in an exhibition of portraits at the Holburne Museum in Bath alongside works from Andy Warhol, Francis Bacon and David Hockney.

Frank Bowling made a series of works depicting maps, often of South America or Africa. Photograph: Holburne Museum

Dan’s younger brother, Ben Bowling, told the Guardian that when he first offered the picture – called Dan With Map – for the exhibition, the curators were not sure it would work because the show was all about portraits and they couldn’t detect one.

Ben said: “A lot of people don’t see this ethereal image of my older brother Dan at first. It’s so faint that you can barely see it unless you know it’s there.”

He suggested it was worth spending some time looking at the picture, which is the first that visitors to the exhibition will encounter, adding: “Our generation complain that people don’t spend long enough in front of artworks. Dan With Map demands that the viewer spends time looking at it and it draws you in. I love the riddlesome-ness of the work.”

The painting was created in 1967 by turning a black and white image of Dan taken when he was four or five into a silk screen, transferring that on to canvas and then partially obscuring it with layers of oil paint.

Dan appears to the left of the picture and one trick to spot him is to look out for the stripes of his T-shirt. Ben said: “He’s got an inquisitive look, he’s very sweet, he’s a very sweet little boy and there he is peeping out from behind these washes of colour.”

The same image appears in about six other works by Bowling. Ben said: “He had three sons by 1967. His sons appear very frequently in his work. The stripes and the T-shirt are a clue to looking for Dan in other paintings.”

Dan became a musician and novelist and died when he was 39. The painting was moved from his flat into storage.

Another riddle in the painting is the map. Bowling, now 90, was keen on incorporating maps into his pictures and Dan With Map includes what seems to be a coastline.

Ben said: “It has a map which we haven’t yet identified at the bottom of the work. I thought perhaps it might have been South Africa. It’s got a sort of an interesting coastline but with his work sometimes what looked like coastlines are simply the movement of the paint over the canvas.”

The Holburne will ask visitors whether they can recognise the coastline.

Bowling is well known in the UK and US but less so in Europe. He has his first solo Paris exhibition in March. “In a way I think of him still as an emerging artist,” Ben said. “It’s great to see this painting exhibited for the very first time – my father’s loving tribute to his first-born son.”

• Iconic: Portraiture from Francis Bacon to Andy Warhol opens on 24 January and runs until 5 May