A perfect profile of the revamped Scottish National Portrait Gallery

• The new Portrait Gallery which will reopen in November. Picture: Phil Wilkinson

TWO years after the Scottish National Portrait Gallery closed its doors for the facelift of a century, the builders have handed the keys back. The gargantuan 18.6 million overhaul promised to strip the 1889 building of decades of architectural clutter and transform its outdated, dimly-lit, and, frankly, shabby feel. As curators begin the six-month task of refilling the building with art, in 17 new galleries, there is every indication it has achieved just that.

About 15 years ago the portrait gallery tottered on the brink of closure, until plans to transfer key artworks for a new Scottish gallery caused wholesale revolt in Edinburgh. Yesterday, director James Holloway could stand on its showcase top floor and declare its new galleries among the best in Scotland, if not the UK.

"What we have got on this floor are fabulous spaces for showing art," he said. The gallery, he suggested, represented "Scotland's family objects. It's Scotland's DNA. It's thrilling that we are going to be back, and firing on all cylinders."

In a tour of the building yesterday, gone were the dimly lit, enclosed galleries with portraits hung in rows on dark fabric wall coverings in decades-old displays. In had come light and air – lots of it, with reopened Victorian skylights, additional walls and low ceilings, mostly added in the 20th century, stripped out, and long views along the building drawing visitors through. It was freshly painted in pale greens and greys, with wood floors sanded back to light natural colours and high iron beams exposed, evocative of the style of St Pancras Station. The project is billed as a return of the building to its late Victorian splendour – albeit with a 48-person glass lift running up through the middle of it.

The goal is to increase average annual visitors by half, from about 200,000 to 300,000. While the gallery has long been a favourite in Edinburgh and Scotland, the focus will be on drawing more outsiders through its doors.

New exhibitions will run from classic Highland Dress portraits, to modern Scots and, critically, to a series of shows on Scottish photography, drawing from the gallery's stellar collection of 38,000 images by the country's pioneers in the art form. "What we have obviously is a work in progress," said the National Galleries of Scotland director general, John Leighton, hailing the building's transformation, on time and on budget. "We have marked a very important milestone."

The gallery will explore issues of history, and issues of identification, and there could be no better time to do it, Mr Holloway said. "This is going to be a gallery about Scotland, about Scottish ideas, about Scotland's place in the world today, a real vital topic of public concern at the moment."

The top floor, now with nine galleries, shows the most dramatic change. The Raeburn Room, where the portrait gallery traditionally hung its most famous classic pictures on walls covered in red fabric brocade, has undergone one of the biggest transformations. The opaque glass formerly used in the skylight has been replaced by clear glass, with hanging fabric "baffles" to keep direct sunlight off the paintings.

The room will now house portraits of David Hume and Jean-Jacques Rousseau by Allan Ramsay, along with other masterpieces in the Citizens of the World gallery, devoted to showing the Scottish contribution to the Enlightenment in "an accessible and distinctive way". It follows the theme of showing old favourites in a new setting, from the Reformation to the contemporary.

The galleries are linked by entrances that invite the visitor to the next space. Low ceilings dating to the 1930s have been removed. Oak and pine floors have been sanded and resealed, while original display cases and even radiators have been saved for re-installing in the rooms. The portrait gallery's signature main hall, with its frieze of famous Scots, has been discreetly transformed, with partition walls blocking windows on one side, and the tiny traditional entrance on the other, both removed, producing a much lighter open feel.

The Scottish National Portrait Gallery was designed by architect Sir Robert Rowand Anderson and opened as the first purpose-built portrait gallery in the world in 1889, in a project largely paid for and inspired by The Scotsman's owner John Ritchie Findlay. The refurbishment of the magnificent Arts and Crafts building has been overseen by Glasgow-based architects Page/Park.

• The new library area. Picture: Phil Wilkinson

The goal, said Mr Leighton, was to clear out a century of clutter, and return an under-used and congested building to its original architecture. It was "refurbished and rejuvenated with 21st century interventions working, extremely tactfully and sympathetically" to enhance the building, he said. They include the new lift, and a new glass mezzanine on the ground floor, with office and children's spaces.

The popular Queen Street Caf has been moved across the building and doubled in size – though the famous cheese scones will still be served by the same caterer.

The building's library, with wooden panelled shelves and an iron balcony running round it, has been moved down a floor, reinstalled, and will be open to the public for the first time. It will include a public area for visitors to relax and read, as well as a private area for researches exploring the photography and print collections.

Exhibitions in main gallery spaces will run for about four years, drawing on the portrait gallery's existing collections with some loans. The small galleries will change 18 months or two years, while the photography gallery will stage three exhibitions every year, exploring "what in many ways is Scotland's greatest art form," said Mr Holloway.

For the first time, the gallery will explore works in different media alongside great paintings, from sculpture to Jacobite glass. One highlight will be the new photography gallery, but photographs will feature throughout. Blazing with Crimson: Tartan Portraits will include six classic portraits of figures in Highland dress. It includes the newly cleaned 18th century picture of Kenneth Sutherland, the 3rd Lord Duffus, resplendent in tartan with his greyhound.

The National Galleries of Scotland unveiled a new brand and identity yesterday, with a logo of a simple uncornered frame. The clumsy name of the "National Gallery Complex" on The Mound has been dropped. The National Gallery of Scotland and the Royal Scottish Academy building will now be known as the Scottish National Gallery.

Over the next six months, with the portrait gallery revamp in sight of the finish line, the galleries are to review their buildings policy. The focus, said Mr Leighton, will be on The Mound, in particular on the National Gallery building, which has not had a facelift for two decades, as well as the way Scottish art is treated in a dreary basement area that often eludes visitors.

After November's public opening on St Andrew's Day, a second opening event may be planned next summer to relaunch the gallery's profile. It appeared clear this week that it will be one of the capital's main attractions.