After 126 years, a lost sketchbook by Vincent van Gogh was revealed to much fanfare worldwide Tuesday — thanks to a Canadian art expert — but not everyone is convinced of its authenticity.

Canadian art historian Bogomila Welsh-Ovcharov's Vincent van Gogh: The Lost Arles Sketchbook contains many drawings from the most significant period of van Gogh's life, when he was living in the south of France, working on some of his most famous paintings but suffering from the psychological torment that led him to cut off his ear and spend months in hospital while continuing to create.

Welsh-Ovcharov, a retired University of Toronto professor who has curated many exhibitions of van Gogh's work and is considered an international authority on the artist, was visiting France in 2013 when she was asked by local art scholar, Franck Baille, to look at an album that could contain some of the artist's material.

Retired University of Toronto art history professor Bogomila Welsh-Ovcharov is one of the world's top experts on the work of Dutch painter Vincent van Gogh. (CBC)

As one of the world's top authorities on van Gogh, she'd been asked many times to check artwork found in an attic or a garage, only to discover it was a print or a poster. Her expectations were low. But this time, she said, she got the shock of her life.

"When I opened it up, the first thing I said was, 'No, unbelievable!'" Welsh-Ovcharov told CBC News in an exclusive advance TV interview at her Toronto home.

"The first drawing that I took out and held in my hands, it was a moment of total mystical experience: 'Oh my goodness, this is impossible!'"

What's more, as she leafed through the sketchbook, she soon realized it contained an astounding number of drawings: 65 in all.

Welsh-Ovcharov shows CBC reporter Deana Sumanac-Johnson some of the lost van Gogh sketches that she authenticated. The 65 drawings are published in her new book, Vincent van Gogh: The Lost Arles Sketchbook. (Nigel Hunt/CBC)

Her initial caution about the works' authenticity quickly gave way to enthusiasm as she examined their quality and technique.

"The patina is there, the brushwork with the reed pen, the way he executes with such vibrato, with such passion, with such force every individual object in nature — you can't duplicate that," she said.

"I never expected to find something like that. It is a culmination to every art historian's life, career."

However, as Welsh-Ovcharov launched Vincent van Gogh: The Lost Arles Sketchbook at a press conference in Paris Tuesday morning, the Van Gogh Museum in Amsterdam released a statement disputing the authenticity of the sketches.

The museum states its experts have been aware of the album for some time (as early as 2008) and, based on "high-quality photographs sent to them of 56 of the 65 drawings," concluded they are imitations of van Gogh sketches. The statement, which outlined the museum's reasoning, called the drawings "monotonous, clumsy and spiritless."

Welsh-Ovcharov's editor, Bernard Comment, said a point-by-point response to the museum's statement would be published later this week.

"We have not changed our minds and are very happy that from now on everybody can make their own opinion after seeing the drawings and reading the analysis in the book," he said.

Welsh-Ovcharov was also passionate herself when answering questions about the dissenting opinion in Paris.

"When I was a university professor and I taught courses on connoisseurship and on art history, that was the worst thing anyone can do: to tell me that they made a decision on what is a work of art by a photograph," she declared.

"When I know something is a van Gogh, I know it is a van Gogh," she said.

"And when a museum tells me that they have the priority and have, in some ways, a conflicted interest, a vested interest — I think we're opening up a real can of worms of where the authority lies in connoisseurship."

Business ledger became sketchbook

As Welsh-Ovcharov began the painstaking process of authenticating the works over the past three years, the story of the sketchbook also came to light.

It was, in fact, an old-fashioned business ledger, approximately 26 by 40 centimetres, that had been given to van Gogh in May 1888 by the owners of a café in Arles, where he was temporarily living. The high-quality blank pages were ideal for use as an artist's sketchbook.

Two years later, after van Gogh cut off his ear following an argument with the painter Paul Gauguin and spent many months in hospitals in Arles and Saint-Rémy, a doctor he had befriended returned the book of drawings to the café owners. Then for generations, it languished, likely stored with other business ledgers.

Fortunately, there was independent proof that this was van Gogh's work, thanks to a small notebook that had also belonged to the café, documenting daily activities. It contained an entry for May 20, 1890 noting that van Gogh's friend, Dr. Felix Rey, had returned a large album of drawings, along with some empty olive jars and towels, to the café owners on behalf of the artist.

Two months later, van Gogh fatally shot himself.

The works contained within the book's pages are being called 'the most revolutionary discovery in the entire history of van Gogh’s oeuvre.' That's according to van Gogh scholar Ronald Pickvance, who wrote the book's foreword. (Abrams Books)

The sketchbook is significant for many reasons, according to Welsh-Ovcharov. It's the only known sketchbook from his time in Provence, where he was "in one of the most productive, optimistic phases of his life."

"Those years have been considered some of his most important years because the art that he produced is iconic in every sense, revolutionary for artists to come in modern art," she said.

It was there that he created many of his best-known paintings, and the drawings show how the artist was sketching to prepare for his paintings.

Since few other sketchbooks exist — none from that period — it was previously believed van Gogh made his drawings after his paintings, to send to his brother or potential art collectors.

In the published version of the sketchbook, Welsh-Ovcharov also provides a detailed analysis of the paintings that were based on these drawings.

She hopes that not just art historians, but also the many people who love and appreciate van Gogh's works, will gain deeper insight into the mind of the artist by learning more about his creative process.

Art historian Bogomila Welsh-Ovcharov explains to CBC's Deana Sumanac-Johnson how Vincent van Gogh sketched in preparation to paint The Olive Trees, considered one of his masterpieces. 2:08

Other experts agree.

"It's hugely important because there's so much interest in van Gogh. And the sketches help to explain, of course, the genesis of his paintings and his ideas," said Katharine Lochnan, senior curator of international exhibitions at the Art Gallery of Ontario.

Welsh-Ovcharov worked with Lochnan as a guest curator for the current AGO exhibition, Mystical Landscapes: Masterpieces from Monet, van Gogh and more.

Van Gogh's The Olive Trees (1889) is one of the paintings based on a drawing in the newly found sketchbook. The work, on loan from New York's Museum of Modern Art, is currently on display at the Art Gallery of Ontario. (The Museum of Modern Art )

Lochnan, who admittedly hasn't yet read the new book, calls the apparent discovery and publication of these drawings "an extraordinary event."

"It's wonderful in art history when works of art suddenly turn up that we had no idea existed and help us put together more pieces of the jigsaw puzzle of an artist who is probably the most beloved artist in the world today."