THIS is the tale of Write Or Wrong. On the one hand, those with an urge to express themselves in graffiti have been asked all summer to resist defacing the 49 repro paintings that make up the Grand Tour of York art trail.

On the other, York Art Gallery’s writer in residence, Tracy Chevalier, is urging visitors to write on the blackboards that run around the walls of her new exhibition, A Thousand Words.

White chalk is provided, and so too are postcards, pencils, even a rubber and a sharpener (for messages to be despatched to the soldiers depicted in Richard Jack’s Victoria Station: Return To The Front, an epic First World War painting newly restored and returned to the gallery walls at Tracy’s prompting).

If, as the saying goes, a picture paints a thousand words, then the American author has taken that further in her literature, most famously in Girl With A Pearl Earring, her story inspired by the Johannes Vermeer portrait.

“I’ve gone back to that painting again and again,” says Tracy. “I’ve written about it, I’ve talked about it and I still find new things in it, like the light.”

There is no need to write a thousand words, but if you feel inspired by Tracy’s exhibition introduction, written in chalk on the wall by the gallery door, then write away.

The idea behind the 45-year-old Washington author’s first exhibition as a curator is to reflect on how a piece of art captures a central moment in a story. Tracy releases that frozen image in her books, and now she is encouraging you to join her in exploring storytelling in art.

“When I look at art I often think about the stories that might emerge,” she chalks up on the wall. “If a painting offers us the middle of a story, what happened before? What happened after?”

Working her way through the complete catalogue of the York Art Gallery collection, Tracy has selected 17 paintings – mostly featuring people, but also some landscapes and an abstract work by John Piper – plus two ceramic pieces. She has restricted the number in order to leave plenty of space between the works, as if to allow them to breathe with life.

“I’ve chosen the works of art here because I think they’re full of possible stories,” her chalkboard continues. “We’ve given you the space and materials to make up beginnings, middles and ends for them. I’ve written a few words myself – it’s hard to resist.

“Once the walls fill up, we’ll photography your words, then erase them and start again.”

Tracy’s words strike a confident tone, and on the evidence of a visit on Tuesday afternoon, such confidence is well placed as the walls were thick with words, in English and foreign languages too, although none of them matched the wit, mystery and tantalising story possibilities of Chevalier’s thoughts, written neatly in blue ink on notes beside various paintings.

“Vodka. No one can smell it, especially once I have a mask on,” reads her note of foreboding that accompanies Dame Barbara Hepworth’s sinister, cold, blue study of a doctor, Surgeon Waiting.

“I think this is the one that people will write loads about, just because it’s so evocative,” says Tracy.

“But I have no idea how people are going to respond. Are they going to feel intimidated or think it’s stupid, or are they going to love it and fill it up with writing? That’s always what happens when something is not set in place and you have to hand over control,” Tracy says.

Living in London, she has been travelling to York for two days a week during her residency, and last Friday she was leaving town again until October.

“It’s a weird feeling. I just have to let go and hope it all goes OK, but I’m sure I’ll be ringing in, saying, ‘How does it look? Has anyone written anything interesting?’,” says Tracy.

She recalls her original brief for the show.

“I was told I could do anything I wanted, so long as I used the gallery’s permanent collection,” Tracy says.

“Originally I was told I could use the small room upstairs, and I thought, ‘Great, how much damage can you do in a small space?’ “Then this big space became available and at first it was daunting because there’s nothing that cuts the room up. It’s just a big room with a gorgeous floor and lovely lighting.”

Picking paintings from a catalogue where they all appeared in the same size, she had no initial idea of the scale of the works she had earmarked. As chance would have it, they have come together well to meet Tracy’s aim.

“I knew I wanted to shake up people’s expectations of going to an exhibition, where you know it’s usually going to be quiet and you look at one painting and then another, and maybe you will learn something about an artist and then you leave,” she says.

“I’ll go into a room, see 20 paintings, maybe like only one of them and end up making a story about that one painting. You look at it, you think, ‘What’s the beginning – what’s the ending?’ and when you do that you can spend ages in front of it. So that’s why I decided to give everyone the chance to express themselves in front of a piece of art.”

A video of children talking about the four portraits on the back wall spurs further thoughts, and so does a case full of wartime memorabilia.

“The idea is to bring down the barrier with this exhibition, so that you never feel that the art is more important than you are. It should never be like that. The people of York own these paintings and should feel proprietorial about them,” says Tracy.

“I hate it that I feel guilty if I don’t respond to a piece of art and think there’s something wrong with me, whereas with a book or music, you can say, ‘Actually I don’t like that and I’ll look elsewhere’. But I’m quite happy for people to walk around this exhibition and say, ‘I don’t like any of this’. That’s a perfectly legitimate response.”

Not everyone shares Tracy’s enthusiasm for freeing paintings from their moment into the world of words. Witness a couple of the postcards tucked away among the more romantic thoughts on the message board by the Richard Jack painting.

“The art speaks for itself – if they required words, they’d have been poets instead,” reads one.

“The art chosen for the exhibition is excellent, but without her one thousand words. Leave that to the artists,” reads another anonymous missive.

Tracy no doubt would beg to differ. Perhaps she would prefer to dwell on the cryptic comment on the last corner space on the blackboard strip beneath Return To The Front.

“No book can ever tell my story,” it said, maybe offering a challenge to the author.

* Tracy Chevalier is now busy finishing her latest novel, Spare Bones, for editing in January and publication in Autumn 2009. “It’s nothing to do with art,” she says. “It’s about fossils: the story of Mary Anning, a fossil hunter in Lyme Regis in the early 19th century.”

* A Thousand Words, curated by Tracy Chevalier, runs at York Art Gallery until January 4 2009.