"The first letter was incredibly difficult," said Sandelson. "I think in the end I just described the garden I was sitting in."
By chance, her correspondent turned out to be Jack Alderman, the longest serving inmate on death row.
And his letters transformed her art.
"It just gradually started to inspire me, comments that he made," said Sandelson. "There was one that he made, a butterfly arrived through the barbed wire and settled on his hand."
She began to paint Jack's world, of isolation and regret, haunting images of his dead wife's clothing.
Alderman was convicted of murdering his wife Barbara in 1974. For 33 years he has claimed his innocence. He has been a model prisoner.
Innocent or guilty, Sandelson believes justice will not be served by executing him.
"Anybody who's spent 33 years on death row has surely done their time," said Sandelson.
Her paintings, as a traveling exhibit and on a Web site, became the core of a campaign to save Alderman's life.
Finally, this summer, Sandelson traveled to the Jackson penitentiary where, behind closed doors, she met her pen pal.
"I'm just so impressed at his courage and integrity, actually, because he knows he probably will be executed," said Sandelson.
Alderman's father was there too, grateful to meet the artists who had painted a portrait of him holding a picture of his condemned son.
"Well I told her that I think angels sent her," said the elder Alderman. "I just think its something, its just unbelievable."
But then, on Oct. 5, a great blow.
Alderman's death warrant by lethal injection was issued.
The Supreme Court will soon consider whether lethal injection is a humane method of execution. In the meantime, some state have halted executions.
Georgia has not.
Alderman is to die on Oct. 19.
The news hit Sandelson hard. Her source of comfort? Alderman himself.
"He is completely ready to die," said Sandelson. "He'd prefer to live, but he's accepted the situation as it is. So he's actually very calm."
And the paintings she hoped might save him remain, a tribute to a most unlikely and enriching friendship.