Prison art

In the late 1940's, as the Communist regime was tightening its grip on Bulgaria, my father was among those who opposed it. He became member of a secret anti-communist organization. Unfortunately, the founder and leader of the group was a provocator. He lured the others and then gave them up to the authorities, quite as O'Brien did with Winston Smith in Orwell's 1984. They served prison time, 4 years for my father. While awaiting the trial, they were placed in the Sofia Central Prison.
Several days ago, my father remembered the prison church. Until 1950, priests in magnificent Orthodox vestments were allowed to read sermons there. The church was beautifully decorated. Inmates serving sentences in the first half of the 20th century had painted murals on the walls. They were excellent, although the prisoners were amateur artists. My father remembers, in particular, a Christ walking on water painted by Anton Prudkin. This interesting person was naturally drawn to the sea theme because he was a sailor. He was a terrorist and Russian agent and this was why he was jailed from 1925 to 1936 and later executed in 1942. However, he was not entirely evil. In 1939, he was captain of a ship that sailed 3 times between Bulgaria and Palestine, bringing there more than 2000 Jewish refugees.
In 1950, the religious freedom in the Sofia Central Prison was put to an end. The church walls were whitewashed with lime. (The Bulgarian reader will remember the moment in Ivaylo Petrov's novel Wolfhunt where the Communists led by Stoyan Kralev burn the icons of the village church.)
What is remarkable, the prison authorities themselves were clearly reluctant to destroy the murals. The chief jailer in front of some inmates scratched the newly formed lime layer with his fingernail and said, "Oh there is no problem. It will be easily scraped away." (The Communist regime often abolished the acts of folly it had ordered itself, sometimes quite shortly after imposing them.)
However, in this case the order was not cancelled. My father was transfered to another prison and had no more first-hand information, but other former inmates later told him that the lime layer had become tight and impossible to remove. My father wasn't surprised because he knew that lime becomes more and more stable with time. As he explained to me, this happens because calcium oxide takes up carbon dioxide from the air and turns into calcium carbonate.
At one moment, the former church reportedly became room for executions.
What has been its fate in recent years? I have no idea but I think that experts in chemistry and restoration must know a way to remove even an old, tight lime cover without much damage to the underlying paintings. But more than half a century later, does the prison personnel include even one employee who knows about the murals? And would anybody care?
There is little time to restore the prison art and capture the images. The municipal authorities of Sofia have scheduled the Central Prison building for demolition.