Every filmmaker deals with obstacles. Extras, even though their roles are minor, are still needed to make prison look like a prison and not a ghost town with barred windows. The inmates were supposed to be portrayed by the local inhabitants, but they left after one day of shooting to go back to their regular nine to fives. So, the director had to find a quick solution.
To get the extras they needed, the production team went to a halfway house. Many of the inmates in the movie were real ex-cons. So it’s safe to say that they were ready for their roles.
Not Exactly a Real Jail
Shawshank Prison isn't a real prison at all. The only real shots were the exterior ones done outside the abandoned Ohio State Reformatory in Mansfield. The inside of the reformatory was such a disaster that the filmmakers shot the interior shots on a sound stage.
They figured it would be cheaper to create a replica than try to renovate the decaying jail. They definitely fooled us (and the Academy). The set design was so convincing that everyone thought it was filmed in a real prison.
Shawshank References
Stephen King loves Maine. He loves it so much that he lives there, and also sets many of his diabolically frightening novels in the Pine Tree State. 'The Shawshank Redemption' is no exception. What King also loves to do is interconnect his books. Shawshank is mentioned in many of his works.
In the film 'Dolores Claiborne', based on one of King's novels, Dolores yells at her husband that he will do time in Shawshank for what he did to their daughter. Shawshank Prison is also mentioned in 'The Fifth Quarter', 'Needful Things', 'Sun Dog', and more.
A Real Portrayal
Clancy Brown, the actor who plays Captain Hadley, was approached by real correctional officers to help him make his portrayal as realistic as possible. Brown didn’t want to distort the image of real correctional officers, so he turned them all down.
Brown knew that to portray Captain Hadley, he had to go all-in on the evil aspects of the character. He did such a great job that Captain Hadley is still one of the most hated movie characters of all time.
Fake Sewage
During the climax of the movie, Andy escapes prison after digging a hole in his cell wall and crawling through the sewers. As you can imagine, he gets elbow deep in his fellow inmates' waste, among other things. Don't worry, the excrement wasn't real. The director didn't make Tim Robbins crawl through actual human waste.
The sludge was much tastier than you think, because the fake waste was a mixture of Chocolate syrup, sawdust, and water. According to the people who still visit the old sets in Ohio, the pipes still smell like chocolate to this day.