Sign Language in Prison USA

[in a mo]

There have been many programmes on at the moment regarding American Prisons ,on these there is always mention of a special sign language that the prisioners have devised ,how do they do it ,some of these guys have been locked up in segragated wings of the prison for a very long time but are still able to sign to each other .Any ideas .
Thanks
In A Mo

[Toleman]

i would of thought by sending secret messages. I saw an episode of CSI and im not sure of the science behind this.

They would get a book out of the library which would be noted down - possibly by a prisoner doing a library job.

When they had the book in their cell they would write in urine a message. Then the book would go back. Another prisoner would then get that book out (tipped off by librarian) and tear the page out. If he was to heat up that page with a lighter the acid (?) in the uring discolours to reveal the message.

Maybe this way unless they learned the code before going to prisson if they were in a gang for e.g.

Chris