Just two days after he was due to be released from a prison sentence, Glen Brown was sentenced to a further six years in prison for the attack during a hearing at Sheffield Crown Court on Thursday, November 30.
The court was told how Brown, aged 30, attacked a fellow inmate at HMP Moorland on March 24 this year.
Recorder Christopher Knox told Brown: "Your victim, a man of 23-years-old, who as far as I can see had no reason to expect the unpleasant violence you inflicted upon him.
"You sought him out deliberately. You were armed with a weapon. You slashed him repeatedly across the face with the clear intention of disfiguring him."
Prosecutor Bev Tait said the crude weapon had been made using aluminium.
Less than three months later, Brown was found to be in possession of a second weapon on June 10.
Defending, James Gould, told the court how Brown has a number of personal problems and has been living a 'desperately miserable life' since he was a child.
He said: "He has accepted that whatever was going on at the time, the appropriate way to deal with it was not the way he did."
Brown pleaded guilty to assault and two counts of possession of an improvised weapon at an earlier hearing.
Recorder Knox also sentenced Brown to an extended license period of four years, due to his belief Brown posed a danger to the public.
"You are an extremely dangerous man. You pose a risk to people inside and outside the prison, and for that reason there must be an extended license period."
He added: "You are unacceptable in your current state. You are not fit to be in society. You are a danger to everyone, yourself included."
Detective Constable Michelle Thompson from the Prison Investigation Team said: “This is a significant sentence for a serious and violent attack on a fellow prisoner at HMP Moorland in March this year.
“Brown slashed his victim in the face using an improvised weapon, causing lacerations that required stitches.
“I am pleased he has pleaded guilty to these offences and will remain in prison for the next six years.”