Necessary items for this method of escape:
Whip (timber + wire + razor) or Nunchucks (timber + timber + wire)
Plated inmate outfit = inmate outfit + metal plate + duct tape
Sail = timber + bed sheet (can only make on prison 6)
Raft base = balsa wood + balsa wood + rope
Makeshift raft = sail + raft base + rope
Putty = toothpaste + talcum powder
Melted plastic = lighter + plastic spoon/fork/knife
Red key mold = red key + putty
Red key copy = red key mold + melted plastic
Recommended, but not necessay item:
Contraband pouch = foil + duct tape
This is the final prison in the game and we can obtain the last 3 achievements here too. As usual start of by boosting all of your stats, then create all the items from the list above, by doing so you should earn Master Craftsman achievement.
Preparing for escape
In this prison our escape plan is mostly beating our way out, yes again(not that it is a bad thing). This time it will not be as easy though.This prison is packed with guards that are stronger than before. You either need whip or nunchuks, these two weapons are the strongest in the game. You also will need a plated outfit and as much medicines as you can get as losing health in this prison will be very common.
The escape
Once you have your weapon, outfit, raft base and key copying materials, start fighting with guards. When you start doing so they will react by rushing on you in groups. Your goal is to send prison into lockdown again and to find the red key. If you have not earned it before, you might earn achievement Disrespect My Authority, which requires knocking out 50 guards. If you want the achievement and have escaped already just reload your save and complete this achievement in this prison.
When you find red key from guards, copy it and do not forget to put it back once you have copied it. When lockdown starts run out through the south door, then head down and right past the electric fence(be careful, do not touch the fence). When you get past the fence run to the right, then when you see a pier use your makeshift raft to the pier. Congratulations, you have escaped the final prison: Hmp Iron Gate and have earned The Escapist achievement!