The face painting Jack does to prepare for the hunt is at first an attempt to solve a problem. He thinks that the pigs can pick out his face while he is stalking them, so decides to smear some clay and charcoal on his face as a form of camouflage....
The face painting Jack does to prepare for the hunt is at first an attempt to solve a problem. He thinks that the pigs can pick out his face while he is stalking them, so decides to smear some clay and charcoal on his face as a form of camouflage. However, his mask becomes much more than a hunting aid. It becomes, in essence, a new persona for Jack.
Jack's first attempt at face painting is not successful. When he looks at his reflection in the water, he is displeased. It's significant that on the second try, he "plans" his face, drawing a specific design:
He made one cheek and one eye-socket white, then he rubbed red over the other half of his face and slashed a black bar of charcoal across from right ear to left jaw.
This was better:
He looked in astonishment, no longer at himself but at an awesome stranger. He spilt the water and leapt to his feet, laughing excitedly.
The mask has transformed Jack from the sandy-haired, freckled boy into a fearsome killer. More than that, all the limitations and emotions that Jack feels are forgotten with this new persona. For instance, the mask helps Jack assert dominance over the other hunters, and in a sense it frees him from the need to tend the signal fire.
In that sense, the mask can be seen as a departure from rationality. Jack's bloodthirstiness is enabled by the mask; his new personality is in stark contrast with Ralph's rationality. Ralph wants a ship to see their signal and rescue them; Jack, in his mask, simply wants to kill, both for the fun of it and the personal glory that it can bring. For him, this is an imperative that supersedes all other considerations.