In the novel Lord of the Flies, Jack changes from a proper, orderly schoolboy to a violent savage. The transformation does not happen immediately when Jack lands on the island, but gradually, as he discovers the joys of the hunt. One chief moment of Jack's descent into savagery occurs when he dons the painted mask for the first time:
"He looked in astonishment, no longer at himself but at an awesome stranger. [...]He began to dance and his laughter became a bloodthirsty snarling" (64).
In this scene, Jack feels the liberation of hiding himself behind paint for the first time. He no longer sees himself as a proper young English boy, for the mask frees him "from shame and self-consciousness" (64). The mask allows him to adopt a new identity; no longer is Jack the hesitant choir boy who could not kill a trapped piglet. Under the paint, he feels fearless and confident.
As if he is addicted to these new feelings of empowerment, Jack takes to wearing the paint at regular intervals, and by the end of the novel when he takes control of the island, he wears the mask all the time. Golding uses the boys' hunting paint as a symbol of their savagery and violence; by the end of the novel when the paint has become like their second-skin, they have truly become savages, on inside and outside.
In what is arguably the largest character transformation in the novel, Jack's change within Lord of the Flies is one that depicts corruption, bloodlust, and transgression of the basic tenants of human "goodness." Jack literally begins the novel as a choir boy--the "chapter chorister and headboy"--a status which seems to imply purity and demand a certain degree of respect from the others.
This persona quickly falls away when it becomes clear that no adults are present to maintain authority and that no one will be coming to rescue the boys. Seeing the opportunity to seize power, Jack attempts to instill fear in the other boys by proclaiming that a beast is prowling the island. He begins to adopt odd and savage habits, painting his face, undermining the leadership of Ralph, and organizing a group of bloodthirsty hunters who wind up in a violent rivalry with Ralph's tribe. The death of Piggy and Jack's indifference to this crime shows that he no longer is just "play acting" at cruelty; he has fully transformed into a sadistic, cruel monster who has no regard for the value of human life or for the longterm survival of the other boys.