Why did the boys stare at the copper?

Oliver and the other young boys at the workhouse are always hungry as they never get enough to eat. All they are ever given to is a small bowl of thin, disgusting gruel, ladled out of a large copper vat by the master and his assistants. One bowl of gruel's nowhere near enough, so when the boys have finished eating their meager rations—which doesn't take them very long—they can only sit and stare longingly at the copper, imagining what it would be like to eat more.
No one has the courage to ask for more gruel. That is until the boys hit upon the idea of drawing lots to determine who's going to walk up to the master after supper and ask for more. It's poor old Oliver Twist, of course, who draws the short straw. And so he it is who walks up to the master after supper, with his little wooden bowl in his trembling hands, and makes what, to the workhouse authorities, is such an impertinent request:

Please, sir, I want some more.