His output was extraordinary, as many as four or five fully penciled pages a day at times. In a pinch, he could even be faster: When another artist missed the deadline on a full-length Capt. America tale, Kirby drew an entire issue over a weekend.
He saved a lot of time by not planning — he simply would start drawing what he saw in his mind and develop the story as he went along. And he worked incredibly hard, anywhere from 10 to 16 hours seven days a week, with very few days off.