The art of mixing and milling requires skillful judgement and deftness of hand. Part of the secret of these tires lies in the careful training and supervision of these skilled workers. Rubber is flopped and turned over and over again, slashed and bunched in some sports, permitted to run thin in others. Although not sticky to the hand, the rubber instantly bonds to itself when loose end are brought together. Firestone (General Tires), Akron, Ohio. Sourced from the Library of Congress.