Conversion. Beverage containers to aviation oxygen cylinders. Once the two-half cylinders are joined together into a complete shatterproof high altitude flying oxygen cylinder on the production line of a huge rubber factory now producing metal essential for the Army, all traces of inside weld scale must be removed to prevent contamination of oxygen. In this process, a special chemical solution is drawn through the cylinder at controlled temperature and all foreign matter is removed. Firestone, Akron, Ohio. Sourced from the Library of Congress.