Many attempts had been made at developing breech-loading cannons, but the ineffectiveness of the sealing of the breech, creating loss of power and danger for the gunners, had remained a major difficulty. The technique invented by de Bange provided for a doughnut-shaped grease-impregnated asbestos pad to be fitted at the back of the chamber, between a mushroom-shaped head and the screw-breech. When the gun was fired, the expanding gas would push the mushroom head, thereby compressing the pad and effectively sealing the chamber.