On February 28, 1935, Gerard Berchet, under the direction of Carothers, produced a half-ounce of polymer from hexamethylenediamine and adipic acid, creating polyamide 6-6, the substance that would come to be known as Nylon. It was difficult to work with because of its high melting point, but Bolton chose this polyamide as the one to develop commercially. He selected Dr George Graves to work with Carothers on the project. Eventually, Graves supplanted Carothers as the leader of the polyamide project. In addition, dozens of chemists and engineers worked on refining polyamide 6-6 into a viable commercial product.