A cast with a weight of more than several hundred kilograms was liable to "leak-out" because of the poor quality and strength of the moulds. This would deform the surface of the cast or even make the cast a complete failure. Since the Yongle Bell was 46 tons in weight, the casting produced great force of impact and pressure on the moulds. The method of pit shaping and pottery molding provided a good solution to the difficult problem. When the moulds were combined, the space between the outer mould and the wall of the pit was filled with rammed earth so as to increase the strength of the entire mould. The successful casting of the Yongle Bell made an outstanding contribution to the casting industry and scientific and technological circles in China and the world as a whole.
