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.