In another experiment, an attempt was made to fill cannons made of one inch thick cast iron with water only for them too to split when it was frozen. Academics in Florence later tried to fill a ball made of one inch thick brass with water only for that too to crack when it was frozen. They later worked out that the force required to do so clocked in at around 27,720 pounds.

For a more exact answer, you need to once again go back the the water phase diagram, which shows that ice will turn into Ice II when the pressure reaches 300 Mega Pascals, which is exactly, 43,511.31 pounds of force per square inch.

Source: http://www.todayifoundout.com/index.php/...