A weapon has an initial hardness of 0/2. By adding hardness, the hardness can be increased to 1/2 or 2/2.
If refinement fails, then the weapon does not break, but hardness and maximum hardness decrease by 1.
For example, if a weapon with 1/2 hardness fails refinement, then the hardness will be reduced to 0/1, and the weapon does not break.
The maximum hardness can be increased by 2 once.