Use your Lifetap spells any time you've taken damage. […] At higher levels, you gain more powerful spells in the Lifetap category.

Witch's mummy, maw and gulf / Of the ravined salt sea shark,

Seed time and Harvest, Heat and hoary Frost Shall hold thir course

This allows the casting of otherwise uncastable materials, with acceptable rejection rates, and can increase ductility by as much as a factor of six.