Annealed

verb

1. To subject to great heat and then (often slow) cooling, and sometimes reheating and further cooling, for the purpose of rendering less brittle; to temper; to toughen.
2. To cool glass slowly, to minimize internal stress.
3. To burn colors onto a glass or other surface.
4. To make a double-stranded nucleic acid by pairing a single strand with a complementary strand.
5. To strengthen or harden.

   "The experience annealed them, strengthening their resolve."