From The Collaborative International Dictionary of English v.0.48 :
Unhardened \Unhardened\
See hardened.
From WordNet (r) 3.0 (2006) :
unhardened
adj 1: not brought to a proper consistency or hardness;
"untempered mortar"; "untempered steel" [syn:
untempered, unhardened] [ant: hardened, tempered,
toughened, treated]