Desperation

When an angel dies, the burnt wings left scorched into the floor, are irremovable.

No matter how hard you scrub.

Both Winchesters discovered this tidbit, in their safe-haven. The Bunker.

Almost every day for two weeks, they scrubbed at burnt wings, desperate to wipe away the visual reminder that he was gone.

Desperate to forget that their last true friend and ally was dead.

Desperate to forget his tortured screams and their utter helplessness.