To add: while I recommend wet soaking to soften dirt, please do understand that if the label gets wet too and stays wet for longer periods, its colour can run, especially when rubbing it with cloth to dry the label. So avoid wetting the label as far as practicable. If it gets wet unintentionally, wipe it dry ASAP. There is very little chance of the label peeling off or the colour running if dried immediately, since the labels are hot stamped during pressing. Do not let it remain wet for long.