I've been using a water mist with my aluminum quench plates for a good while - helps cool things nicely. I asked John Foster, a Sandvik technical engineer about this - he felt it was a good idea, but didn't seem to think it was actually needed for the quenching aspect, but certainly didn't hurt anything. I guess I felt when quenching, the idea was to "get it cool" pretty quick? Yea, I know that's not exactly true, I am talking about a "mist", not dunking in a tub of water.
Ken H>