[TheForge] What's the science here?

[Chuck Robinson]

Obviously no blade smith's in the crowd.
This is a centuries old Japanese technique. You brush water on the anvil , 
dip your hammer in the slack tub then in one smooth motion you strike your 
billet with the wet hammer as you touch th billet to the anvil face.
The resultant steam blows the scale off the billet instead of pounding it 
into the billet face.
Chuck