User blog comment:Xilinoc/Ch. 542 - THE BLADE IS ME/@comment-4207271-20130620040906/@comment-3250274-20130620162334

I do believe the heat that is being referred to is the heat given off from the actual forging of the Zanpakuto, just like a normal forged sword needs to be cooled fast in water, so does the zan. Ichigo's immense reiatsu created immense heat, thus the evaporation of the water. IF you look the water is moving away from them, not towards. It was not absorbed.