Why 70% EtOH for cleaning?

[Darci Kane]

mdcabl at cc.newcastle.edu.au wrote:
> I have a very general question.  I was told that 70% EtOH is more effective
> than 95% EtOH for sterlizing and cleaning surfaces.  Tradition of course is to
> use 70% to wipe hoods etc.  I had assumed 70% was used just to cut costs. Can
> anybody out there tell me why 70% is used? Just curious really.

When I asked that question several years ago, I got the answer that
you need the 30% water to lyse the bacteria.  But I admit I don't know
for sure if that is the answer, although it makes sense.