Why 70% EtOH for cleaning?

[rand777 at ids.net]

In article <1995Jun1.191457.1 at cc.newcastle.edu.au>, mdcabl at cc.newcastle.edu.au writes:
> Hi all,
> 
> 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.
> Cheers,
> Allen Black
> Univ. of Newcastle
> mdcabl at cc.newcastle.edu.au
> 

70% alcohol will penetrate the cell wall due to the 30% water - Pure alcohol
has a tendency to harden the cell wall and limit the path of the alcohol.