From: "CWatters" 
Newsgroups: alt.building.construction alt.home.cleaning alt.home.lawn.garden alt.home.repair misc.consumers.house
Subject: Re: Cleaning Mildew from roof shingles ???
Date: Fri, 21 Jan 2005 09:12:43 GMT


"Mark"  wrote in message
news:5duvu0d2953vcfcb3qsm3afo1glcpgi5m4@4ax.com...
> On Wed, 19 Jan 2005 20:23:09 -0800, "John Weiss"
>  wrote:
>
> > wrote...
> >>A strip of zinc at the ridge will do away with most mildew.
> >> The condition you describe is common in the Charleston SC area.
> >> One can see areas free of the discoloration down slope from metal roof
> >> accessories.
> >> Zinc strips for incorporation in shingle roofs are available.
> >
> >Mildew?!?
> >
> >I thought zinc was for moss...  How does mildew grow where there is free
airflow
> >and sunlight?
>
> OK, I'll bite.  How does a zinc strip at the ridge stop mold down on the
> shingles?  Sounds like those magnetic water purifiers you place on the
outside
> of your copper pipes......

They use Copper Sulphate to stop mold on grapes.