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RE: moss


Not sure if I was the one or not, but here is some information that I
gathered from a previous posting.

REPLY ONE:  Could you try:

   Pickling Vinegar  9% acidity on a small area???

You can find 20% acidity only commercially--very acidic..but could try.

The only other product I know of, besides Clorox, is Iron Sulfate
heptahydrate (FeSO4.7H20) which is available as a product called Heptasal
from a company in Europe (web site is
www.pvtnet.cz/www/precolor/heptasa2.htm). I would assume any ferric sulfate
product would work (its readily available in the US).
I asked a PhD chemist about the above named product, and received this
reply:  I am not so sure
why the material you describe works for moss removal.  The iron is in what
we call "chemically reduced" form. It will be oxidized to form iron (III)
hydroxide or good old rust.  This oxidation can only take place if
something is reduced.  That must be the moss.  (Bleach and other removal
materials typically oxidize the moss.)  Maybe this is how it is killed.  I
am wondering if rust stains are left behind.  Iron and manganese oxides are
great scavengers for trace metals and should not contribute to pollution in
and of themselves.   You may wish to inquire about the manner in which the
moss is killed or unlatched by this oxidation-reduction chemical reaction.


My thought would be that moss is like fungi and moss has already impregnated
the shingle with its spores and really can't be removed 100% without a chem.
treatment.  We used borate for treating rotting timber piling.

 Salt River Project in Arizona removes their moss from their irrigation 
     canals by using white amur fish.  They have a voracious appetite for 
     moss and algae.  I don't know how they would do in Portland's climate, 
     but that is how SRP handles it.

Margaret and other;

I have a problem with moss growing on our asphalt roof at home.  The moss,
which is very shallow rooted, is very easy to remove with a hoe, flat shovel
or similar type of instrument.  If one wishes, it could perhaps be replanted
to another place.

I don't know the size of the roof or situation to which you refer, but this
is an easy way to remove the moss.  If you're going to re-roof the house, it
shouldn't be a problem.  Besides, I think the growing moss adds a unique,
old world look to the house and  it doesn't seem to create any problems that
affect the integrity of the roof.

Generally moss only grows in shaded and humid environments.  If what
is growing on the roof is moss and not lichens you might try changing the
environment to control the problem rather than relying on chemicals that
only offer a temporary control measure.  If the roof is shaded, consider
trimming the trees that provide shade - this will improve sunlight and air

Margaret Nover
Pollution Prevention Program
City of Portland, Oregon
(503) 823-7623