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Hi Judy
exterior paint is a difficult one. It would seem
the biggest environmental impact aside from toxicity of ingredients is simply
the material itself that is consumed in having to constantly renew the finish.
Durability then becomes the crucial issue and performance in the sense that it
is protecting yet another material below it. I think the major local
contamination/toxicity issues are really with the soil and water contamination
from paint degradation and on the larger scale from paint ingredient
manufacture. So long lasting paint goes somewhere in reducing this.
Acrylic water borne based finishes are basically
the standard for exterior paint offering good breathability and durablility with
low voc. The acrylic used is essentially of two types; aryclic and
acrylic/styrene and I don't know anything about the toxicity of either both in
manufacture or use (but would like to). Both perform similarly in terms of
breathability and durability with acrylic slightly better. The main ingredient
that affects long term performance is the filler used. Most are of mineral
origin such as quartz, talc, clay, calcites, dolomite, etc. Quartz, talc,
clay will fade relatively quickly compared to calcite, dolomite but it is
generally difficult to find what a paint is made of as its proprietal
information usually The percentage of filler and pigment is also
important with no more than a 70/30 filler pigment ratio. I looked
for alternative products with a different filler with better durability and
found ceramic based acrylic paints. Unfortunately there is a lot of hype with
these as many manuf. seem to have sprung up with claims about insulative
properties, etc. I did find a good manufacturer of one in Canada
called Envirocoat but the paint is expensive and I don't know how well it
is distributed(amazing paint by the way) and there seems to potentially be a
good US manuf. 'Graham Paint' that manuf. a paint called Aqua-borne Ceramic but
have not used it. Gopd luck getting formulations out of them but perhaps they
may be friendly about it.
so the gist of it is
acrylic (marginally better than acrylic
styrene)
non-chalking fillers (calcite, dolomite, barytes
being the better)
ceramic fillers as the best potential one for long
term durability
proper filler/pigment ratios to acrylic
binder
good luck and let us know what you find
out
John Salmen
TERRAIN E.D.S.
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