Copper and Rain
Name: David A. B.
Date: September 2002
Is there a substance or process which can be applied to copper
flashing and roofing caps to turn them green? in a dry climate of the
western United States, the copper turns dark rather than green.
There are commercial products available to promote the formation of
"patina" on copper. Do a search on www.google.com for "copper patina" and
you will find several sources.
Although I do not know the precise
answer that you are looking for,
I understand your problem.
Copper and bronze are oxidized outdoors
by acidified precipitation. The acidity
of the precipitation that you do get is
not nearly as great as it is in the
eastern United States. Therefore you
don't get the same oxidizing effect.
I can imagine that a very diluted acid,
perhaps Muriatic acid would accomplish the
job. But I would check with a local
commercial builder who uses copper
roofing materials in construction to see
what they say. Any acids, dilute or
not must be handled with the appropriate
personal protective equipment - face shield
or goggles, long rubber gloves, etc.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
Click here to return to the Environmental and Earth Science Archives
Update: June 2012