From: mike wilson
From: "P. J. Alling"
They look like they could be oak leaves, which are full of
tannins. That would stain the concrete and eventually be
weathered away.
What I find odd is that they are (presumably) quite water soluble, to
be leached out of the leaf into the concrete by rain or dew but then
they are not washed away from there. Very, very intriquing. The
other possibility is that it is a wax covering that is somehow being
transferred to the concrete and then resisting removal. Plant waxes
are rather persistent chemicals - carnauba wax, found in many
polishes until the advent of modern polymers, is/was extracted from
the surface of leaves.
Look like red maple leaves to me, but there are several different leaves
that will leave stains like this.
The surface of concrete, even smooth finished cement, is rather porous.
When a leaf lays there and gets wet the stain seeps into the surface.
This is especially true if the leaf is covered with something like snow
and kept in contact with the surface for a while.
But it's a seasonal thing that comes and goes. Keep an eye on that
stain, and next spring/summer, UV light will bleach it back out and the
cycle will start all over again next fall.
--
PDML Pentax-Discuss Mail List
[email protected]
http://pdml.net/mailman/listinfo/pdml_pdml.net
to UNSUBSCRIBE from the PDML, please visit the link directly above and follow
the directions.
