On 11/06/2014 10:10, Ian Bingham wrote:
and"Desperate Dan" wrote in message
...

If the wooden screen wasn't maintained properly, painted regularly, then
the wood would absorb water, thus cooling the screen by evaporation.
Obviously, this doesn't happen with the plastic version. I have noticed
that the shiny white on the plastic does grow dull (almost matt) with
age. I'm sure any trials have been conducted with nice new screens so
what happens over time has probably never been looked at.

==============================

OTOH with a poorly maintained screen, the paint would dull and peel and
algae grow on it, reducing its reflective properties, and so it might
tend to OVERread! Like so many things in Meteorology, infinitely
complicated.

Ian.

There was a conjecture that when they switched from what was just an
inorganic lime whitewash to TiO2 acrylic resin based paints.

Whilst I don't consider Wattsupwiththat a sound reference site he has at
least done some experiments on the topic (assume cherry picked data):

http://wattsupwiththat.com/2008/01/1...en-paint-test/

I am genuinely curious as to why whitewash surface appears to come down
faster from the local maximum temperature. The bare wood version isn't
all that different from the painted one and the acrylic paint tracks the
night minimum slightly better (if his data are to be believed).

--
Regards,
Martin Brown