You can keep food and drinks cool on a camping trip or in an emergency without ice or a refrigerator, using the powerful cooling ability of water, which evaporates at 41 degrees, and therefore can cool stuff to 41 degrees, regardless of air temperature, as long as relative humidity is not 100%.
Take a jug of water. Put it in a shallow pan. Cover it with a towel, and let the ends of
the towel lie in the pan. Pour water
over the towel and fill the pan. The
water evaporates from the towel, which wicks more water from the pan, cooling
the towel and the mass of water beneath it eventually to 41 degrees F, the point
below which water stops evaporating. Theoretically, one could cool a box of food by
setting it in a bigger box and covering it with a wet towel that lies in water
in the larger box. I cool and keep
grapes and melon slices fresh, moist and free of flies by covering their bowl
with a wet towel set in a shallow pan of water.
One might think that standing water
would likewise cool off to 41 degrees, because it evaporates. But it has a smooth surface with surface
tension, allowing relatively little evaporation compared to a towel, which has
a rough surface with lots of surface area to evaporate from, and no surface
tension. Towels are made to suck up and
evaporate water efficiently.
Standing or flowing water also sucks
up heat from the mass that it is sitting in or flowing over and holds it in its
mass, so a low-running creek or river or standing water can get warm, because
it does not evaporate faster than it soaks up heat.
The water cycle that makes summer
thunderstorms depends on evaporation and condensation. We used to water most of our in-town
properties and most of our farmland back in the '80s with sprinklers, and we
had frequent wet storms in midsummer, more frequent and stronger uphill and
upstream in Jackson and Klamath Counties,
keeping our creeks running.
In the ‘90s many cities started
raising water prices to save water, regardless of local supply or costs. Drip irrigation and letting lawns dry came
into fashion. Watering plants with drip
saves water at the price of losing the evaporative cooling effect of wet plants
and soil, and thereby reducing the water cycle that makes summer rain. Letting land go dry stops most transpiration
from plants, and makes no rain. Half or more
of our town and farms are dry.
Now we get more dry storms and forest
fires, and creeks going dry that used to run year-round. We have lost nearly a
tenth of an inch of midsummer rainfall per decade for the last two
decades. Our July and August storms used
to be larger than those in June or September.
September issue, published in GardenGrantsPass.blogspot.com,
sold at the Mail Center, 305 NE 6th Street
Gardening
is easy if you do it naturally. Water is not precious; it
overpriced.
Rycke Brown,
Natural Gardener 541-955-9040 rycke@gardener.com
