WATER SOLUBLE SOILS
Water soluble soils are such substances as
sugar, starch, gums, salt, flavoring agents, and
syrups, as well as a wide variety of substances
generally found in such foods and beverages as
mustard, catsup, soups, and soft drinks. Per-
spiration stains are also included in this category.
These types of soils are removed during the
normal laundering process.
Insoluble soils, substances that are not soluble
or dissolvable in either water or chemical solvents,
are the materials most commonly found in fabrics
and constitute the bulk of the soils removed in
the laundry. Included are earth, concrete dust,
sand, carbon, ashes, lint, hair, cosmetics, and
dandruff. These types of soils are usually less
visible than oils, greases, or food stains, but they
contribute greatly to fabric damage due to fiber
Most insoluble soils are readily dispersed
during the wash cycle, but their complete removal
may prove more difficult. Such soils are some-
times redeposited on the garments during the
laundry process, a condition that can cause
graying of the fabric.
Special soils are insoluble in either water or
laundry chemicals. They may be removed partially
or entirely using spotting operations. These soils
include nail polish, paint, ink, various kinds of
adhesives, and so forth. Spotting operations are
discussed in the dry-cleaning chapter.
THE WASH WATER
Water is the most important item used in a
laundry. Not only is it needed in quantity, but the
quality of water used has an important effect on
the washing process.
At sea, where quantities of suitable wash water
are always subject to greater limitations than
ashore, you may not always have enough soft
water available. To conserve fresh water, you may
be required to use seawater.
When water comes from clouds as rain or
snow, it picks up carbon dioxide gas. As the water
seeps through the ground, the carbon dioxide gas
dissolves limestone and some other substances,
and the water collects calcium and magnesium
salts. The salts are in the form of bicarbonates,
chlorides, nitrates, and sulfates. The kind and
quantity of these substances are determined by the
soil the water passes through. Water that contains
an appreciable quantity of salts is HARD water.
SOFT water is water that has not picked up salts
from the earth, or water that has had these
substances removed or neutralized. Since seawater
contains the concentration of salts, it is the hardest
of all wash waters.
TYPES OF HARD WATER
In laundry terminology, hardness in water is
the power to kill soap. When soap is added to
hard water, the calcium and magnesium salts in
the water combine with the soap to form insoluble
lime soaps. These soaps then unite (precipitate)
in the form of a sticky, insoluble deposit. This
reaction kills the soap and makes it useless for
washing, and the sticky deposit traps dirt and puts
it back on the fabric in the form of scum. If no
dirt is present, the scum is white and is seen as
a film on the clothes.
There are two types of water hardness:
1. Temporary hardnessWater that contains
calcium and magnesium bicarbonates is called
temporary hard because these elements can be
removed by boiling. Scale on the inside of steam
kettles and steam boilers is due to the precipitation
of insoluble carbonates as the hard water is boiled.
2. Permanent hardnessWater that contains
calcium and magnesium chlorides that are NOT
affected by boiling is said to be permanently hard.
Permanent hardness requires special treatment
with chemicals or by distillation.
WATER SOFTENING METHODS
The methods generally used to soften water
are known as the base exchange and distillation.
The base exchange method softens water when the
compounds of calcium and magnesium in the
water are exchanged for compounds of sodium
which do not cause hardness.
The distillation method softens the water when
it is boiled and the vapor is cooled by running it
through pipes immersed in a cold solution to
reconvert it to water. The distillation method is
used to make seawater usable for a ships boilers
and other shipboard uses. Seawater distillate is
not pure water, but it contains only about
1/20,000 of its original concentration of salts.