Why are there oil spots on freshly dried clothes?
Why does ordinary shampoo sometimes clean better?
What is Soap?
What is Detergent?"
The first question is probably about the spots caused by fabric
softener, and I've come across info about that in your Fabric Care article. That article
attributes the spots to the softener sheets, but I first encountered the spots on
polyester garments in the days when I used liquid softener in my washer. Re-washing always
removed them. See (Q) and (A) below.
As for the last three, shampoo contains our friend sodium lauryl
sulfate. The soap/detergent question would be answered by the post that I agreed to send
you. A major revision of it is below. (Thanks for bringing that to the top of my "to
do" list; I should've answered long before now.)
Q & A
(Q) Why are there oil spots on freshly dried clothes?
(A) Fabric softeners, both liquid and dryer sheets, can leave greasy spots on polyester
garments. The spots can be removed by re-washing and drying without the softener. See the
article "Fabric Care" at http://www.fabrics.net/fabricca.asp.
(Q) Why does ordinary shampoo sometimes clean better?
(A) Shampoos contain detergents which are are especially good cleaners of substances which
are proteins. Hair, silk and wool are all proteins. See "Soaps and Detergents"
below.
(Q) What is Soap?
(A) See the articles "Soaps and Detergents" at ------ and "Synthetic
Surfactant or Soap?" at http://www.fabrics.net/deterg.asp
(Q) What is Detergent?
(A) See the articles "Soaps and Detergents" at ------- and "Synthetic
Surfactant or Soap?" at http://www.fabrics.net/deterg.asp
SOAPS AND DETERGENTS
A DETERGENT is a chemical compound that cleans. In the sense that a
SOAP cleans things, it can be considered a detergent. However, chemists generally make a
distinction between soaps and detergents, since soaps are salts of carboxylic acids, and
detergents are sulfate or sulfonate salts.
SOAPS
Soaps are FATTY ACID SALTS made by a reaction of fats (an animal fat
or a vegetable oil) with LYE (sodium hydroxide). SODIUM LAURATE, the sodium salt of lauric
acid, is generally considered to be one of the finest soaps.
HARD WATER (water containing the dissolved salts of calcium,
magnesium and/or iron) causes a problem: the dissolved salts combine with soap molecules
to produce a water-insoluble scum ("ring-around-the-tub"). A lot of soap is
wasted in the formation of this scum, as all of the minerals in the water have to be
removed as scum before the soap can do its cleaning work.One solution to this problem is
to wash only with distilled water, which contains no salts. This is not usually practical.
DETERGENTS
Our modern technological solution (since the 1940s) to the soap scum
problem is to use SYNTHETIC DETERGENTS which don't precipitate the mineral salts found in
hard water. Some of these synthetic detergents are chemically related to soaps, as they
are derived from the same fatty acids used to make soaps. SODIUM LAURYL SULFATE (derived
from the fatty acid lauric acid by a series of chemical reactions) is such a detergent. It
can be found in _many_ common household products. Sodium lauryl sulfate belongs to a class
of detergents referred to as "anionic." These compounds are especially effective
at cleaning fabrics that absorb water readily, such as those made of NATURAL FIBERS, such
as COTTON, WOOL AND SILK.
"ORVUS" is a commercial name for sodium lauryl sulfate. It
is available at feed stores, which sell it as a shampoo for the manes and tails of show
animals. Sodium lauryl sulfate is also packaged as a quilt soap and can be found at
suppliers of quilting products.
Sodium lauryl sulfate is a common ingredient of SHAMPOOS, and some
persons like to use shampoo for handwashing natural fibers. However, you should be aware
that shampoos may contain additional compounds which could cause undesirable results if
used for laundering fabric.
Read product labels! In the USA, ingredients are listed on labels in
order of decreasing quantities. If you use a shampoo for washing natural fibers, you want
to find ingredients that contain the chemical prefix "laur" (from lauric acid).
Myristic acid, palmitic acid, and stearic acid are also produced from fats by the action
of lye, and are considered excellent soaps. Like lauric acid, they are converted into
anionic detergents; therefore, you might also find the forms "myris,"
"palm," and "stear" among the ingredients.
The usual granular laundry detergents are sodium salts of fatty
derivatives of aromatic sulfonic acids. They are of the anionic class, with similar
cleaning properties to those of sodium lauryl sulfate. Manufacturers have now solved the
problems with biodegradability which originally plagued these types of synthetic
detergents.
Another class of detergents is referred to as
"nonanionic." These are especially good for cleaning synthetic fabrics, such as
polyesters. Most are liquids and produce little foam. You'll find them (along with anionic
detergents) in dishwashing liquids and liquid laundry detergents. The "cationic"
detergents, as well as being cleaners, also happen to be effective germicides and are used
in antiseptic soaps and mouthwashes. They're also used in fabric softeners because their
positive charges (cations) adhere to many fabrics that normally carry negative electrical
charges (anions).
In conclusion, it needs to be emphasized that no one cleaning
product is best for everything because of the chemical properties of the fabric being
cleaned, and the chemical properties of the detergent.
