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Glycerin is also highly "hygroscopic"
which means that it absorbs water from the air. Example: if you
left a bottle of pure glycerin exposed to air in your kitchen,
it would take moisture from the air and eventually, it would
become 80 per glycerin and 20 percent water.
Because of this hygroscopic
quality, pure, 100 percent glycerin placed on the tongue may
raise a blister, since it is dehydrating. Diluted with water,
however, it will soften your skin. (Note: While people say this
softening is the result of the glycerin attracting moisture to
your skin, there is heated debate as to whether or not the glycerin
has some other properties all its own which are helpful to the
skin. Summed up, the current thinking is "We know glycerin
softens the skin. Some people think its because it attracts moisture,
but there could be other reasons.")
Where does glycerin come from?
Up until 1889, people didn't
know how to recover glycerine from the soapmaking process, so
commercially produced glycerin mostly came from the candlemaking
industry (remember, back then candles were made from animal fats).
In 1889, a viable way to separate
the glycerin out of the soap was finally implemented. Since the
number one use of glycerin was to make nitroglycerin, which was
used to make dynamite, making soap suddenly became a lot more
profitable! I have an untested theory that you could trace the
roots of most big soapmakers (and the "fall" of the
small, local soapmaker) to about this time in history.
The process of removing the
glycerin from the soap is fairly complicated (and of course,
there are a lot of variations on the theme). In the most simplest
terms: you make soap out of fats and lye. The fats already contain
glycerin as part of their chemical makeup (both animal and vegetable
fats contain from 7% - 13% glycerine). When the fats and lye
interact, soap is formed, and the glycerin is left out as a "byproduct".
But, while it's chemically separate, it's still blended into
the soap mix.
While a cold process soapmaker
would simply pour into the molds at this stage, a commercial
soapmaker will add salt. The salt causes the soap to curdle and
float to the top. After skimming off the soap, they are left
with glycerin (and lots of "impurities" like partially
dissolved soap, extra salt, etc.). They then separate the glycerin
out by distilling it. Finally, they de-colorize the glycerin
by filtering it through charcoal, or by using some other bleaching
method.
Glycerin has lots of uses besides
being used to make nitroglycerin (note: glycerin is not an explosive
substance by itself. It has to be turned into nitroglycerin before
it becomes explosive, so it's safe to work with in your kitchen).
Some uses for glycerin include: conserving preserved fruit, as
a base for lotions, to prevent freezing in hydraulic jacks, to
lubricate molds, in some printing inks, in cake and candy making,
and (because it has an antiseptic quality) sometimes to preserve
scientific specimens in jars in your high school biology lab.
Glycerin is also used to make
clear soaps. Highly glycerinated clear soaps contain about 15%
- 20% pure glycerin. Known as "Melt and Pour" soaps,
these soaps are very easy for the hobbyist to work with. They
melt at about 160 degrees fahrenheit, and solidify fairly rapidly.
Because of their high glycerin content, the soaps are very moisturizing
to the skin. Unfortunately, this high glycerin content also means
that the soaps will dissolve more rapidly in water than soaps
with less glycerin, and that if the bar of soap is left exposed
to air, it will attract moisture and "glisten" with
beads of ambient moisture.
These downsides, however are
more than compensated by the emollient, skin loving and gentle
nature of this soap which is especially good for tender skin
and children.
(1) The pure chemical product
is called Glycerol (which shows that it is an alcohol), while
the impure commercial product is called Glycerin. This is a technical
complexity, so for this article, I'm sticking to the more familiar
term, Glycerin. |
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