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Soaps,
Shampoo And Detergents
What’s The Difference Between Various
Types Of Soaps, Shampoo And Detergents?
Ashish
Back in the days of our ancestors – who lived as hunter-gatherers
and had to toil to get something to eat – I believe that people paid less
attention to how they washed their hair or hands than they did to avoiding
getting eaten alive by a wild beast.
However, the people of the 21st century are spoilt for choices when it
comes to choosing the best product for personal hygiene.
You have soaps to bathe with, shampoos to clean your hair, detergents to wash your
clothes with and so on. Yet if all of these products are essentially soaps,
what’s the difference between them?
How are
various types of soaps different from each other?
What is a soap?
We all know and identify a soap as something that helps us wash stuff,
but what actually is a soap? What is its chemical definition?
A soap, in
essence, is the salt of a fatty acid.
A soap molecule consists of a polar ionic hydrophilic end
(“water-loving” end) and a nonpolar, hydrophobic end (“water-hating” end).
When soap is mixed with water, its molecules arrange themselves in the
form of roughly spherical aggregates of 60 or so molecules.
‘True’ soaps are produced by mixing animal fats or vegetable fats with
a strongly alkaline solution, such as lye (usually sodium hydroxide) or potash
(fertilizer potassium).
As such, from a purely technical standpoint, most modern liquid soaps
are not actually soaps.
Different types of soaps
Technically speaking, most modern soaps are not really soaps. They are
usually mixtures of petroleum-derived surfactants (e.g., sodium lauryl sulfate)
with other chemicals that produce detergents matching the desired use.
Depending on the type of chemicals you use, you can get very different
types of soaps. For instance, using potash will yield a liquid soap, while
lye will form a hard soap, like what you get in the shape of bars.
The other factor that matters is the fat you use while making these
soaps; olive oil makes a very soft soap, while lye makes a very hard and dry
bar of soap.
It must be noted that all detergents – regardless of what they’re
used on (e.g., hair, hands, clothes, dishes etc.) work on the same basic
principle: they break up oils and dirt and wash them away with the help of
water.
Thus, as far as their general purpose is concerned, all soaps are technically pretty much the same.
However, it’s also true that different products are suited for
different conditions, and therefore cannot be used interchangeably.
For instance, you wouldn’t want to wash your hair with the soap that
you use in your washing machine, would you?
Below are a few common types and forms of soaps:
Shampoo
A shampoo is usually made by combining a surfactant (generally sodium
lauryl sulfate or sodium laureth sulfate) with a co-surfactant (usually
cocamidopropyl betaine) in water to form a thick, viscous liquid.
It’s designed to be gentle on keratin (a fibrous protein important for
hair formation).
Shampoo is also able to rinse out from the hair quickly, thanks to its
fairly low concentration of surfactants.
Hand and body wash soaps
These soaps are typically formed with a mild surfactant to avoid
irritation of the skin, and they have a bunch of other ingredients that
have a few added benefits, such as adding a pleasant smell, moisturizing
the skin, improving lather etc.
Hand washes are also typically less foamy, since they don’t need to
cover very much surface area and are not used as frequently. These soaps are also more concentrated than shampoo.
Face washes have even more specialized ingredients, such as ceramides
and multivesicular emulsions, alpha hydroxy acids, benzoyl peroxide or
salicylic acid, etc. which, in addition to keeping the face clean, also help to
fight conditions like acne.
Bar soaps
Bar soaps are the closest thing we have to the ‘true’ kind of soap,
i.e., they are formed with animal fats or plant oils and caustic soda (sodium
hydroxide, which is a strong alkaline substance).
In addition to the basic ingredients, which remain pretty consistent
in all bar soaps, they may have added ingredients to enhance the color, texture
and scent.
Laundry detergents
Laundry detergents are highly concentrated (unlike shampoos and body
wash soaps), as they are used only after getting diluted by large amounts of
‘wash water’.
That’s why it’s such a task to rinse off even a few drops of liquid
detergent on your hands (because they are so concentrated).
They contain certain surfactants that can work with both cold or hard
water (as these surfactants are less susceptible to water hardness), which is
why they are much better at washing clothes than your run-of-the-mill bar soap.
Traditional washing powders are usually of a higher pH than liquid
detergents, which are closer to a neutral pH.
Dishwashing detergents
Dishwashing detergents that are used with hands directly must
remove dirt, grease, sugar etc. from dishes without being too harsh on the
skin.
That’s why they don’t contain bleach, and instead use a mixture of
surfactants that work near neutral pH and are mild on the skin.
Dishwashing detergents used in automatic dishwashers,
on the other hand, don’t care about being gently towards your skin, as they
don’t usually come in direct contact with your skin or any organic fibers.
As such, these detergents can and do use much harsher ingredients,
which often include abrasives.
In short, they rely on a brute-force approach by breaking down food
and stains with high pH and chlorine bleach, but would be quite harsh to the
skin if they came in contact with your hands.
Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.
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Hand and body wash soaps are usually made with
mild surfactants so they don’t dry out the skin
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Bar soaps are quite common, but they are
effective in a very narrow range of environments
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Washing powders are usually of higher pH than
liquid detergents for laundry
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