Next time you are in the grocery store buying a 6 pack of bath bars, have a look at the label. Does it say “soap” anywhere? Some do, but some do not.
Why does it matter? Because soap is the cleaner meant for human skin. Do you clean your dishes with carpet cleaner? Do you wash clothes with toilet bowl cleaner? No. Different surfaces and materials require different cleansers.
So what are bath bars?
Products marked as “bath bars” (with no mention of “soap” in sight) that are very inexpensive are usually blocks of detergent. Yep, like the one in your laundry cupboard. Heck, some manufacturers actually give instructions how to turn their bath bar INTO laundry detergent – like that is a GOOD thing!
Some bath bars started life out as regular soap, but then are processed until they are no longer recognizable as actual soap. That is when additives are introduced to make up for the fact that this cleansing bar would be far too harsh on its own. And again, these additives are touted as advantages of the product.
All cleansers share some like-minded chemistry. The basic theory is the combination of a certain cleanser and water will remove unwanted substances. Water washes away any water soluble material, and the cleanser is formulated to remove the dirt that is not water soluble, but is also not the surface of the object being cleaned.
All cleansers will clean using a “surfactant” action – which means reducing the stick-together power of the particles it encounters. The question is: how harshly, how effectively, and with what side effects? The ingredients used to make the cleanser determine the degree of stripping, what kinds of dirt it will attract, and the impact on the surface being cleaned.
When it comes to complex surfaces like human skin, there is a bit of an art to predicting what needs to be “removed”. Skin is made of some of the same substances as the kinds of dirt we humans get into. We also consider the normal by products of our body’s functioning to be “dirt”. A skin cleanser must be effective at removing the materials that are waste without stripping the actual skin.
Real soap made with a strong base (lye) combined with carbon based fatty acids (vegetable oils and animal fats) is a cleanser that is strong enough to remove the unwanted materials found on humans without damaging the skin itself.
Isn’t Lye Soap Harsh?
Lye soap with too much lye is indeed quite harsh. Prior to the days of precise chemistry, the process of creating lye for soapmaking had a lot of variables. It is very hard to produce an accurate measure of the concentration of lye in a solution without modern scientific methods. Today we have confidence that our lye amounts are correct and our recipes produce gentle products.