Selecting a facial cleanser, starting from recognizing surfactants
A few days ago, a good friend of a sensitive skin girl, due to the use of inappropriate cleanser, resulting in worse skin conditions, so this time to talk about how to pick the right cleanser for you.
The main role of the cleanser is to clean, do not expect too much whitening and hydration effect, in a good completion of the work of cleaning at the same time, to the skin to bring the lowest burden, it should be the appeal of the cleanser. The main component responsible for the cleansing effect in the facial cleanser is the surfactant. Therefore, the surfactants in the formula are the key to whether the cleanser is suitable for you or not. Therefore, let’s start with surfactants to help you pick the right face wash.
I. Soap-based / soap-based surfactants
When I was in high school, I didn’t have many opportunities to take chemistry lab classes, and I believe that we all still remember the little experiment of “making soap (saponification reaction)”. Oil and lye are heated and stirred to produce high fatty acid salts (soap) and glycerol, and finally, through salt precipitation, the soap is formed into a block.
Why mention this? Because science and technology are always developing gradually, and nowadays, although it’s not common to use soap to wash your face, the cleaning principle of soap is still used in facial cleansers, which is one of the types of facial cleansers – soap-based facial cleansers.
The advantage of soap-based cleansers is that they have a strong cleansing ability, but the disadvantage is that they have a high pH (pH 8.5~9.5) and are more irritating than other types of cleansers, so they are better suited for oily skin without wounds. Dry skin, on the other hand, will damage the stratum corneum if it is over-cleaned due to insufficient surface sebum, so soap-based cleansers are not suitable for dry or dryish skin.
So how do you tell if it’s a soap-based cleanser from the formula?
As we know from our little high school soap making experiment, there are two keys to making soap: fatty acids and lye.
The fatty acids commonly used in formulations are: lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), and so forth.
What do these dodecanoic, tetradecanoic, hexadecanoic, and octadecanoic acids mean? It means the number of carbon atoms in the carbon chain. The higher the number, the finer and more stable the foam, and the lower the skin irritation. In other words, the highest skin irritant is lauric acid and the weakest is stearic acid. Also, did you notice that the number of carbon atoms are all even? That’s because fatty acids in nature almost always have an even number of carbon atoms; odd numbers are rare.
What about the bases, most of which are potassium hydroxide, sodium hydroxide, triethanolamine (TEA), etc.?
If both fatty acids and bases appear in the ingredient list, it’s a soap-based formula.
However, sometimes the fatty acids and bases do not appear in the formula as they are, but rather as their children, the higher fatty acid salts, which are the soaps themselves. For example: sodium/potassium laurate, sodium/potassium myristate, sodium/potassium stearate, etc. These are soap-based surfactants, which are surfactants that are created during the reaction process.
