Attributes of a Cosmetic emulsion
Every cream we use creates a different skin feel. Each one of them has a different consistency and different color, different glossiness, and different transparency. All these attributes aren’t just a coincidence thrown together in a product. They appear because a cosmetic scientist wanted the cream to be exactly like this. Exactly this skin feel this consistency, this color, this glossiness and this transparency.
There are several different ingredients in a cream and each one of them has an impact on these attributes. So it is the talent of a cosmetic scientist to know the behavior of the ingredients very well in order to estimate their impact on the whole system. But first things first – let’s have a look at what the basic ingredients of a cream are.
A cream is usually called „emulsion“ in cosmetic-scientist-language. We also know other emulsions in our day to day life. The most common examples of emulsions are milk, mayonnaise, and salad sauce. So what makes an emulsion an emulsion?
Every emulsion consists of two main phases. One is the water phase and the other is the oil phase. They are not really mixable just like this and will always separate. So the third very important part is the emulsifier. The emulsifier makes the two phases stick together. In mayonnaise, for example, the emulsifier is the natural lecithin from the egg yolk. Other ingredients that you will find in a cosmetic emulsion are preservatives, active ingredients, and fragrances.
The Emulsions heart of heart
In order for the two phases to stick together, they have to be „dispersed“ in one another. Dispersed means that one phase builds small droplets within the other phase. The dispersed phase is also called the „inner phase“ while the other phase is called the „outer phase“. A typical cream we know is an „oil in water“ emulsion (O/W). This means that the oil phase is the inner phase (droplets) and the water phase is surrounding the oil phase as the outer phase. The opposite of this is a „water in oil“ emulsion (W/O). W/O emulsions are very rich and hard to wash off. This comes in handy when we want a cream to stick for example to a sweet little baby bottom to protect the delicate skin there.
The main thing that stabilizes the droplets of the inner phase is the emulsifier. Emulsifiers are a bit undecided if you will. One part of the emulsifier molecule loves the water while the other part loves the oil. This leads the emulsifier to be the connecting part between the two phases with one part hanging out in the water phase and the other part chilling in the oil phase. Through the chosen emulsifier you can either create an O/W or a W/O emulsion. The emulsifier also has a big impact on the skin feel, the consistency and the transparency of an emulsion. This is because all these attributes are influenced by droplet size and arrangement.
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