Clay is an ingredient that marketers hate, formulators love, and users probably don’t think much about. If you are trying to portray your product as uniquely natural, superlatively scientific or having some kind of special ingredient with unique properties, clay isn’t really much use is it. It is hardly a charismatic material. Everyone knows what it is. There is plenty of it about. Its not really the stuff of viral marketing.
But it gets a lot more respect in the lab. You can use clay as a thickener and stabiliser in a wide range of products, as a base for mineral make up and as a way of delivering some pharmaceutical actives efficiently to the skin. But for me the most interesting use is where the clay itself is the product when it is used as the main ingredient in a mud mask. (Or, as they are very often called, a masque. Be honest- it sounds better in French doesn’t it.)
The main ingredient in a mud mask is clay – usually somewhere between 30% and 50%. Most of the rest is water. The form of clay usually used is kaolin, which is mined in quite a lot of locations around the world. It is washed using water and then dried. The properties vary from place to place. I think you get best results from kaolin mined in Cornwall, but that may simply be because that is the one I am most familiar with. You can make your own clay mask with kaolin and water if you are that way inclined.
What a clay mask does is remove oil from the skin. And if you have oily skin and have tried one, you will be able to confirm that it does this very effectively. The reason is quite interesting. If you look at a particle of kaolin under a powerful microscope you will see that it is made up of millions of tiny plates aggregated together. When preparing a clay mud mask you disperse the kaolin powder in water and apply energy to it in the form of either heat or high speed mixing – or if you want to get home in time for Eggheads both.
As the clay disperses into the water the plates separate into smaller and smaller particles, but they retain their plate like shape. As it happens, the faces of the plates tend to be negatively charged and the edges are positively charged. This has the most bizarre effect. The edge of one plate is attracted to the face of an adjacent plate. As the dispersion progresses the whole thing builds up into what has been called a ‘deck of cards’ structure.
Time for another of my famous home made illustrations.
The result of this is that a clay dispersion has a huge surface area onto which things can absorb. For instance, you can simply stir large quantities of oil into clay dispersion and it simply seems to disappear. This is how it works to soak up and remove oil or sebum from your face.
Clay mud masks with a high clay content are the ones that really clear up the grease on your skin. To my mind kaolin based ones work best, but bentonite is used in some and works well too. One grade of clay is usually labeled by its chemical name magnesium aluminium silicate, but still works well. The ones with kaolin, bentonite or magnesium aluminium silicate high up the ingredient list will be the most absorbent. Preferably they should be second place after water. There is no particular advantage to waiting for a clay mask to dry before removing it, and none at all to leaving it on once it has dried. It will only work while it is still drying. The basic colour of clay is white and it has no smell. But most formulations on sale have some colour and fragrance to make them a bit more fun, and why not?
I’d be interested to hear what other people’s experience of clay mud masks is. I don’t suffer from greasy skin myself so although I can get an idea about them I can’t fully feel their benefits.