Silica – The Substance of Sand
I’ve been talking about Silica a lot this week, I don’t know why but some weeks are like that, everybody needs the same thing. Must be something in the air.
Anyway, one of the main questions I get is ‘is the silica natural?’
So I thought I’d best tell everyone.
But before I do that I’ll tell you what it is and what it does in living things and in a cosmetic.
What is it?
Silica = Silicon Dioxide (SiO2)
Silicon = A metalloid element in the periodic table. Naturally occurring
Silicone = Polymers (large chemicals made up from repeating units) based on siloxanes. Siloxanes are chemicals that have O-Si-O bonds holding them together.
Silica In living things.
Plants and animals need Silica for tissue building and strengthening. Plants tend to get their silica from the soil in the form of Mono Silicic Acids. Animals tend to get their silica from eating plants, either directly or indirectly (by eating other animals). In plants the silica has been found to improve drought tolerance and improve tissue strength. In animals silica has a role in collagen production as well as our general growth and development. Because of silica’s role in collagen production some skin care brands add silica into their formulations to boost collagen but generally speaking we get more than enough usable silica from our diet.
In a cosmetic formula
We generally add silica to improve the structure of our products. Silica can be used as a thickener and stabilising agent in many different types of formulations from lipsticks to toothpaste, moisturisers to shower gels. It can decrease the greasiness of a formula and can even increase a products SPF in some cases as some grades of silica improve wash-off and sweat resistance.
So is this magical ingredient natural?
Silica is the common name given to silicon dioxide SiO2. However, that is a bit confusing because while we write SiO2 for the molecular structure of silica, it is energetically unfavourable for it to exist like this, instead Silica tends to exist as SiO4 in a mesh with some other silica friends in a network that works out as having an average of one Silicon to two oxygens in the structure hence the SiO2 moniker.
Silicone dioxide occurs naturally on this planet and is most often found bound up in Quartz which looks like this:
However, the silica in Quartz is of little use to the cosmetic chemist like this as it is bound up by four oxygens in a hard crystaline maize that has none of the properties we are seeking. Liberating it takes a little bit of chemistry.
Sand contains lots of quartz and is the cheapest way to get little bits of quartz for turning into silica.
Sand is burned with coal and an iron catalyst and turned into an intermediate chemical called ferrosilicon, this ferrosilicon is then reacted into silicon tetrachloride and then again onto silica. So, harvesting silica from sand takes two intermediate steps. This is carried out on an industrial scale thus making the resulting silica Synthetically produced.
And the result of all of that is….
Well to be honest the results can and do vary considerably from manufacturer to manufacturer, product grade to product grade. However, the basic ‘thing’ that is produced is a Silica (SiO2) polymer bound in an irregular style that prevents crystalisation. So you might be wondering why scientists go to so much effort to break something then re-make it almost the same as before? Well what results is different in structure, not chemistry – in the same way that you might use the same Lego bricks to build a house or a series of small block stacks. It might be easier to think of this as producing silica block stacks.
So it’s synthetic?
Well yes but the fact of the matter is all silica (SiO2) is synthetic in as much as while yes, silica does occur in nature, there is nowhere in nature that you can just go and pick some usable stuff up and pop it into your cosmetic unless you really want a quartz or sand infused moisturiser.
Can it be used in natural products?
Because this is a mineral based ingredient it kind of comes under the same ‘grey’ area as synthetic iron oxide pigments and synthetic mica. All manufactured, all ‘chemically processed’ and yet all nature-identical. Further, as there is no viable non-interfered with alternative there is no choice to use anything other than silica that has undergone chemical processing. The type of silica I talk about here is accepted under various organic legislation as a viable input for farmers and I would say that if it is good enough for them, it is good enough for my organic or natural minded cosmetic brand owners.
OK so remind me of why I need this in my life again?
Thickening oils, stabilising cosmetic emulsions, reducing the greasy feeling, improving wash-resistance (long-wear cosmetics) and much more.
Any down sides?
Yes. The silica particles I talk about are nanoparticle sized. That means care must be taken when handling this material as it represents a breathing hazard. Once wetted and in a product silica is perfectly safe and as I said, this stuff is added direct to soil where it helps to feed plants and animals alike.
So that’s all folks.