Sunday, June 23, 2013

Weekend Wonderings: Using salicylic acid without alcohol and making a face cream absorb better

In the Weekend Wondering post, Topher asks: I want to create a 2% salicylic acid toner without alcohol. I noticed that in your toner recipes you do not use alcohol, yet the SA is completely dissolved. How do you do this? 

To be honest, I use white willow bark most of the time because I don't like having to use alcohol to dissolve salicylic acid. (Nothing against alcohol, but my skin doesn't like it.) And to be more honest, it can precipitate out over time, but I'm not that worried about it because I can shake it up and use it that way. (One of the bonuses of not making products for sale!)

Having said this, we can dissolve it in other alcohols, like the polyalcohols we find as glycerin. (Many of our humectants are polyalcohols.) Salicylic acid dissolves better in warmer water, but it can precipitate when the toner cools down, so it's not as sure a method as using alcohols.

If you're referring to this toner (Min-maxing your toner), you can see I'm using an emulsifier in the form of Caprol Micro Express, which helped the salicylic acid remain suspended instead of precipitating. 

This is a great chart on how we can dissolve salicylic acid with other things. Emulsifiers, polyalcohols, and alcohols all increase the solubility of salicylic acid in water. Also check out this link on using these methods to dissolve it. 

In the same Weekend Wondering post, Irish Molly asks: I was wondering something I am making a face cream and my skin really likes coconut oil but it does not absorb very quickly, I was wondering if I pair it with another oil that does absorb quicker into my skin if everything would absorb quicker or would it make the other oil absorb slower, or would it meet somewhere in the middle, I guess to sum it up, when combining 2 or more oils what happens with the absorption, does it go with the quickest absorbing or the slowest, what exactly happens in the process of combining and what happens with the efficacy rate of thee singular oil when combined (Example: combining avocado and coconut oil would they lose anything as far as their benefits when put together)

When asking this question, there are a few things we can consider. Do we want to increase the possibility of absorption or create the sensation of absorption?

We can use things called penetration enhancers to alter the nature of the stratum corneum and allow things to be absorbed that wouldn't normally be absorbed. For instance, adding something like propylene glycol or SLS to a product will "...reversibly decrease the barrier resistance of the stratum corneum and allow drugs to penetrate more readily to the viable tissues and the systemic circulation." (Read the linked post for more on this topic...) But how do we know how much we've increased the permeability and such? It seems easier to work on the idea of creating the sensation of absorption.

Most of the stuff we put on our skin isn't absorbed - the molecules are too big and our skin is way too good at protecting us from the outside world - and we generally have to make an effort for it to be absorbed. Instead, what we seek is the sensation we call absorption, which seems to be the idea that a product feels less greasy a few minutes after application and eventually seems to disappear. We can attain this sensation this by adding things that make the product feel less greasy. An easy way to do this is to make an anhydrous product into a lotion, so you'd incorporate the coconut oil into your face cream and it will feel less greasy than it does on its own. Any oil on its own will always feel more greasy than using it in a lotion.

When making a lotion or an anhydrous product, you could combine it with a less greasy feeling oil, like hazelnut oil or macadamia nut oil, or you could use an ester like isopropyl myristate (IPM) or isopropyl palmitate (IPP) (both of which are penetration enhancers as well). In a lotion, consider using astringent feeling butters - like mango butter - or astringent feeling liquids - like witch hazel, aloe vera, and some hydrosols. And finally, consider using a drier feeling emulsifier like Incroquat BTMS-50 or Ritamulse SCG instead of e-wax or Polawax.

Coconut oil is never going to feel non-greasy because it is a greasy feeling oil. You could also substitute something like fractionated coconut oil for it, which is a very light feeling, dry-ish feeling oil. But having said this, the feeling of greasiness on your skin doesn't mean you aren't getting the goodness from it. It is still offering emolliency, occlusion, and a reduction in transepidermal water loss, as well as all those lovely polyphenols!

Combining the oils will not negate the awesome power of another oil, so you can create any combinations you wish and still get the things you like about each. And you can't increase or decrease the absorption of another oil by combining them as they really aren't absorbing into your skin, but you can increase the sensation of absorption as I note above. (There are exceptions, as there always are...)

Related posts:
Astringents - are they moisturizing?
Let's talk about drier feeling oils
Products for men (an emphasis on drier and more powdery feeling products)

Have a question? Comment on a post or visit the Weekend Wonderings post and ask away!


melian1 said...
This comment has been removed by the author.
melian1 said...
This comment has been removed by the author.
Bh Kk said...

Hi Susan
Thanks for such an informative post. Do please tell us also about the "exceptions" you mentioned in this blog post.

p said...

Great post as always, Susan! I love hearing your response to basic musings like Irish Molly's. Related question: do you have any idea why is it that coconut oil alone feels greasier than coconut oil in a lotion?

I've noticed this as well, and for a while I attributed it simply to quantity. I.e. even if you're trying to use very little straight coconut oil, you still will probably end up getting more coconut oil on your skin than if you use a coconut oil lotion... but really that doesn't seem right to me.


Anonymous said...

So, if I'm making a 3% solution and salicylic acid is not entirely dissolved (because I'm not using the right ingredients), does it mean that your skin is not actually exposed to the full 3% of SA? I'm a little confused about a solubility number. If a 40% SA has a solubility of 1.592 in Propylene glycol, what does that mean?