Thursday, June 28, 2012

Question: How do oils in a serum stay combined?

In this post, Nancy asks: Okay, here goes. I feel so dumb asking this question. If you make a facial serum out of oils and extracts with vastly different specific gravity, how do they stay together without shaking, or an emulsifier? I've seen plenty of shops on Etsy selling these. I make a product, but I use Cera Bellina to hold it all together. Not a true emulsifier, but a nice product that you should get and play with. 

I make my serums creamy, not clear and just oils and oil soluble extracts. If I do that, my E settles on the bottom. It's frustrating me to pieces, cause non of them seem to have a problem, although I'm not sure I'd want to do that, mix just oils and pray the mix comes out evenly when pumped and I'd NEVER ask a customer to shake anything. GACK!!!!

How is this a stupid question? Is it opposite day? (And if it is opposite day, shouldn't we be calling it normal day?) This is a great question! But I really don't know the answer to it. You can see my bath oil above just after I made it, and it separated into different layers of the oils over time. (I didn't get a picture of this, darnit!)

I have an order with Lotioncrafter sitting at the border that contains the Cera Bellina and new emulsifiers, amongst a few other things! I can't wait to play! 

What the heck is specific gravity? It's a way of measuring if something weighs more or less than water.  Pure water at 4 Celsius is our baseline for specific gravity and everything else is compared to it. Water weighs 1000 grams per litre - 1 kg per litre - or 1 gram per millilitre. So a teaspoon or 5 ml of water weighs 5 grams. A tablespoon or 15 ml of water weighs 15 grams. A cup of water at 250 ml weighs 250 grams.

If something is listed as being less than 1, it weighs less than water per gram. If something is more than 1, it weighs more than water per gram. If something has a specific gravity of 1.03, it means it weighs 1.03 grams for every 1 millilitre or 1030 grams per litre.

Specific gravity is the reason that oil floats on top of water. A lot of the oils we use have a specific gravity of 0.90 to 0.95, which means they are lighter than water, so they float to the top of our product while the water settles on the bottom.

Let's say we make a facial serum with four oils - safflower oil (0.90), olive oil (0.91), cottonseed oil (0.88), and peanut oil (0.92), and a few oil soluble ingredients like Vitamin E (0.955) and calendula oil (0.91) they will eventually settle into layers with the heaviest oil at the bottom and the lightest oil at the top. (Order from the bottom, Vitamin E, peanut oil, calendula and olive oil, safflower oil, and cottonseed oil.)

Most of our oils are around 0.90 to 0.92, so they're really quite similar in nature, which could be one answer as to how the Etsy sellers are keeping their products together. If they use all vegetable oils and no extracts, the entire product will likely be very very close in specific gravity. Or they might be using our natural inclination to shake bottles before we use them. Or they haven't watched their product over time to see the separation. Or they don't know any better.


Mary said...

Here's an additional question: wouldn't the oils' solubility also affect the ability of a product to stay together? Would you even be able to find out that information for most oils?

p said...

Fantastic question!! I had wondered about this, but my question remained theoretical, because I've never experienced separation in any of my oil blends (except those that contain a small amount of a butter). I'm fascinated that you experienced this with a finished product, Susan!

It seems like separation must be an issue when making oil-based perfumes, because essential oils tend to have a lower specific gravity than most carrier oils (I think) - though once again, I've never encountered this problem.

Maybe as Mary asks, some oils are soluble in others, complicating a model based only on specific gravity.

Great post!

Nancy Liedel said...

I have to admit it took a lot of letting go of my ego to ask such a basic question. I was embarrassed not to know the answer, nor be able to find it on my own. I hate looking stupid. I joke a lot, but my work is something I'm very serious about.

Thank you for answering my question and not making me feel like an idiot. Which is something you'd never do. It's deeply appreciated however. Thank you so very much.

catherine said...

Hi! sells an emulsifier called lamellar maker, which it says works for water-free emulsions.

I never have used...has anyone out there tried it?

I do use their gelmaker, which works great, but web site says it's for o/w...

Stacey Neuhaus said...

Ok. I know this will sound uneducated to the more experienced lotion/serum makers....but why is it a problem to shake the product to reblend it before using it?

Jessica said...

To Stacey - I don't think it's a problem, but most people who are selling a product don't want to put "shake before using" on the label. The customer should be able to take that product and use it as-is, no prep needed. Many formulators consider it a mark of professionalism to sell a product with confidence that it will stay emulsified and act as intended. "Shake before use" directions are plentiful on salad dressings, but such labels are uncommon (and unprofessional) on personal care products!

Maybe someone who operates a business can clarify or contradict my point! I really came here to say: Susan, on the topic of facial serums, I just made one using one of your recipes as a base and it is FANTASTIC! I made it for my mom, so I used only the best stuff :) - squalene oil 30%, borage oil 30%, C12-15 alkyl brenzoate 20%, camellia oil 10%, sea buckthorn oil 10%. It's probably too expensive to be a good choice for retail sales, but I posted the percentages for anyone who wants to try it!

catherine said...

i had a 'duh!' moment on this topic. i'd made a serum just for my use with sunflower oil and some oil soluble extracts and vit e and the vit e settled in the bottom as well. i don't really care (i just shake...for myself) but this post got me thinking.

today i added a titch (don't know %) of polysorbate 80, shook it's all emulsified now! no vit e at the 11bottom.

i'd bought the polysorbate just to make water soluble oils. it hadn't occurred to me i could also use it to emulsify an all-oil serum.

just goes to show, like with the btms post, it pays to know what else you can do with an ingredient, not use it just for that one recipe you bought it for...

catherine said...

Actually my prev post ended up not being true. Although it made sense to me that poly80 would emulsify the oils after a few days there was separation.

Loz said...

Having read this blog post a while back, I've been hesitant about starting with blending facial serums (I think you can probably classify me in that Etsy seller category :). However, yesterday I blended olive oil, sunflower oil, jojoba oil, rosehip oil, avocado oil and sweet almond oil - all of which have different specific gravities. After reading this blog post, I was expecting to see at least some separation or layering but there was none. I have been standing staring at the glass in which I poured them for hours and the oils remain perfectly blended. Now admittedly essential oils would float on top and vitamin E would sink to the bottom, but the carrier oils themselves have not separated in my experiment so I question how important those specific gravities are for carrier oils that are quite similar in nature.

By the way, personally I don't think that asking someone to shake their blend before use would make that product look 'unprofessional'.

Susan Barclay-Nichols said...

Hi Loz. You wouldn't necessarily see the separation in a few hours or a day - we're talking a week or more! As for oils that are similar, if the specific gravity is different, they will separate eventually.

It's a bit like lotions. Emulsions are inherently unstable creatures, and they will come apart at some point in time. It might be today or tomorrow, it might be in twenty years, it might be in a hundred. We work hard to make sure that our emulsions are stable enough to last for a few years at least, but no matter what we do, they will separate. When it comes to combining oils, they will form layers according to their specific gravity at some point. It might be next week, it might be next year, but they will separate no matter what we do.

The essential oils might not float to the top - it depends upon their specific gravity. For instance, peppermint essential oil has a specific gravity of 0.8990 - 0.9110, so it could be the same as olive oil or calendula oil (0.91), and a product containing peppermint and those oils won't have any separation at all! Or it could be lighter than those oils and float to the top.

I wouldn't call the oils you mention similar in nature. Avocado oil and olive oil are considered medium to heavy while sunflower and sweet almond oil are considered light. Sunflower is high in linoleic acid, while avocado, olive, and sweet almond oil are high in oleic acid. Jojoba oil is technically a wax and has some funky fatty acids seen in no other oil, and rosehip oil has an interesting balance of linoleic and linolenic fatty acids. (Rosehip oil can be really bad for break out prone skin, so be wary of using it on people who have acne or roscaea!) They don't have similar fatty acid profiles, viscosity, or specific gravities.

I'm so happy to see people experimenting with chemistry! And please let me know how these experiments turn out because I'm not always right, you know!

As for shaking it, human nature seems to be we shake bottles when we pick them up, so it's not a big deal, but I don't think I'd be truly happy if I bought something from someone that required me to shake it. Because I make my own things, I know there are ways of getting those oils not to separate, so I'm extra picky, I admit that!

As a quick aside, Stacey - love the sound of that serum! And two, look for posts on cera bellina coming up today and tomorrow, if all goes well. It's awesome for making oily gels.

Nacho Liebre jr. said...

I am new to working with EO and carriers, but this post makes complete sense to me. Unless the oils are very very similar in gravity you will have separation eventually. Asking the customer to shake before every use is un professional IMO. So is there a natural solution to this issue?

Debbie Richards said...

Great Post!!! I am so excited to s all this great info.One of my goals is an eye serum :) cream @ that.thank u for all u do and share.

Susan Barclay-Nichols said...

Hi Nacho. I didn't realize I missed your question. No, there isn't a natural solution to this problem. You could, however, put it into an opaque container and they wouldn't notice it happening.