Saturday, February 23, 2013

Weekend Wonderings: Mixing small amounts of oil with water, separation of oils in a serum, and heating and holding the phases together

In this post on witch hazel, Anonymous asks: I am working on an insect repellent using 90% Witch hazel and 10% EO. Will the two ever blend or will it have to be shaken each time?

They won't blend and they will need to be shaken every time.  Oil and water don't mix. To get them to mix, we need to add a solubilizer or emulsifier. When we make something like this spray - mostly water with a bit of oil - we add a solubilizer.

Water is polar and oil is non-polar. And in solubility, like dissolves like. Polar things dissolve or mix with polar things well, and non-polar things dissolve or mix with non-polar things well. Oil doesn't mix well with water for that reason. 

If you're curious about whether two things will mix, ask yourself a few questions. Does it seem like an oily ingredient or a watery ingredient? In which phase would we normally use them (oil or water phase)? Is there an indicator of its solubility in the name, like calling something an oil or an ester or a water soluble extract?

Consult the data sheet or supplier's website to see about its miscibility or ability to mix with other ingredients. For most ingredients, its solubility is pretty obvious. It should say "soluble in water" or "add to heated water phase" or "oil soluble". If you don't have this information, visit your supplier's site and see what they recommend. If they don't, write to them!

As a quick note, you really can't make claims about your products. You could call your product a fragrance spray - it contains essential oils - but you can't say it repel insects. Those kinds of claims require testing and you won't be able to test them. (And as someone who is a serious mosquito and biting insect magnet, I would be upset if I had a product that claimed to be an insect repellant and wasn't on my camping trips! It would ruin everything if I were to be bitten as often as those little buggers land on me.)

And I don't think 10% essential oils is recommended for a leave on product like this. I'm not an essential oils expert, but it does seem really high. (Anyone else have suggestions?

As an aside, anyone please note your name somewhere in your comments as I'm not a fan of anonymity. It adds nothing to a community, but it can seriously detract from it! Let us know who you are! 

Please visit last week's post to see more about specific solubilizers. And remember, you will have to play around with your solubilizers to see which one solubilizes the essential oils you're using. Some will work well with a 1:1 ratio, others it might take 5:1. It all depends on the essential oils!

Related posts:
Fun with chemistry: Solubility
Solubilizers: How do are they different from emulsifiers?
Esters: Using solubilizers in our products
Surfactants - fragrances & clarity
Men's products: Fragrance and body sprays

In this post, Leila Wood asks: I have made several small batches of hair serum, dimethicone and cyclomethicone based. I add about 2-3% argan oil, 0.5% vitamin E, .5% rosemary extract, and 1-2% Co2 extracts. The additives separate out of the hair serum...annoying! I look at the ingredient lists of hair serums sold at hair salons and I don't know what their trick is to keep them from separating. I understand there is an HLB system for silicones too but I am struggling to figure it out for my formulas. Any Ideas?

I address this question in this post, but the quick summary is this: Oil will form into layers if left long enough as they will have different specific gravities. The easist way to solve this problem is to capitalize upon an urge we all have when we pick up a container - shake before using!

If you aren't using water soluble ingredients, you aren't creating an emulsion, so you don't need to use an emulsifier. If you are using water soluble ingredients, you can use something like this ingredient - Lotioncrafter Serum SE - to emulsify your ingredients. You might consider doing this if you really hate the separation, but shaking it really will work well.

Again in this post, Sara writes: I'm stumped by a recent (and shocking) discovery whilst using Ecomulse in your under eye lotion formula. I've had a number of issues with Ecomulse (overcoming waxiness, cottage cheese-y emulsions etc.) and when I came across a blog that suggested heating and holding the water and oil phases TOGETHER (gasp!!), I figured what the heck, I'll give it a try. Well....it worked! I've not had a creamier final product using Ecomulse before, although I'm still trying to overcome the waxiness. Is there some reason why heating and holding the water/oil phases separately is necessary? Might this emulsion eventually break because of the phases being heated together?

Hi Sarah! How is the product doing? We'd love to hear!

I can't predict if the emulsion will break or not, but heating and holding the lotion together won't necessarily lead to a broken lotion! I know, shocking, right? I go into greater detail in this post, but the main reason we don't heat and hold the phases together is that it means the emulsifier has to do more work.

Things don't like to change their state of being unless it's easy to change - they're lazy. They hate expending energy, and will always go for the thing that makes them expend the smallest amount. When we create a lotion, we're asking our ingredients to do a lot and expend a ton of energy, which they hate doing. (This is why we heat our ingredients and mix them together. Adding heat to something generally increases solubility and it makes the molecules more energetic. And mixing means we make it easier for the ingredients to blend together.)

Separating the two phases asks less of the emulsifier, which makes the emulsion more stable. As well, heating and holding in the same container means that the emulsion can start to happen before the phase inversion temperature.

Should we add the water to the oil phase or the oil to the water phase? Yes! Either way works! Read more in this post! 

You can make lotions that don't separate by heating and holding in the same container, by not heating and holding at all, by only heating long enough to have the ingredients melt and so on, but heating and holding gives us the best odds of making a product that won't separate. And given how much work and expense it takes to make a lotion - deciding on supplies, buying supplies, waiting for supplies to come in the mail, finding a day you can get into the workshop, and so on - heating and holding for 20 minutes seems like a small annoyance to make something that is more likely to create something awesome!

Related posts:
Phase inversion
Chemistry: Anionic, cationic, and non-ionic. 
Why we heat and hold our ingredients
Why we heat and hold our ingredients separately

Do you have a Weekend Wondering? Visit this post and share! I'm going through the comments and email messages every weekend to see what interests you! 

Join me tomorrow for more Weekend Wonderings!

5 comments:

Lise M Andersen said...

Maybe the insect repellant was a room or area spray? Still, 10% is very high. 2% EO is normally considered a high dose for anything applied to the body. Add some polysorbate 20 (about 5% with 2% EO). That should keep your ingredients from separating.

Marie Z. Johansen said...
This comment has been removed by the author.
Marie Z. Johansen said...

I am redoing my comment to included a caveat.

This comment is not really about mixing oil and water, but rather about a repellent formula that really does work well. Nature's Gift Skeeter Beater. I am in no way affiliated with them, but like the EO blend. I've replicated a semblance of this formula with good results, and I DO have to shake it before each use - because water and oils surely do not mix!

Also, I'd like to thank you for your work here on this blog. I always look forward to your posts. They are always so well written, informational and instructional! Thank you !

Yvonne said...

Hi Susan,

Re: Should we add the water to the oil phase or the oil to the water phase? Yes! Either way works! Read more in this post!

When I clicked on Read more in this post! you said:

"I checked a ton of data sheets from various companies - including the data sheet on Polawax - and found nothing indicating we should be adding the water to the oil."

Copied and pasted from Polawax data sheet the following:

USAGE:
POLAWAX emulsions can be prepared easily by incorporating POLAWAX in the oil phase and then heating it and the water phase separately to 70-80°C. Once the two phases reach this temperature, the water phase is added to the oil phase in a thin stream using mechanical agitation. The emulsion is then stirred down to a temperature above the solidification point of the cream (to 30°C for a lotion). These emulsions are very stable,
easy spreading systems, but can be homogenized if desired.A preservative should always be added to protect against bacterial growth.

So it looks like they do recommend adding the water phase to the oil phase.

Sara said...

Susan,

It's been over a week now and the emulsion seems to be holding! Given your answer, I'd rather err on the side of caution and heat and hold separately. It is so cool to understand why rules of thumb...are rules of thumb (the technical aspects, anyways :)

Thanks for the in-depth and understandable explanation. You rock!

Sara