Saturday, June 24, 2017

Weekend Wonderings: Can when and how we mix have an impact on an emulsion?

In this post, Weekend Wonderings, Melinda says: I had something interesting happen when I used BTMS 25 in my lotion. In my first batch of lotion this week, I accidentally let the temperature to both water and oil get down to 45˚C. When I added the water to the oil, it immediately thickened up to a cool whip consistency. I stick blended, then added preservative and FO. 

In my subsequent batches, I mixed water to oil at the proper temperature. I find it interesting that all have the exact same ingredients and percentages yet the first emulsion seems thicker and waxier while the others feel more water-based if I could use that term. Do you think that the mix at improper temp will effect the overall integrity of the product?

I promise we'll get to the answer to your question eventually, but I need to beg your indulgence to write about something that might not seem related for a bit...

I had a great time teaching my conditioner class at Windy Point Soap in Calgary, but for some strange reason the leave in - which I've made and taught more than a hundred times, not exaggerating, I swear - separated for two of the three groups. We were using the same ingredients I use at home, but no luck. They started the recipe again, and one of the two groups separated again! ARGH! What the heck was going on?

There was one difference that I didn't think would be a big deal: We were using stick blenders. At home and when I teach at Voyageur Soap & Candle, we use hand mixers. As a non-soaper, I rarely use a stick blender. Because I wanted to make whipped butter when I started this amazing adventure, I bought a Black & Decker hand mixer with a whisk attachment and that type of appliance is what I continue to use for almost every product I make.

It's all about shear! A stick blender is a "high shear" mixer, one that "disperses, or transports, one phase or ingredient (liquid, solid, gas) into a main continuous phase (liquid), with which it would normally be immiscible." (Wikipedia). The water part of our emulsions are considered the external or continuous phase of the product, so a high shear mixer would mix the oil and water to create an emulsion. (When it brings liquid and liquid together, it's an emulsion. Solid into liquid is a suspension.)

Related post: The Bancroft rule

If we consider that the shear rate of our mixture is defined as the "relative motion between adjacent layers of a moving liquid", then something that is high shear will brings those layers together quicker than something that is low shear. A high shear mixer will disperse one phase of our recipe into a phase into which it wouldn't normally avoid mixing. High shear mixers spin quick in the middle than the outsides, and this difference creates the high shear. Immersion or stick blenders and food processors are high shear mixers.

For something like gums or polymers, we want low shear mixers, which are designed to move the ingredients around with a low amount of energy. Gums and polymers are called non-Newtonian fluids, meaning they change in viscosity according to shear. Ketchup is a great example of this: It's thick and sticky and won't move until you hit the bottle, then it turns liquid and flows!

I like hand mixers, which are also low shear mixers, and most of my recipes are mixed with one of these.

Don't worry...I'm almost at the main point of all of this...

In my instructions for the class, I didn't say how long the participants should mix their conditioners, and it was such a chaotic and fun class, I didn't get around to some of the tables to give them the information that they should mix for a few minutes, then stop and do something else as the product cooled to the point when they could add their preservative and fragrance/essential oils. So they stick blended the product for quite some time, which lead to the emulsion failing!

How interesting is that? (Well, I find it interesting!)

To return to the original question, "Do you think that the mix at improper temp will effect the overall integrity of the product?"

Totally! How and when we mix can have a huge impact on what we make! I tested this out a few years ago by making two lotions, one mixed with the hand mixer beater attachment, the other with the whisk. The latter was a whippy, fluffy, mousse-like concoction compared to the regular lotion kind of consistency with the beater.

Certain emulsifiers demand specific types of mixing. Simulgreen 18-2 and Montanov 68 need us to use a stick blender to start, then a hand mixer (lower shear) when they start to cool down. Olivem 1000 is very sensitive to mixing, too.

I will be writing about Simulgreen 18-2 soon! There are just so many things to write about and not enough time!!! 

Having said all of this, the data sheets for Incroquat BTMS-50 note that we want to add the water and oil phases together at 75˚C to 80˚C, so for the best results, this is what we should be doing. So the official answer is yes, mixing them together at a low temperature may result in a less than optimal product. (Who among us is always perfect when we make products, right?)

I know, I know, I do go on about things that I think are interesting, so if you've skipped to the bottom to see the short answer it is this - yes, I think mixing at improper temperatures can have an impact on the integrity of the product.


Cary@ luxe labs said...

For high shear mixing to be truly effective in reducing particle size which increases stability then it really should be done when the emulsion is relatively thin viscosity wise which usually means when it is still hot. Once it starts to thicken too much on cooldown it is less effective. Cooldown mixing is usually best with low shear continuous mixing. That's my experience anyway. Love your blog such a great resource

PamBirtolo said...

Hey Sue,
Since I've been following you, a very long time, I have always used a stick blender in all of your emulsion recipes. I'm trying to think what I may do differently that makes your formulas work for me. Lots of times, I mix a litte, put in fridg a bit and finish mixing. Wonder if that is why they work? Anyway, fascinating post.
Take care

Susanna Originals said...

Your timing is impeccable; you're giving me the answer to something before I even realized there was a question. I made a huge batch of my hand cream yesterday and did two things differently. Firstly, the batch was so big that I poured the oil mixture into a large stainless steel bowl. Which would cool it faster because my kitchen is cool. And just when I started mixing with my stick blender, it broke, so I continued with my hand mixer. Made great froth! I ended up with a much lighter, fluffy batch of cream. My recipe uses polawax and is mostly coconut oil so it's usually quite firm.

Elizabeth Sauls said...

I am a soaper, so naturally I used my stick blender when I moved into the land of non-soapy formulating. I've been using my stick blender for emulsions Long before I found your wonderful blog. I have had trouble with Gels not consistently working for me and this is probably the likely reason. Thank you for all that you write. You have opened up a whole new world of exciting ingredients that I had no idea what to do with.