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.
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.
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.