INCI: Behentrimonium Methosulfate (and) Cetearyl Alcohol
BTMS-25 was my fav emulsifier until I used BTMS-50. Granted, I haven't had an opportunity to use every and all emulsifiers, but BTMS-25 is one that I have the least amount of problems with and it doesn't really conflict with a whole lot of other ingredients.
BTMS-25 is what is called a conditioning self emulsifier, meaning that it's supposedly powerful enough to use by itself as the only emulsifier. Its very good at keeping the oil and water from separating even if it's the only emulsifier in my experience. And it helps to condition the hair too.
The only problem I've had using BTMS-25 is when I didn't use quite enough of it (this was, of course, before I got my ingredient/kitchen scale and was relying on teaspoon/tablespoon measurements).
Being cationic, it is said to have a positive charge… which helps to attract it to the negatively charged hair. The more attracted an ingredient is, the better it conditions. By the way, some conditioners are said to have lower ph for this very reason.
It can also be used in anhydrous oil only formulas, like whipped butters, to add extra conditioning properties to it.
Recommended Usage Rate: 1 – 10%