conditioner bars into shaving bars, Melanie asks, What is the difference in usage between BTMS and BTMS-50? I see that BTMS-50 includes Butylene Glycol, but how do I choose between these two when making a shaving bar? (or anything else for that matter)
From this post, how to use BTMS-25 in place of BTMS-50:
What's the difference between BTMS-25 and BTMS-50?
Incroquat BTMS-50 is behentrimonium methosulfate (and) cetyl alcohol (and) butylene glycol. It has 50% behentrimonium methosulfate, the active ingredient for conditioning our hair, the cationic quaternary compound. It contains cetyl alcohol to boost the substantivity of the conditioner, and butylene glycol as a humectant.
BTMS-25 (sometimes found as Rita BTMS-225) is Behentrimonium Methosulfate (and) Cetearyl Alcohol. It has 25% behentrimonium methosulfate. It contains cetearyl alcohol to boost the substantivity of the conditioner. It does not contain a humectant. The cetearyl alcohol may feel a little waxier to some people.
How to use BTMS-25 in a conditioner recipe that calls for BTMS-50?
If your goal is to get the same amount of behentrimonium methosulfate in the product, then it seems logical to suggest that you would want to use double the amount of BTMS-25. A recipe that calls for 8% BTMS-50 would require 16% BTMS-25...but I think you'd end up with something with a balm consistency instead of a liquid conditioner, so I'm not totally comfortable recommending this. Instead, I recommend making the recipe how it is written, and seeing how you like it.
To answer your question, in the case of a shaving bar or conditioner bar, you can use either version. If you use the BTMS-25, you'll get something a little more waxy feeling thanks to the cetearyl alcohol. If you use the BTMS-50, you'll get something a little slicker feeling thanks to the cetyl alcohol. In a shaving bar, the difference will be minor.
What's the difference on my hair between BTMS-50 and BTMS-25?
BTMS-25 and products not emulsifying
Substituting BTMS-25 for BTMS-50 in lotion recipes
How much cetyl alcohol to use with BTMS-25?
Substitutions: What to do when you can't wait to create!