Wednesday Wonderings: What’s the difference between BTMS-25 and BTMS-50?

In this post on turning 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…