So, songwinds shave soap peaked my interest and after reading a few of you wet shaver guru's posts, im thinking i am not only going to try songwinds recipe but try and make up one of my own too. Im thinking of using a naoh/koh combo. Im wondering though, and this may be irrelevat, but im a ls maker too... when calculating the recipe, how do you figure in the purity of the koh? would calculating the whole batch at a 0 sf work and just guestimate that it works out to around a 10%sf or do you guys(and gals!) still tend to calculate a sf in your split batches too?