I make and love buttermilk soap also. To avoid the ammonia smell or burnt orangey color, I freeze the buttermilk solid, take the frozen buttermilk out and set to defrost a little. It’s so hot in Boston in the summer, half an hour gets it loose enough so I can slip the milk out of the container easily (I also harrass everyone I know to save 1/2 qt. containers for me). I save the container to use as a mold, lovely squarish roundish soap (because the soap bulges the container, making round soaps with corners, make sense?).
I put the frozen buttermilk into the lye liquid and wait 2 minutes till everything starts melting, then I stir, gently, gently till it’s all melted, then I put in salt and sugar, stirring to melt. The liquid becomes a dark brown, almost black, but no smell.
I make up my recipe like any other recipe, if the buttermilk isn’t enough for the liquid % of the recipe, I just add milk to make up the difference. My soap after curing 2 months is a lovely light golden color, like buttermilk. Heavenly smell, I don’t scent at all, the milky scent is great, with wild honey, whoa!!
I use buttermilk in most of my recipes. Usually, for a 12# to 13# batch of soap, I add 21 oz. of lye to 26 oz. water (depending on the oils used, of course) and add 32 oz. buttermilk at trace. I always run it through a lye calculator, so that my amounts are right. I package my lye in 21 oz. containers, so I use the oils in amounts that superfat about 6 percent, according to a lye calculator. With my soap box, that make 48 – 4 oz. bars. I used to make 12# batches, but now have expanded it a bit so that the bars are still 4 oz. after I sculpt them. I’ve also used 2% milk with a couple Tblsp. of lemon juice added to make buttermilk!
A reminder — The usual disclaimers apply. The recipes in this library reflect the individual contributors' own methods of soapmaking and are written in their own words. We cannot personally guarantee the success or results of any of the recipes included in this library.