You said that I can add my goats milk into the oils instead of when I mix my lye/water solution. Will this affect the lasting quality of the soap over the old tried and true method of mixing in with the lye/water.
That is correct. You can just put the goats milk into your oils, then mix in the lye/water or put in the lye/water into the oils, then the milk, it doesn’t matter. The reason that someone originally and probably thought they had to put the milk into the lye/water, at the same time the lye/water was mixed, is because they probably considered it as part of the water. And…..they probably didn’t think past this solution since they were making small batches for friends and family.
You see, most of the early books on soapmaking were written by people making small batches without much care to production and efficiency. There was little need for a “better way”.
Some of this filters down into what I call, < Urban Legend >. One very good example of this is pouring in your lye. There is no need to dribble it in, you just dump it in. It is amazing the bad habits I run across regularly that people have passed down to others.
You can also let the lye cool down completely to almost room temperature, then add the milk. It will increase in temperature a little due to reacting with the new liquid but it won’t scald your milk. If you are doing multiple batches you can do this in the lye tank. With a little observation and note taking you will soon know exactly what temperatures you will have.
There are probably other ways to add milk that I haven’t thought of but rest assured, your soap will last just as long both ways, if everything else in the formula is just the same. The method of incorporating the milk will make no difference. Matter-of-fact, if you think about it, your milk will be going through less stress and fewer temperature changes, so your actual end product should by all rights be of higher quality.