Everyone has there own special way to make a milk soap. If the milk gets to hot, it will turn orange and have an odd smell. I found that the best way is by freezing the milk. I usually freeze in ice cube trays. Each cube is one ounce, so it makes measuring easy. I replace all of the water with the milk.
The most important thing to remember is to add the lye very slowly. I usually only add one spoonful at a time, stir, then wait about one to two minutes before adding another spoonful. In between stirs, I will get the oils melted. This gives the oil time to cool down to room temperature.
If I time it right, all the milk cubes will be melted by the time the last of lye is added.
I do not insulate this soap and place it the refrigerator overnight. Let it sit at room temperature overnight before cutting.