BUT you need to be extra careful. Different liquids can react to the lye differently than plain water. Also note, as the lye heats up, it will start to scorch the sugars in the milk and turn it brown and foul smelling. The good news is the smell doesn't remain in the final soap, and you can minimize the scorching with a few simple tips.
Making a lye solution with milk.
- Follow the general directions for Making Lye including all of the safety guidelines.
- Start with about 1/3 of your liquid in liquid form and the other 2/3 in slushy or frozen chunks form.
- Add the liquid 1/3 to your pitcher.
- Place your lye pitcher into the sink. Fill your sink with enough cold water and ice to almost meet the level of the milk in the pitcher. If you add too much water, your pitcher will start to float and may tip over. As you add more milk and the lye to the pitcher, you can add a bit more water and ice to the sink.
- SLOWLY add a bit of the lye to the milk. As it starts to dissolve, it will start to heat up. Stir the solution gently.
- Wait a bit more.
- Wait a bit more until the solution cools back down a bit. You don't want the solution to get much more than about 100 degrees.
- Add a bit more lye. Stir. Wait.
- Repeat, adding a bit more lye into the solution at a time, but never enough to cause the liquid to heat up considerably. As the liquid starts to heat up, add a bit of the slushy or frozen milk to the pitcher to help cool it down. (Be careful of splashing the lye solution.)
- When you're done adding all of the lye, add the remaining slushy or frozen milk and stir until everything is melted and blended.
- Take notes!
NOTE--Don't leave your lye pitcher unattended while it's cooling in the sink if there is any chance of a pet, child or spouse inadvertently tipping it over or, worse yet, getting into it.
Past that, the procedure works just the same as mixing lye with plain water. Be safe. Enjoy the experimentation!