So, I would never let a classroom of 6th and 7th graders do this. In fact, I did this experiment as a demonstration once in my 9th grade classroom and it went terribly wrong without injuring anyone. I learned SO much that time. And now, I'm letting my kids make soap. We used the same cold process that I've used about 6 times with my dad to make soap. This experiment tied in math, science and history because the kids had to research how early soap makers did this without the local hardware store bottle of 100 percent lye. We did indoor work and outdoor work, but had our safety goggles and masks on the whole time. They never got close enough to the actual chemicals for the need of gloves. Another good reason for this experiment in the Logic Stage of learning is for them to understand the dangers and necessity for safety.In the first picture you can see the kids in their masks and goggles writing up the experiment with the necessary Scientific Method while I made measurements on the scale.
In the second picture you can see we've moved outside to mix the water into the lye (NaOH) container and record the exothermic reaction with a probe thermometer covered by a plastic bag.
We moved back inside to measure the lard (fats) and prepare to mix with the lye/water. In the third picture you can see the finished written exercise and the soap poured into cute molds and a big bar in the round yogurt container for Grampa's Christmas present. These will cure for 4-6 weeks on our side table in the dining room so we can continually monitor the process.
liquid obtained by bleaching wood ashes (KOH vs NaOH)