Glycerin has been used for many things including bombs like TNT but I guess it can be used for making soap. (or I am sure they use glycerin to make commercial soap too)
Here’s a quick way to make some natural soap from glycerin:
Use a 6-quart slow cooker. Do not put the soap mold into your stoneware and add glycerin cubes, and turn it on. The mold will melt. And you will be annoyed when your husband says something along the lines of ‘I thought that might happen.’
What you should do instead is put an oven-safe dish (or two) into your stoneware and add the separated blocks. Cover and cook on high for about 1 hour, or until the glycerin is all liquidy. Using oven mitts (trust me), carefully pour liquid glycerin into each mold. Add fragrance and color. A bit of fragrance goes a long way, but you do need quite a few drops of color. Stir with a skewer. Let soap cure for about 1 hour before removing from the form. If you wait until it’s fully cool, it pops out of the mold much more easily than if you try to rush it. Repeat steps until you run out of glycerin.
I guess this recipe is an excerpt from the book Make It Fast, Cook It Slow, perhaps you can get it for more cool DIY ideas for your home. (or perhaps on slow cooking more or less)