Not only is it used in the soap making process, it's a byproduct too. Many soap manufacturers actually extract glycerin during the soap making process and reserve it for use in more expensive products. Some amount remains in every bar of soap, however, and additional may be added in order to produce a clear finish and extra moisturizing qualities. The extra also enhances the cleaning aspect of soap.
Glycerin can be dissolved easily into alcohol and water but not into oils. The pure chemical compound is called Glycerol, which indicates that it is an alcohol.
The fact that is also easily absorbs water from the surrounding air means that glycerin is hygroscopic. If some was to be left in the open, it would absorb water from the surrounding air until the liquid was eventually 20% water. A small amount placed on the tongue would cause blistering, because it is dehydrating. When beauty products containing this compound are used on skin that is well moisturized, it can help keep that moisture in.
2. Create your own pigment ink: mix gouche, which is an opaque water color, in the color you want. Add a few drops of glycerin and a splash of rubbing alcohol and spread on your ink pad. You can use water instead of the alcohol. But if the water has bacteria in it, it might result in a moldy ink pad so alcohol is better.
3. Improve acrylic paints: add a few drops of Glycerin to your rinse water when you use acrylic paints and you'll get more from your paints. It'll take longer for them to dry and it'll be easier to mix them and spread them.
4. Refill your water marker: mix Glycerin with a little water and dip the marker in it over night. The marker will absorb this liquid and be moist and ready to go again.
5. Transfer ink: add a teaspoon of glycerin to a 4oz spray bottle of water and you have dye based ink refresher, shake before using.
6. Gelli plate: I personally haven't done it but you can find lots of recipes online if you want to make your own and not buy the expensive one.
7. Revive dried up watercolors: add a few drops of glycerin to dried up watercolor paint and it will bring them back to life. This is good for the lower grade watercolors especially because the high grade colors already have glycerin in them.
8. Snow Globes: mix water and glycerin and fill a globe to make the snow fall slower.
9. Stamp cleaner: mix Glycerin, water and soap to wash your stamps and remove old dried ink from them. If you have dried rubber stamps leave them to stand with Glycerin for a few hours and it will fix the stamp.
10. Faux leather: spray paper with a mix of water and Glycerin, wrinkle and straighten back. The Glycerin will break the paper's fibers and give it a leather look.