Glycerin is the other thing you get when oils turn into soap. It is a clear, thick liquid that attracts and holds water, and it is also produced separately for use on its own. In our Solid Coconut Soap Dish Bar it works as a humectant, holding a little water in the bar so it does not dry out between uses. What it does not do is clean.
Quick facts
- What it is: A humectant, also called glycerol. Technical name: 1,2,3-propanetriol.
- Its job in our products: Holds water in the bar so it does not dry out between uses.
- Where it comes from: It forms when fats and oils are turned into soap, and it is also refined and sold on its own.
- Smell: None of its own (PubChem describes it as odorless).
- EPA Safer Choice: Green circle, listed as glycerol.
- EWG grade: A. See the EWG entry.
- CAS number: 56-81-5
Why it holds on to water
Glycerin is a small molecule with three hydroxyl (OH) groups, one on each of its three carbon atoms. Each of those groups forms hydrogen bonds with water, which is why glycerin pulls moisture from the air and holds on to it. That property is what makes it a humectant.
A soap bar gets wet and then dries out over and over. Glycerin holds on to some of that water, so the bar is less likely to dry out between uses. Letting it drain on a soap dish keeps it from going soft. Glycerin is not a surfactant and does no grease cutting. That job belongs to the soap, sodium cocoate. For another water-loving ingredient with a structural job, see sorbitol in our refill tablets.
Where it comes from
Glycerin is the backbone of the triglycerides that make up fats and oils. In saponification, the reaction that turns oils into soap, each triglyceride splits into one glycerin molecule and three soap molecules. That is why glycerin and soap so often appear together on a soap bar's label.
Ratings, and what happens down the drain
EPA lists it, as glycerol, with a green circle, and EWG grades it A. Our page on how we vet ingredients explains what those ratings mean.
Microbes break glycerin down in soil and water. In the standard Japanese MITI test with activated sludge, it reached 63% of its theoretical oxygen demand (the oxygen needed to break it down completely) within two weeks, and NIH's PubChem summary concludes that biodegradation is an important fate process for it in soil and water. Its estimated bioconcentration factor of 3 means it has low potential to build up in fish.
The U.S. Food and Drug Administration lists glycerin as generally recognized as safe (GRAS) for food use under 21 CFR 182.1320. That status covers food, not cleaning products, and our bar is not food.
Handling and safety
Pure glycerin can mildly irritate eyes. The bigger thing to note is the soap around it: soap is alkaline, so the bar can dry or irritate skin for some people and can irritate eyes.
The glycerin is there for the bar, not as a skin treatment. It mixes completely with water, so it rinses off with the soap. Use the bar as directed. If soap gets in eyes, rinse cautiously with water for several minutes. If any is swallowed, call Poison Help at 1-800-222-1222, free and open 24 hours a day. Keep all cleaning products out of reach of children and pets.
Which Green Llama products use it
- Solid Coconut Soap Dish Bar
- Dish Washing Starter Pack
- Expert Home Cleaner Kit (includes scented sprays)
- Home Kitchen Kit (fragrance-free)
- Dish Starter Kit (fragrance-free)
Full ingredient lists are on each product page. Or browse all our ingredients →
Sources
- America's Poison Centers. (n.d.). Get poison help. https://poisoncenters.org/get-poison-help
- Environmental Working Group. (n.d.). Glycerin. EWG's Guide to Healthy Cleaning. https://www.ewg.org/cleaners/substances/152313-GLYCERIN/
- Glycerin, 21 C.F.R. § 182.1320. https://www.law.cornell.edu/cfr/text/21/182.1320
- National Center for Biotechnology Information. (n.d.). Glycerol (PubChem compound summary). PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Glycerol
- U.S. Environmental Protection Agency. (n.d.). Safer Chemical Ingredients List. Safer Choice. https://www.epa.gov/saferchoice/safer-ingredients
