Who would have guessed how entertaining a chemistry lesson on molecular structure could be. We soap makers sometimes think of ourselves as mad scientists. We get a kick out of the chemical reactions that occur during the process of saponification.
Kevin Dunn, PhD is the Elliott Professor of Chemistry at Hampden-Sydney College. He has done and continues to do research projects on the chemistry of handcrafted soap. He is the author of Scientific Soapmaking about the chemistry of cold process soap.
Dunn received a nickname at the session. He became known as Dr. McSoapy.
Hello, Dr. McSoapy!
Dr. McSoapy is an informative and entertaining speaker. For starters, he talked about molecules being like nerds and cheerleaders. As he talked about the attraction of molecules to one another, he brought in the analogy of relationships between high school nerds and cheerleaders.
While causing us to double over in laughter, he taught us about things such as:
- Hydrophilic vs. Lipophilic
- Saturated vs. Unsaturated
- Triacylglycerides, Diacylglycerides and Monoacylglycerides.
My spell check doesn’t like those last three words! Seriously, I’m not kidding. He had us laughing throughout the session. Were you there? Did you laugh?
I took lots of notes. These are just from the first few minutes.
Here’s a little of what we learned:
- A Triacylglyceride is 3 acyl molecules (pronounced with a long a) and 1 glycerin molecule. Just for the record, an acyl is a straight line of neutral molecules. The shorthand for Triacylglyceride is TAG because, as Dr. McSoapy pointed out, AAAG sounds like something is stuck in your throat.
- A Diacylglceride is 2 made up of 2 acyls and 1 glycerin. It’s called a DAG.
- A Monoacylglyceride is 1 acyl and 1 glycerin. Guess what it’s called? No peeking at the answer yet. Did you get it? Right! A MAG.
Dr. McSoapy showed us all kinds of colorful diagrams. A molecule here, a molecule there. Put them together and get something different. There’s a name for that. Stoichiometric — stoichiometric is how much of this will go with how much of that. How’s that for technical jargon? To me it’s how things go together to make a balanced equation. Mostly. He made it so easy to understand. But I’m struggling with passing along that knowledge. So you probably ought to read his book instead of relying on my secondhand rendition.
So let me tell you about some of the things I took away from the session. Things that make more sense to me than acyls and glycerin. We did an experiment. He had bottles of soapy water ready for us. He also had pipettes with either ammonia or vinegar. He had us shake the bottle to get the bubbles going.
See all those bubbles?
Then we added a few drops of vinegar. Guess what? The soapy bubbles disappeared. They ALL disappeared. Like magic. But it’s not magic – it’s soapy science.
No more bubbles!
Here’s where it gets really cool. To this bubble-less soapy water, we added a drop of ammonia. We shook the bottle. Voila! The bubbles were back (see picture of bubbles above)! Fun times.
Dr. McSoapy told us about some of his research. One very interesting finding he shared concerns lye heavy soap. You may have read/heard that cold process soap gets milder over time. To test this idea, Dr. McSoapy and his team did an experiment on a lye heavy soap and showed us the results.
A soap started out lye heavy (can you say ouch?) when it was poured. I don’t remember the exact pH, but it had too much lye in it. After 24 hours, the soap was still lye heavy. However, after 11 weeks, the soap had a pH level very close to normal for soap. The pH was at a safe level. He explained that this happens because the CO2 reacts with the leftover lye to eat it up. Well, those may not have been his exact words, but that’s what my brain heard.
Anyway, it was very interesting to me that in a relatively short amount of time, a lye heavy soap would become a safe soap. The conditions in which the soap cured may have an effect on how quickly the soap becomes safe.
If you end up with a lye heavy soap, be sure to check the pH if you plan to use it. If you make soap from scratch, you know the drill. Every soap may not reach a safe level within 11 weeks as the experimental soap did.
The other finding that I will remember most from this session? Lye Discounting (adding less lye than the oils will use) vs. Superfatting (adding an oil after trace). Based on his research, Dr. McSoapy believes the evidence suggests that superfatting and discounting lye create a similar end result. Why does he think this? Because he has this fancy doodad that can separate out and measure what fatty acids are left over in the soap. And he knows (as we can, too, if we do our research) which fixed oils contain which fatty acids and how much. The fatty acids remaining in the soap were not always from the oil added after trace. And the amounts and types of left over fatty acids were very similar between superfatted and lye discounted soaps that had been made from the same recipe.
His thoughts on why this is the case:
- Some oils react with lye more quickly than other oils do.
- Adding an oil after trace doesn’t guarantee that some of that oil will remain unsaponified. (Something of note here is that jojoba is a special case because it is a wax ester rather than an oil.)
Thank you, Dr. McSoapy for the wonderfully informative and entertaining session.