Until recently, I’ve never wondered how soap is made. It’s one of those little things in life we take for granted, and it has never, ever crossed my mind to find out. Same goes for toothpaste and shampoos, and waste water management for that matter.
When I was in my bath bomb making craze, I came across blogs describing “how to make soaps”.
Those blogs and youtube tutorials seemed simple enough. You add X amount of fat, dump Y amount of lye without blowing yourself or your house up. Blend like crazy to form “trace” and then pour that into a mold. Wait Z weeks for it to “cure”, and voila – You Just Made Soap!
The skeptical engineer in me couldn’t believe things are so simple. This, by the way, is another occupational hazard of being an engineer. When there are two paths, one straight, and one winding towards god knows where, we will, inevitably, choose the longest, weirdest path. Why? I wish I know why…
Anyway, I started reading up on the process of saponification
At first glance, it seems really simple: Fat + Base = Glycerol + Soap!
But the more I read into each nitty gritty chemical detail, the more I realized that to create the perfect bar of soap, it will take a lot more reading up, batches and batches of experiments, lots of engineering and testing, and a couple cases of wine to see us through. Brooke likes white, I love red… We should probably order a mixed case instead of buying it bottle by bottle… I wonder if we can add the cost of wine to our expenses. Maybe we can add that under our research into making Merlot or Chardonnay soap. Heehee, all these anti-oxidants, you got to wonder if it works on skin.
Anyway… back to my original topic…
Any fat/oil comprises of one to three fatty acid(s) bonded to a single glycerol molecule.
Depending on how many fatty acids are bonded to the glycerol molecule, it forms different types of glyceride.
- If one fatty acid bonds to one glycerol molecule, it is known as monoglyceride.
- If there are two fatty acids bonded to one glycerol molecule, it is called diglyceride.
- If Mr. Glycerol is extremely popular, and three fatty acids bonded with it, this is then known as a triglyceride.
For nerds like us, who need to see it in complicated chemical diagrams to tell ourselves it is legit information – here are some examples of mono, di, triglycerides.
The entire saponification process can be described simply as the introduction of this new, even more popular guy at the school playground – NaOH, nickname – Lye. During the introduction process, all the fatty acid(s) decides that Na is way cooler than glycerol, and they decided to break their friendship with glycerol, and form a new friendship with Na. Thank god for this super popular Lye guy, this newfound friendship results in soap. And now the once popular glycerol molecule gets left behind.
An example of saponification process:
The process is really pretty straightforward. But what made it technically challenging is the fact that each oil/fat comprises of different types of fatty acids in varying percentage. Depending on what type of fatty acids are present, the resulting soap (which is essentially a salt), will have completely different soaping properties. Also, as Brooke pointed out, instead of introducing Mr NaOH, if we introduce another just as cool character, KOH, we would get a much softer soap product, and that is essentially what most liquid soaps are made from.
Brooke, Puja and I trawled through internet and textbooks to gather information and here’s a summary of different soap properties by different types of fatty acid.
Based on the table below, and our highly developed sense of trend detection honed by our day job of detecting defects for a semiconductor wafer, we quickly conclude that what has great lathering properties seems to be lacking in moisturizing ability. A blend of acids is definitely needed to reach a balance.
Also, monoglyceride and diglycerides are not as stable as triglycerides, so they tend to turn rancid easily, but none of the literature touched on that in detail. So for the rancidity column, there are a lot of “To be determined” cells we have to fill up.
To figure out which oils/fats/blends to use, we’ve also compiled a list of typical oils/fats used in soap-making and their estimated fatty acid composition.
Come this Sunday, we’ll all be in Puja’s house, pouring over each dataset, design experimental splits and make our first raw material purchase as a team. Next week, we start making our first test bars and then we’ll characterize those after they are done curing.
It’s not going to be easy, but I’ll say this for the group – no matter what curveballs soapmaking throws at us, we’ll still go in with our heads held high, waiting for it to smack us in the head. Oh, by the way, that’s another justification for why we need to get that case of wine.
And if you like our gung-ho spirit, please leave us an encouraging comment. We’ll really appreciate it 🙂