Updated: Apr 15, 2022
Soap making isn't rocket science, but it is chemistry. You have to understand the interactions between ingredients. You have to know how much oil to formulate or how certain natural ingredients will change colour in that solution. Each soap begins with a very very specific formula that is carefully calculated to include sodium hydroxide. If the formula requires .032oz of a certain oil, that doesn't mean .05 or .02 - it has to be exact.
Speaking of sodium hydroxide (lye), it is impossible to make soap without it. All true bars of soap are made with sodium hydroxide (potassium hydroxide is used for liquid soap). If your bar doesn't have this ingredient, then it's basically detergent. How can you tell? Look for any oils like sodium cocoate, sodium olivate or the word saponification. This means the oils have been mixed with lye to create the soap.
The cold process way of making soap involves using very cold distilled water in exact amounts and carefully adding the sodium hydroxide to that cold distilled water in exact amounts. NEVER the other way around. If you were to add water to sodium hydroxide.....kaboom.
Sodium hydroxide is caustic. It doesn't play well with metals like aluminum (it creates hydrogen gas) and it's dangerous to breathe the fumes. It can burn your skin and kill you if accidentally swallowed (not that I'm tasting lye! but kiddos and pets should never be around) When I make my lye solutions, I wear a mask, protective eye gear, gloves, long sleeves, pants, shoes and make sure the ventilation is on. You might say, I need my own PPE. You'll notice a more serious looking mask in the picture below. I sometimes use this one if I'm making many batches in one day, otherwise a basic mask is fine.
Once the lye is stirred gently, an exothermic reaction occurs and the cold water instantly becomes very hot. It changes from a cloudy to clear solution and also becomes cooler after 15-30 minutes or so. Once it reaches a certain temperature, it can be carefully mixed with the oil solution mixture, and then colours and scents are added.
Some of the PPE used when working with lye
As the lye water is mixed with the mixture of oils, this is when saponification begins. Without getting too technical, saponification is the chemical reaction between the lye water and the fatty acids of the oils. This process usually takes 24-48 hours and during that time, it's best not to manipulate the loaf of soap with bare hands. After that time, it is safe as the loaf hardens and is cut into slices. The slices are then left on a custom shelf (with proper temp and humidity) to cure and the sodium hydroxide is transformed. The curing process takes about 4-6 weeks during which time the ingredients settle and the bar becomes closer to an 8-9 ph level for us to use. At that point the lye is no more - it is soap. Magic :)
Actually the real magic is developing the right combination of scents and colours to make designs. While this step isn't dangerous, it is tricky and if a mistake is made, the loaf is lost. Rebatching the soap isn't ideal and usually fails, so the only thing to do is use it 'ugly' or cut it up and incorporate it into another batch somehow. Ingredients can be expensive, so mistakes are carefully avoided! Sometimes colours don't behave well and turn into completely different shades. Sometimes, scents make the soap batter seize quickly so it's difficult to pour into molds. But when the stars align and all goes well, the slices are pretty and smell wonderful.
And so while soap making is chemistry, it's also design and creativity. I guess my background in interior design and art helps me in some way to create different designs for soap. There are endless possibilities. More importantly, the knowledge of exactly what goes into these bars of soap is gratifying. This is one of the reasons that prompted me to start the second business....wanting the best ingredients possible. So the next time you pick up a bar of soap, you'll know the process it took to make it, but also read the label for the ingredients list and make sure you're getting soap and not detergent.