What is soap?

What is soap?

Soap is made through a process called saponification. Simply put, lye + fat (lipids) = soap. More techinically, an alkali (lye) is blended with the acids in lipids, resulting in a chemical reaction. 3 mole of alkali meet 1 mole of lipid, creating 3 moles soap and 1 mole glycerol.  A mole is a unit amount in chemistry used to measure large amounts of a small entity, like atoms & molecules.

Many commercial soap companies will remove the glycerol (glycerin), as removal increases shelf life. However, glycerol is a humectant that helps skin lock in moisture and draws moisture from the air, so it’s a great component to leave in soap. The removed glycerol from commercial soaps is often added to other cosmetic products. Hand-crafted soaps typically leave in this naturally occuring result of the soaping process.

How does soap clean? 

One end of a soap molecule is hydrophilic (attracted to water) and the other is hydrophobic (repelled by water). The hydrophobic end binds with oil/dirt/grime, while the hydrophilic attaches to the water and pulls the dirty stuff off of you and down the drain.

What is lye? 

Lye is an aqueous sodium hydroxide (NaOH) solution or an aqueous potassium hydroxide (KOH) solution. Sodium hydroxide results in bar soaps, while potassium hydroxide results in a gel that is easily diluted in water for liquid soaps. Paper Street will occasionally use a 10% NaOH & 90% KOH solution, resulting in a “thicker” liquid soap.

I will cover the safety elements of working with lye in the next blog post.

How do you know how much lye to use to saponify your oils? 

Every oil brings something unique to a soap. Once you’ve chosen your oils and batch size, how do you know how much lye to use? Each oil has its own saponification value. You can find the values and do the calculations manually, but I suggest using a saponification calculation program to check your work. After a few months of soaping, I found it reliable to simply use these calculators and skip doing the math myself. http://soapcalc.net/default.asp is a great option. I recommend reading the Getting Started and Soap Calc Directions before starting. In a future blog post I will use this calculator to create a simple soap recipe, so you can see how I use it.

Another great option is the calculator provided by Hand-crafted Soap & Cosmetic Guild. https://www.soapguild.org/lye-calc.php I find the soapcalc version to be a little more user friendly.