What the Heck is Soap?

So, you've seen a few of my soaps here and you've probably seen folks selling soap at craft shows or farmer's markets. Did you ever wonder just how exactly one makes soap from scratch at home? What does one need in order to make soap? And just what the heck is soap anyway?

In a nutshell, soap is made when oils are combined with sodium hydroxide (lye). That's really about it.

Let's expand a bit on that, though. Here's where I lay some chemistry on you. I promise it won't hurt much. To make soap, a chemical reaction has to take place between an acid (the fats and oils in a soap recipe) and a base (a lye solution of sodium hydroxide and water). This chemical reaction, which is called saponification, produces soap and glycerin, a natural by-product of soapmaking.

The chemical structure of a typical soap

The mention of lye can make some people uncomfortable, conjuring images of harsh soaps and irritated skin. The truth is, you cannot make soap without lye. It's just not possible. The good news is that when soap is properly made, there is no lye present in the final product. Great-grandma may have made some lye-heavy batches in her day, and too much lye can certainly make for an unpleasant bar. But soapmaking has come a long way in the past couple of decades and today's soapmakers use things like gram scales and lye calculators to make sure that they are using exactly the right amount of lye to oils.

See, each molecule of sodium hydroxide combines with a molecule of oil. During saponification, triglycerides in the oils break down into fatty acids and glycerols. The fatty acids react with the sodium ions, creating sodium compounds that are better known as soap. (So soap is chemically a salt. Cool, huh?) And where does all of that skin-loving glycerin that I mentioned earlier come from? The newly liberated glycerols react with the hydroxide ions to create glycerin.

Of course, you can't just dump some sodium hydroxide into some oils and get soap. There is a process.

Dig my look?

What does that process look like? First and foremost is safety. Lye is caustic and it must be handled with respect. A speck of lye in your eye will really ruin your day.

Here are the basic safety rules: Suit up with goggles, gloves, long sleeves, long pants, and close-toed shoes. Take care to not breathe the lye fumes. Standing back and running the exhaust fan is usually enough, but wear a painter's or dust mask if you want to. If you get lye or raw soap on yourself, rinse thoroughly with water and then rinse with vinegar. (I always have a spritzer of vinegar handy.) Protect your countertops and appliances, too. I take a tip from Dexter and cover everything with plastic drop cloths. I also lay down paper bags so I have a place to rest my soapy utensils.

A few words about equipment: I use either heavy-duty plastic (polypropylene is my plastic of choice - the kind with the recycling code with the "5" and "PP" on the bottom) or stainless steel for making soap. Never use aluminum, tin, copper, teflon, or any other metals, as they will react badly with lye. I also do not use glass - over time, lye can etch tiny cracks into the glass and one day it may decide to just shatter.

Kitchen prepped for soapmaking

Every soapmaker's process varies, but here's how I do things. I am a mise en place kind of soaper and I like everything out and measured before I get started. First I measure out my oils and butters for my batch size, which is usually two pounds of oils. (I measure everything in grams for greater accuracy.) My basic recipe typically includes olive oil, coconut oil, palm oil (from a sustainable source), shea butter, and/or avocado oil. I like to measure out my oils in separate bowls so I can put some back if I over-measure. Plus, I'm OCD and feel reassured to see four bowls of oils if I'm using four oils in my soap. I gently heat the oils in the microwave to melt them and to get them a bit warmer. When all of my oils are warm and melted, I combine them into one big bowl.

I also like to measure out my fragrance or essential oils and get any colorants ready. I usually use powdered oxides and micas and mix them with a bit of liquid glycerin to work out any clumps.

Next, I get my lye solution ready. As discussed, soap is made through a chemical reaction with oils and sodium hydroxide. You need some sort of liquid, though, to dissolve the sodium hydroxide and to act as a carrier, ensuring that all of the lye gets to the oils. Water (preferably distilled water) is usually used, but beer, wine, fruit juices, milks (goat's milk being a particular favorite), etc. can also be used in place of the water. I keep my liquids in the fridge so that the lye solution doesn't get too hot. To make the lye solution, I measure out my lye flakes into a cup, and then slowly sprinkle my lye flakes into my cold liquid, stirring as I go. NEVER ADD WATER TO LYE - ALWAYS ADD LYE TO WATER. The lye solution usually heats up to about 165 degrees F when I start with cold liquids, and I like the temperature to be more like 100-110 degrees before I combine it with the oils. So, I always make sure I have an ice bath waiting in the sink so I can rest my lye container in the frigid water, thus cooling it down faster. After about 10-15 minutes of stirring my lye solution in the ice bath, it's cool enough to add to my oils.

Adding lye flakes to water (inside a dishpan in case of any spills); stirring lye solution in ice bath

Some soapmakers wait until "trace" (something I'll explain in a moment) before adding fragrance or essential oils, but I usually go ahead and add my fragrance to the oils once they've cooled down to about 110 degrees or so. I do this for a couple of reasons. First, this way I won't forget to add it. Second, if my fragrance is finicky, the oils will give me a bit of a buffer against seizing, ricing, or acceleration.

Adding lye solution to oils; emulsifying lye and oils with stick blender

When both my oils and my lye solution are somewhere around 100-110 degrees, I slowly add the lye solution to the oils, stirring as I go. To help speed things along, I use a stick blender to mix and emulsify the soap batter.

Look closely. See the trails of soap on the surface? That's trace.

How do you know when to pour?

Soapmakers look for something called "trace." Trace occurs when the soap batter is completely emulsified and will not separate into a watery, oily mess. How do you test for trace? Dip a spoon or spatula into the soap and dribble a bit on top. If the dribbles leave a trail of soap that stays on the surface for a couple of moments before sinking back into the batter, that's trace. Trace can be light or heavy, depending on how long you mix it and what consistency you want. Lighter trace is good for swirling, heavier trace is good for layering.

Once I've reach my desired level of trace, I pour my soap into my mold. Some molds (like silicone, plastic or acrylic) don't need to be lined, but others (like wooden molds) do. To line a mold, I use freezer paper with the shiny side facing in.

Freshly poured soap in the mold

Once the soap is in the mold, I pop a lid on it and insulate it with a couple of towels. I like for my soaps to go through gel phase, which is a part of the saponification process in which the soap heats up and becomes rather gelatinous. After 24 hours, gel phase is complete and the soap can be cut. Soap doesn't have to go through gel phase to become soap. Some soapers purposely avoid gelling by popping the soap into the fridge or freezer because they like the color or texture of ungelled soaps better. Ungelled soap still saponifies, it just takes a few days longer.

After about 4-6 weeks of curing time, the soaps are ready to use!

And that's pretty much it! Now you know the basics of soapmaking. I hope it was interesting!

Until next time ...