Introduction to Cold Process Soap Making

Have you ever wanted to try making your own soap? Likely it’s much easier than you think.

I’ve been making soap for a few years now, and was selling soaps at the weekly local market, in pre-pandemic times.

For me, soap making is a lot of fun. I enjoy crafting all sorts of botanical concoctions, and making my own soap allows me to infuse the soap my family uses daily with lovely, nourishing ingredients.

Handmade soaps are such a wonderful substitute for conventional ones that contain artificial fragrances and other questionable additives that are less than ideal for our health and the environment.

Fortunately, making your own cold process soap is really quite simple. Below is a basic guide to get you started.

Acquire Essential Equipment

Having all the necessary equipment on hand is the first step to successful soap making. Check out my post Soap Making Essentials for a detailed list of everything you need to get started.

Determine recipe

Next, you’ll need to decide what recipe you will use so you can ensure you have all the necessary ingredients on hand before you get going. You can use a soap calculator to figure out how much of each ingredient you should use or follow a recipe that an experienced soaper has created.

When first starting out, it’s a good idea to follow a recipe so that you can get into the flow of soap making and get a feel for how different ingredients affect your final product. Various oils, liquids, and add-ins alter the soap in different ways, including the hardness of your soap, how well it lathers, if it’s drying or moisturizing to the skin, etc.

The Nerdy Farmwife has some lovely recipes to try on her blog, including:

I like to have my recipe printed or written out so it’s easy to follow as I work and to jot notes on later on to remind myself of changes I’d like to make next time, things that worked well, and so on.

Keeping a “soap journal” can be helpful for beginners to keep track of what works and what doesn’t. Cold process soap takes several weeks to cure, so it’s easy to forget your process by the time you actually get to start trying out the soap you’ve made.

Gather & prepare ingredients

You are almost ready to make soap! Before you start, review your recipe and prepare all of the necessary ingredients so you have them handy once you start.

If you’re using an herbal tea, make it and let it cool completely before mixing it with lye.

If you’re using add-ins, measure them and set them aside.

Set up your work space

Mixing a lye solution produces toxic fumes. Your work work area should be very well-ventilated. Before working with lye for the first time, check out this lye safety guide to review all the proper precautions you’ll need to take when working with it.

It’s handy to have a sink nearby so you can rinse the lye off things as you go, but if you don’t have a sink in your work space, just set everything aside, out of the way, and rinse it all off at the end.

Set out the soap molds you’ll be using nearby, so they are easily accessible when you’re ready for them.

Keep a few rags on hand to wipe up any spills or splashes.

Mix the lye solution

Weigh the liquid (water, tea, milk, etc.) in a heat proof pitcher.

Put on your safety goggles and gloves. You’ll want to keep your protective gear on while working with the lye solution and raw soap batter, as lye is a caustic chemical that can cause damage to your eyes & skin. It is quite toxic and should be kept well out of reach of children and animals.

Using your specified lye cup, measure the lye. Firmly re-cap your lye container before proceeding.

Next, slowly sprinkle the lye into the liquid, while stirring gently. Avoid breathing in the strong fumes that are produced immediately when the lye begins to react with the liquid.

Set the lye solution aside to cool a bit. Be sure to put it somewhere well out of reach of pets and children.

Gently rinse the spoon and lye cup with cold water and set them aside. Remember to keep them separate from utensils used for cooking or serving food! Throughly wipe the area where you were working in case any lye spilled.

Let the lye cool for about 30 minutes. While you wait, begin to prepare the oils & butters.

Mix the oils & butters

Weigh the liquid oils into your soaping pot. Then weigh out all your butters and solid oils and heat them in small saucepan til they are melted. Mix them in with the liquid oils.

Combine lye solution with oils

Check the temperatures of your lye solution and oil/butters mix. They should both be around 90-115 degrees F (32-46 degrees C). Heat the oils & mixture, if necessary, to bring it within 20 degrees of the temperature of the lye solution.

Now you can add the lye solution into your soaping pot. Rinse the container you mixed the lye solution with cold water and set it aside.

Bring to trace

Fully submerge your immersion blender into the soap pot and tilt it slightly (this helps prevent splattering).

Turn the blender on and gently stir for 30 seconds or so. Then turn it off and continue stirring for 30 seconds or so. Continue stirring, alternating with the blender on and off until the batter begins to thicken slightly. This could happen quickly or take up to 10 minutes or so.

Check for trace by lifting the blender out of the soap batter and drizzling it over itself. If the batter leaves a pattern before sinking back into itself, stop stirring. Let the soap batter sit for a minute and then use the method described above to check for trace again. This process looks for a “false trace” — when the soap batter thins out again after appearing to have traced. If the batter still “traces,” you can move on to the next step. Otherwise, stir more until trace is reached.

Add in extra ingredients

Once your soap batter has traced, you’ll stir in the extra ingredients you prepared earlier & any essential oils, if you’re using them. Keep in mind that some extras like clay, honey, or certain fragrances can cause the soap batter to thicken very quickly, making it difficult to pour, so you’ll want to work fast after this step.

Pour soap batter into mold

Pour the batter into the molds you prepared earlier. Smooth the tops of your soaps with a spoon or spatula. Place the spoon/spatula back into your soaping pot and set it aside. Cover your soap with plastic or wax paper to help prevent soda ash.

You can now cover the mold with a towel or blanket to keep the heat in or place the mold in the refrigerator to keep the soap from overheating & cracking as it sets. Honestly, I never do either. I just pour my soap into molds, cover it (and sometimes I don’t even bother covering it) then leave it on the counter til the next day or so. This has always worked for me. Of course there are good reasons behind monitoring the temperature of your soap while it sets, but I’m not going to go into all of that here.

Clean up work space

Throughly wipe up your work space to clean up any spills. I put all soap covered pots, containers, and utensils aside and let them sit overnight and then soak, rinse, and put everything away the following day.

Let soap set

Leave the soap to set in the mold 24-48 hours. If it’s too soft to remove from the mold, let it set for another day or so.

Remove soap from molds

Gently remove the hardened soap from the molds. If you made soap loaves, you can cut them into bars immediately or let the loaf firm up for a few more days and then slice it.

Let soap cure

Set soap on a plastic or coated metal rack (or on sheets of wax paper) to cure for 4-6 weeks minimum before using. Softer soaps may take several more weeks to fully cure. While it can be hard to wait for your soaps to fully harden before using, it is worth it, as properly cured soaps will last much longer.

You can tell your soap is cured and ready to use when it’s nice and firm. Check for firmness by gently pressing your finger into the bar, if the bar gives, let it cure longer. If it’s nice & hard and it’s been at least 4-6 weeks, it’s ready to go.

Soaps with a higher amount of butters and hard oils will harden faster. Soaps with a high percentage of soft oils may take a very long time to fully cure.

So, there you have a basic introduction to cold process soap making. In truth, there is so much more to discuss when it comes to soaping. My soaps are unscented and simple, including only natural ingredients. I’ve invested in a few cute silicon molds that make my bars look nice and I don’t get much fancier than that. It can be that simple. On the other hand, you can add different colorants & fragrances and use a variety of different techniques to make soaps that are truly a work of art. Make it as simple or intricate as you want. And most importantly, have fun with it.

If you should run into issues with a batch (or two!) of soap, check out the Nerdy Farmwife’s excellent troubleshooting guide.

Happy Soap Making!