Go here for a revised, updated and expanded tutorial on how to make cold process soap from scratch.

DIY Cold Process Soapmaking

Soapmaking can be a lot of fun and very rewarding. However, it’s not something to just jump right into without first some research and understanding of the process. Not only are there precautions that need to be taken when making cold process soaps, but a failed batch can be a very expensive lesson.

Because of the many dangers associated with soapmaking due to the use of lye – also known as sodium hydroxide – and the plethora of information to be had, I recommend that you carefully research the process before starting out on your own. Details on where to obtain additional information will be included within this article.

Soapmaking involves a chemical process in which sodium hydroxide (lye) reacts with oils to make soap. This process is called saponification. Because this process requires the use of lye, important safety precautions must be taken. Rubber gloves and safety glasses should be worn during the soapmaking process, and vinegar, which neutralizes the lye, should be kept on hand in case of an accidental spill for clean up. However, water and not vinegar should be used to flush lye from skin if contact occurs. In addition to the necessary safety equipment needed for your journey into making cold process soap, there is other required equipment you’ll need to get started.

First and foremost you will need to acquire lye. Because without lye, there is no soap. The main components to make a true bar of soap are fat(s) – such as oils and butters – and an alkali – more commonly known as lye. You should be able to find lye in the plumbing section of your hardware store, at a local chemical supply store, or online. For those just getting started and without the need for a 50lb. bag of lye available from chemical supply stores, you can buy Roebic Heavy Duty Crystal Drain Opener in 2lb. containers at Lowe’s stores. (It contains 100% sodium hydroxide also known as caustic soda.) Alternatively, Red Devil Lye can be purchased online. The brand doesn’t really matter, but it must be 99% or more pure sodium hydroxide. (If you are local to Roanoke, VA you can purchase 50lb. bags of sodium hydroxide beads locally in 50lb. bags from ChemSolv. Just be sure to transfer your bag of lye to a plastic container or double garbage bag lined box that you can seal after opening.)

In addition to the lye, you’ll also need a large pot for mixing the soap. I recommend a large stainless steel pot. What type of pot you use is up to you, however, your pot cannot be aluminum. Lye reacts badly with aluminum so remember to never mix the two. You’ll also need an accurate scale to weigh your ingredients in either ounces or grams. You can use digital postal scale from an office supply store. Just be sure the scale is calibrated properly and can handle the amount of weight you will be using. You’ll also need a thermometer or two to measure the temps of your oils and lye solution. And, you’ll find that a stick blender– also known as an immersion blender – is your best friend in making soap. You can hand stir, but this method can take you hours over minutes and a stick blender also ensures even distribution of ingredients. And then of course there are the molds, soapmaking oils, and distilled water to be mixed with the lye.

There are several types of molds you can use to create cold process soap. You can purchase tray molds that are basically hard plastic molds that will create numerous bars of soap at once. These molds should be marked suitable for cold process soapmaking since the soap gets very hot during the saponification process. You can also easily build a mold from wood, with a bottom and four sides. This type of mold will produce a log of soap that you would then cut into slices. When using a wooden mold, you must line it with parchment paper to aid in easy removal of the soap. (Freezer paper is not a good idea as it melts to the soap and mold.) Lining your mold is sort of like wrapping a present except that you are wrapping the inside of the box rather than the outside. It takes some practice to get it right. The parchment should then be secured with tape to the mold. Alternatively, you can line your mold with plastic film or a plastic office sized garbage bag. Just be sure to tape the material to the top of the mold for easy removal. You can learn how to make your own wooden soap molds here. (You can also make silicone soap molds.)

Next, we’re on to oils. The soapmaking oils are an important part of your soap. The types of oils you use will determine the properties that your soap will have. For example, three of the most popular soapmaking oils, especially for beginners, are olive oil, coconut oil, and palm oil. The olive oil helps create a moisturizing bar with a stable lather; coconut oil produces a hard, cleansing bar with a fluffy lather; and palm oil makes for a hard bar with a stable lather. Each of these oils has its own SAP (or saponification) value which determines how much lye should be used in the soap recipe for saponification to occur in such a way that it makes soap. Too much lye and you have an unusable bar of soap. Not enough and you could end up with a really soft soap with excess oil. A great source for learning more about the saponification process and the properties of various soapmaking fats & oils is Susan Miller Cavitch’s book The Soapmaker’s Companion. Her book also contains a great troubleshooting section and several of her own recipes. When creating your own recipes for soap, there are also a lot of additional free resources to help you with this process. Lye calculators, for example, will automatically calculate the amount of lye you need in a recipe based on the amounts and types of oils you plan to incorporate into your recipe. You can find multiple links to lye calculators by conducting a google search. Although I like to use the lye calculator at Majestic Mountain Sage. It is good practice to always double check the amount of lye in a recipe with a lye calculator if you are unsure of its source.

Let’s get down to business!

So, I guess by now you’re wondering just what you do with all of that lye and oil and equipment. Well, I’ll tell you. You make soap! Your best bet is to start by preparing your mold so that it is ready when your soap is ready to be poured. You’ll also need to cut out cardboard that will fit over the top of your mold. The cardboard will be used to help insulate your soap after it is made. Once these steps are complete, you would then measure out your distilled water as called for in the recipe you are using.

Measure the amount of distilled water called for in your recipe out in fluid ounces.

Pour your distilled water into a non aluminum container. (I like to use plastic pitchers.)

Next, measure out your lye. Be sure you have on all of your safety gear for this. Lye gets VERY hot, and chemical burns are never any fun. Be sure to have vinegar open and close by for any spills. For the lye, you will be weighing the amount needed with your scale. Place the container you’re using to measure the lye onto the scale, press tare to zero it out, then slowly pour the lye onto the scale until you reach the amount needed.

Then slowly pour your lye into the water, never the other way around as it could result in a not so pleasant volcano effect. Stir your lye into the water with a plastic or wooden spoon until it dissolves. Now set it aside to cool. If you’re mixing the lye inside, keep it on the stove with the exhaust fan turned on and step away. Or allow it to cool outside to avoid the nasty fumes. Be sure there are no children or animals underfoot who could get hurt.

Next we’re on to the oils! While the lye is cooling, you can weigh and melt your oils. I normally melt my oils all together in a large pot on the stove at medium heat. You can also melt the oils separately in canning jars within a water bath. First, however, you must weigh your oils on the scale. Weigh each oil individually. Set your container on the scale, hit tare so it zeros the weight, then slowly add the oils to the container until you’ve reached the weight the recipe calls for.

Repeat this process for all oils and fats in your recipe. I usually start with the solids first so I am adding the liquids to the pot last. Stir the oils until they are completely melted, then remove from heat.

Once your lye has cooled to at least 120 degrees F, though I find I like to use my lye-water solution between 95 and 100 degrees F, you can generally begin pouring the lye-water into your oils. The temperature of the oils can vary depending on what the recipe you are using calls for, but the oils should not be hotter than the lye. If you aren’t sure how a recipe will react at higher temps, then mix at between 95-100 degrees F. (Refer to The Soapmaker’s Companion for information on why temperatures matter.) With your handy stick blender ready to go, very slowly pour the lye-water into the oils.

Begin stirring with the stick blender on low. As the lye and oil begins to incorporate, you can switch the blender to high. Stir well, moving the blender all over the bottom of the pot and up through the soap mixture.

You will continue to stir until you reach what is known as trace. When the soap has reached trace, it will sort of look like cream of wheat or a custard. When you pull the blender through the soap, it should leave a line following it, and if you pull some of the soap up then drop it on the surface of the soap, the soap should be able to support that drop. Should you not reach trace, within 15 minutes, you can rest for about 15 minutes, then start mixing again. Some oils used in soapmaking are slower to trace. Olive oil, for example, can take a much longer time to trace than other oils unless it is mixed with other oils whose properties promote a quick trace.

You would stir in any additives you’d like to use in your soap, such as fragrance or collodial oatmeal, once your soap has reached a light trace where it is just barely leaving a trail or supporting a drop. Mix these in well, especially any essential or fragrance oils, so you won’t have any “hot spots” in your soap. Generally fragrance oils account for 3-6% of your soap, but be sure to follow manufacturer’s recommendations if they are available. Note that some fragrances and essential oils can accelerate trace. Once your additives have been thoroughly incorporated, you’re ready to pour your soap into its mold!

Slowly pour your soap into the prepared mold. Drop the mold with the soap onto the counter several times to help remove any air bubbles.