The Process
First Things First
Using your scale, measure out your fats and/or oils in a lye resistant and heat proof container. A glass or stainless steel pot will work fine. Make sure you do not use aluminum.
Heat the oils until melted. Once the oils have melted, remove the pot from the heat source. You can check the temperature of the oils using your thermometer. (More on temperatures in the Mixing section below)
Be Safe
Put on your protective gear: eye protection, long sleeves, long pants, shoes, and gloves.
Mixing The Lye Water
It’s a good idea to mix your lye water in a stable, well ventilated area. Mixing lye in the water causes a endothermic reaction, the water heats up instantly and fumes will rise from the solution. Do not intentionally breathe the fumes, they are caustic.
Using a heat proof container, measure out the amount of water called for in your recipe. Cold water should be used. Do not use hot water. Water is about the only thing that weighs the same as it measures. So, you can either use a measure cup or your scale to measure the water.
Using your scale and a lye proof container carefully measure out the amount of lye needed for your recipe. You will want to have your water ready before measuring the lye so you can add your lye to the water as soon as possible. Lye is hygroscopic and will leach moisture from the air. You don’t want to leave your measured lye sitting out.
Carefully add the lye to the cold water. Do not add water to lye, it will cause a violent reaction and you could end up with caustic solution all over you and the area you are in. Once you have added the lye to the water, you will need to stir. If you wait too long to stir, the lye will form a clump in the bottom of your lye water mixing container and it is very hard to get this lump to dissolve once it has formed. If you let a lump form, you will be stirring for a while to get it to dissolve.
Add Lye Water to Oils
Check the temperature of your melted fats/oils and also the temperature of your lye solution. You will want the temperature of both of these mixtures to be about the same and somewhere in the region of from 95°F to 115°F. You may have to wait a bit for these temperatures to be similar.
The oils will retain heat longer than the lye water. That is why we heated them up first. If the temperatures are off slightly it’s not a cause for alarm. Smaller batches can withstand higher temperatures than larger batches.
If you’re nervous about adding the lye water to the oils, you might want to move the container holding the oils to the sink. That way, if there are any spills they will be contained.
Slowly pour the lye solution into the fats/oils with one hand and begin stirring the mixture with your other hand. You will be stirring the soap for a while, and possibly a couple hours depending on the recipe. If you have to stop stirring for a while, it’s okay. You do not have to stir constantly, you can take a break. Stir the soap constantly for the first 10 or15 minutes or until the soap mixture appears to start saying mixed. Then yu can stir the soap every 10 or so minutes to incorporate everything back together until you get to trace.
Trace. What is it?
You’ve been stirring the soap for quite some time. When you first started stirring the mixture was thin and watery looking. As the lye, water and fats/oils begin reacting, the mixture will slowly thicken and turn opaque.
Trace is a term in soap making used to describe the consistency of soap when it’s about ready to pour into the mold. The soap mixture will have the consistency of thin pudding or gravy. When you drizzle some of the soap mixture off your spoon while slightly dragging the spoon across the pot, and drizzled line of soap forms a line that appears to sit on top of the mixture for a few seconds, this is trace.
Scent and Color
Once the soap has started to trace, it’s time to add goodies to your soap. Now is the time to add fragrance, essential oils, and color. After you add these items to your soap you will want to stir for a few more minutes to make sure these items are distributed thought your soap batch.
Into the Mold
If you’re nervous about this part and your soap batch and mold are small enough, you can place your mold in the sink. Otherwise, you might want to put several layers of newspaper under you mold and have some paper towels ready just in case. Carefully pour the soap in your lined mold and use a bowl scrapper spatula to get all the soap out of your mixing container and into the mold.
Mold Time
Depending on the environment you live in and how hot or cold your weather is, you might want to insulate your soap mold. Place a small garbage back over the soap and then place an old blanket or some other type of covering around your soap. Sometimes we just place couple folded cardboard on top of the mold for insulation. It will take approximately 24 hours for you soap to completely set up to where it can be removed from the mold and cut.
After your soap is safe and sound in it’s mold, you can take off your safety gear and put your feet up. Now we wait. It’s a good idea to make notes about the batch of soap you just made so that if you really like it, you can duplicate it later, otherwise you may forget exactly what you did.
If you peek at your soap (and we know you will) a few hours after you have poured it into the mold, especially if you have insulated it, you may see what is called the gel stage. The soap in the center of your mold will appear to be clear and the mold will be very warm and may even be hot.
Unmolding Your New Soap
You will want to wear your gloves when handling fresh shop. You soap may still be quite caustic when it’s time to remove it from the mold and cut it.
If you used a plastic unlined mold, place your gloved hand on top of the soap and turn the mold open end down. Gently press on the back of the mold to get the soap to release. If the soap does not want to come out of the mold, it may need more mold time, or it may need to be placed in the freezer to pursued it to let go. Freezing will cause the soap to contract and become firmer which makes it easier to remove from the mold. If it still won’t come out, you might want to wait a little bit after freezing and let the soap sweat. Sweaty soap is slippery and should come out of the mold more easily.
If you lined the mold you used, then you can remove or cut the tape you used to hold up the liner and use the same procedure above and flip the mold over to get the soap to come out. Then you can peel the liner off the soap.
Once the soap is out of the mold, you can cut the soap into bars. Stacking the bars so that there will be some air circulation around each bar to aid in the curing process.
Cure Time
It will be some time before your cold processed soap is ready to use. Cure time is usually from 3 to 6 weeks. During this time the soap will lose moisture, become harder and will also decrease in pH. The longer you wait, the milder and harder the bars will be. I have a couple of bars that are 10 years old and one bar of soap that is almost twenty.