How to Make Cold-Process Lye Soap

This information is dedicated to all those beginners out there who really want to try their hand at cold process lye soap making, but are afraid of that three-letter ingredient, l-y-e.

I'm here to tell you, and I mean this, if I can do this, so can you.  After I poured the very first plastic cup of those scary lye crystals into a pitcher of distilled water -- and realized nothing "bad" was going to happen, I relaxed and scolded myself for being such a coward.

That was a few months and a few batches of soap ago and I have not yet had a mishap (knock on wood.) As long as you follow these simple directions, everything should turn out just fine.

First, you need a recipe and, by trial and error, this is the formula I have settled on to make my soap.  I like it because the finished soap is a bright, milky-white; lathers well; has good conditioning benefits and makes for a nice, hard bar of soap that lasts a long time.

Old-Fashioned Lye Soap Recipe

10 ounces Canola Oil (the kind you cook with)

6 ounces Coconut Oil (76 Degrees)*
20 ounces Vegetable Shortening (Crisco)
4.853 ounces Food Grade Sodium Hydroxide (lye)*
11.88 ounces Distilled Water
Dyes, herbal additives and/or fragrance (optional)

Yield: 52.73 Ounces Soap

*You may follow the links to see where I purchase these ingredients online.

Supplies

Before we begin, you will need to have these items ready:

Safety goggles
Rubber gloves
Disposable drinking cups (plastic or Styrofoam)
2 Large Wooden or Plastic Spoons (not metal)*
Large glass, stoneware or plastic microwave-safe bowl*
2 large microwave-safe measuring cups (at least 4 cups)
2 candy or digital food thermometers*
Glass or plastic pitcher*
Electric mixing wand
Digital scale (preferably with a tare feature)
Soap molds (wooden frame, sewing cabinet drawer, or glass bread loaf pans)
Wax paper or plastic grocery bags
White vinegar and paper towels for lye-water spills

*Please mark these items with the word "lye," using a permanent marker.  Do not use these items for food preparation once they have been used for soap-making.

Lined Soap Mold

Note:  All ingredients are measured in exact weight, not volume -- this is why a digital scale is preferred. 

Line your soap mold with wax paper or plastic grocery bags. (Make sure any printing on the bags is turned inside-out, or the ink might transfer to your soap.) Smooth out any wrinkles and use a large rubber band or tape to secure the lining to the outside of the mold.

Place the pitcher on the scale and turn on. (If the scale has a tare feature, it will weigh the container and adjust for it automatically.) Pour in the distilled water until the scale indicates the proper weight.

Distilled Water

Put on safety goggles and gloves.

Place plastic or Styrofoam cup on scale and measure appropriate weight of lye crystals.

Pour the lye crystals into the pitcher containing the distilled water (never pour water into the lye,) and stir gently until crystals dissolve. Place the candy or digital thermometer in the lye water. Discard the cup.

Weigh the solid and liquid oils. 

Melt the solid oils (shortening and coconut oil) in the microwave until completely melted. Pour all oils into the large bowl (make sure it is large enough to hold all of the ingredients, including the lye water when it is added, and allow for mixing. I use a large, recycled ceramic crock pot liner for this purpose.)

Place the second thermometer into the oil mixture.

Oils are at 120 F.  Too hot.  

When the lye water has reached a temperature of between 100-110 degrees F and your oils have reached a temperature of between 90-110 degrees F, you are ready to pour the lye water into the bowl containing the oils. (If the lye water temperature is too high, you can place the pitcher in a bowl or sink of cold water to cool it. Watch it closely, it will cool pretty quickly.) 

Once the lye water and oils have been combined, use the mixing stick, pulsing in short bursts, to mix. You will see the mixture starting to turn milky and pudding-like, which is called saponification. 

Saponification has occurred when oil and lye water are combined
to form an opaque mixture.

When you can lift the mixing wand (turn it off first!) out of the mixture and it leaves a noticeable drizzle on top that lays there for a few moments, this is called trace. Add any dyes, herbs or fragrance now and mix gently to incorporate. You are now ready to pour the mixture into your mold(s).

Trace

Pour your mixture into the soap mold(s) and rap each mold firmly on your workspace to remove any air bubbles.

Place the soap mold(s) onto a flat surface and cover with a piece of cardboard. 

Wrap the mold(s) in towels to insulate -- you can't insulate too much. I use two large folded bath towels for this purpose.

Cover mold with towels to insulate for 18-24 hours.

In approximately 18-24 hours, your soap will be ready to un-mold and cut. You will be able to tell if it's ready  when it has reached room temperature. 

Cut your soap into the desired size and place on racks to cure for at least four weeks, at which time it will be ready to use.

You can utilize a wide variety of different oils and fats to produce the type of soap that works for you.  I would strongly suggest you use the lye calculator on Brambleberry.com

After your soap has completely cured, you can dress it up with decorative wrapping, ribbons, twine, or  labels. You might even be interested in selling your soap at craft fairs, farmer's markets or online.

 If you should have any questions about this tutorial or soap-making in general, please feel free to do so in the comment section of this post, or email me at Lom8nance [at] gmail [dot] com.