Making your own soap is not, I admit, a do-or-die survival skill, but it certainly is a great self-reliance booster. And just think of the benefits to morale, knowing you won’t have to smell a lot of BO after the power grid goes down and the grocery store runs out of soap. Plus, it’s so easy!
This is the first of two articles on making soap. In this first article, we’ll see how to mix the ingredients. In the second, we’ll see how to form the soap and cure it.
Ingredients:
- 1 kg (1000 g) lard
- 200 g coconut oil
- 60 g olive oil
- 175 g lye (sodium hydroxide, NaOH)
- 350 mL water
- 1 Tspn essential oil of lemon (optional)
Equipment:
- Stainless steel or enameled cast iron pot
- Mixing bowls
- Thermometer
- Steel or plastic spatula
- Ice
- Mixer (optional)
Safety:
- Use goggles and gloves
- Prepare in a well-ventilated area because of fumes generated by the lye
- Never add water to lye; always add lye to water
- Have a plentiful water supply ready in case the lye contacts your skin or eyes
- Always test the soap on your hands before using on more sensitive parts to make sure it isn’t too harsh.
Preparation:
See part 2 for preparation instructions. For now, go ahead and gather the ingredients, and you can mix this up next week. This part is very important, though; you need to be sure you calculate the right amount of lye based on the fat you have. Be sure you study and understand the following section.
This batch of my homemade soap won a blue ribbon at the county fair.
What is Saponification Value?
The saponification value of a fat is a number indicating how much lye you need to fully react with the fat you have. However, don’t use the full amount of lye indicated by your calculation, because you don’t want all the fat to react; you want all the lye to react. Therefore, however much lye you come up with based on your calculation, subtract 5 %. This ensures that the lye will be the limiting reagent in the reaction, so you have a small amount of fat left over. If there were lye left over, it would be in your soap, and would react with the fats in your skin, drying it out and irritating it. Not good, especially in those more sensitive parts. Leaving a small amount of fat, instead of lye, makes the soap gentle enough for frequent use.
The following is a bit complicated, but I’ll clarify everything with an example.
The saponification value is an index value, not a unit value, so the number you want to use in your calculation is the one under the type of lye you’re using (the derived value), not the actual SAP value in the second column in the table below. If you’re using sodium hydroxide lye, use the number under NAOH. If you’re using potassium hydroxide lye, use the number under KOH.
The SAP value is defined for use with potassium hydroxide and is expressed in milligrams of potassium hydroxide per gram of fat. It will work for any unit of weight, as long as you use the same unit for the fat and the lye (grams and grams, or ounces and ounces, etc). The value for NaOH is calculated by multiplying the SAP value for KOH by 0.713, which is the ratio of the molecular weights of NaOH and KOH.
The values expressed in the NaOH and KOH columns are derived values; the derived value is the number of grams (not milligrams) per gram of lye, using the average SAP value in the SAP column. SAP values vary based on conditions under which the fat or oil was prepared. Using the average has always worked for me, but always test the soap on your hands before using on more sensitive parts to be sure your soap isn’t too harsh.
Example of Calculating Saponification Value for Various Fats:
If you have 1000 g of lard, 200 g coconut oil, and 60 g olive oil in your batch and you’re using NaOH (sodium hydroxide) lye, multiply the weight of your fats by the relevant value and add them up:
Lard — 1000 x 0.138 = 138 g of NaOH lye
Coconut oil — 200 x 0.178 = 35.6 g lye
Olive oil — 60 x 0.133 = 7.98 g lye
Add them up to get a to get the total amount of lye: 182 g
Then subtract 5% to make the lye the limiting reagent:
182 x 0.95 = 173 g of NaOH lye
I rounded up to 175 g for ease of measuring, and it turned out fine.
Saponification Table (Reproduced from From Nature With Love).
|
 |
Mixing Water and Lye
NOTE: Handling lye is dangerous. You need goggles; contact with eyes can cause immediate blinding injury. While I didn’t wear gloves in the video, you can get burns on your hands if you don’t. Have a plentiful supply of water handy for rinsing in case of contact with skin or eyes. Also, rinse all your stuff with lots of water outside or down the drain to dispose of the lye. It will be fine to use again for cooking, but only after all the lye is washed away.
You need twice as much water, by weight, as lye. So if you have 175 g of lye, you need 350 g of water, which is 350 mL of water.
Never add water to lye; it can cause a violent reaction as the water heats rapidly to the boiling point and vaporizes explosively, spattering you with lye. Instead, add the lye to the water.
Mix gently with the spatula, if necessary, though the lye should all dissolve readily without mixing. Do not use a mechanical mixer — you risk more spattering.
Place the mixture in an ice bath to cool it back down to about 100 F before mixing with the fat, because otherwise it will set up too quickly and you won’t have a chance to pour it into your mold. But we’ll touch on that again in part two.
Until then, get your ingredients ordered, and next week we’ll see part 2!
~SnoMan
What is a good source for lye?
I always used Frank from the grocery store. Worked greAt.
By-products of this reaction are soap and glycerine. Is it not necessary to separate glycerine? Or is it fine?