Jane’s Castile Soap

Pure Castile Soap

Since I retired, I’ve offered to send readers my directions for making the pure castile soap I used to sell. There have been so many requests that I realized it would be better to simply put it on-line. So…here it is!

What you need:

• large deep and narrow 8-quart soap pot (enamel or stainless steel)
• plastic 2-quart pitcher for mixing the lye & water
• kitchen scale
• stick blender
• spatula
• wooden spoon
• two kitchen thermometers
• soap molds
• old towels or blanket
• old screen covered with white paper
• solid plastic or cardboard for covering the freshly poured soap (cereal boxes cut open work well)

Lye is caustic, so for safety: rubber gloves, safety glasses and apron.

Molds: I use Milky Way tray molds like these. A single recipe fills three trays; 18 bars of soap. I also have a loaf soap mold. If you don’t want to spend money on molds until you’re sure you enjoy doing this, do an on-line search for containers that people sometimes use.

Let’s get going…

Makes approximately 24 bars

52 oz. olive oil
7 oz. lye
20 oz. cold water (I use soft rain water; good for your hair & makes more suds)

Before beginning, find a flat surface where your soap can set up for a week or so. Cover it with an old towel and set your molds on top. Have your flat cardboard and more towels close by. Prepare the screen: I line up two chairs with the backs facing each other and a space the size of the screen between them. Use two yardsticks or something similar set on the chair seats and put the screen on top of them. Cover the screen with clean white paper. This allows air circulation on all sides.

  1. Using your kitchen scale, tare the pitcher’s weight, then add 20 oz. water.
  2. Weigh and tare a small bowl or jar, then add 7 oz. lye.
  3. Pour the lye slowly into the pitcher containing the water. Stir gently with the wooden spoon until the lye is totally dissolved. You’ll notice the water heat up – a lot!
  4. Clip one of the thermometers onto the edge of the pitcher; the lye solution will register 150-200F (66-93C).
  5. When the temperature has cooled to about 110F, begin to warm the oil.
  6. Tare your soap pot’s weight, then add the 52 oz. olive oil.
  7. Warm the oil on a medium heat with the second thermometer attached.
  8. The aim now is to have both the oils and the lye solution at about 100F.
    When that is accomplished…
  9. Carefully and slowly pour the lye solution in a thin, steady stream into the oil as you mix with your stick blender.
  10. Keep the blender going. The mixture will begin to thicken, turn opaque, maybe grainy, until…
  11. After 5-10 minutes, you’ll see trailings (also called “trace”) when you lift the blender and drip some lines of the mixture over the top of your soap. The trailings will stay put on top. They can be difficult to see.
Making cold process soap
The water/lye has just been poured into the olive oil & mixing begun
  1. It’s time to pour your soap into the molds! Scrape out every bit, but do it as quickly as you can while being careful (the lye is still active!). If you mix a bit too long, it can become too thick and difficult to pour.
  2. Cover your molds with the flat cardboard (it shouldn’t actually touch the top of your soap) and then two or three layers of towels or an old, folded blanket.
  3. Leave your soap for a few days, checking every day. When the surface is hard (depends on weather, but usually between 3 days and a week) it’s time to unfold.
  4. On a flat kitchen counter or other surface, turn the molds upside down and press the bottom of the mold to release the contents. Turn right side up and cut the bars apart with a pastry scraper or large knife. I find it helps to run hot water over the blade in between cuts.
  5. Put the bars on your prepared screen, leaving space between them.

In two or three weeks, your bars will be cured and you’ll have your own pure Castile soap! You can grate it to use for laundry soap, too. There are lots of recipes on-line.

Here’s an old post I made about saponification, and here’s one from 2013 with words and pics about making lavender castile soap.


6 Replies to “Jane’s Castile Soap”

  1. Natalie Abigail Samson says: Reply

    Thank you for a great recipe! I have a question please, would the measurements still be ok if i halved the recipe? Or even quartered the ingredients to test first?

    1. I assume that would be fine, Natalie. I’ve never made a smaller batch, but I always doubled it when I was making soap for my shop, and that was fine.

  2. DodgeCityLady says: Reply

    I just rub the bar soap in my wet hands then rug it all over the dog’s fur then massage the soapy bubbles into the fur. Don’t need much, and the bar will last a long time. If you rub the bar directly onto the fur, or onto your hair as shampoo, it wastes too much of the soap and takes longer to rinse out!

    1. I rub the bar over my dog’s fur and my own hair. However, if your method works, that’s great!

  3. Thanks for the recipe. Is there a way to make this into liquid soap? I’m thinking of making some dog shampoo.

    1. Liquid soap requires a different type of lye. Liquid soap needs potassium hydroxide (KOH), while bar soap uses sodium hydroxide (NaOH). Long ago I tried simply melting my bar soap with water, but it kept separating and the soap would solidify – not good.

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