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Homemade Pure 100% Olive Oil Castile Soap

Castile soap

Castile soap

Castile soap is among the soap classics. Mild, gentle, and nourishing to the skin, it is suitable for bathing babies and cleansing sensitive or dry adult skin.

One good reason to make your own: If you read the labels on many commercial “Castile” soaps—even those sold in health food stores—you will find that they are not made with 100% olive oil, but with some combination of vegetable oils. The real thing is quite something else! It’s also fairly inexpensive to make, if you buy Wal-Mart’s large, economy size olive oil. Mine calculated out to about $1.15 per bar.

Another reason to make your own Castile soap is that it can be used to make an excellent homemade, all-natural shampoo. While my experience is not extensive, I’ve found that real, pure 100% olive oil soap works best in homemade shampoo. (See this link for directions:

When making soap with 100% olive oil, it’s best to use a “water discount.” That is, the amount of water in the recipe is reduced. Some lye calculators, such as, allow you to select the oil-to-water ration you feel will work best with a particular recipe. This recipe has a water to oil ratio of 30%.

At the bottom of this page you can view a screenshot of the details on this recipe, provided by, a popular online lye calculator.

Most experienced soapers feel that 100% olive oil soap must complete the gel phase. This means it will be slightly translucent and a very pale greenish color—not the pure white that some recipes claim you will get.

You can get a pure white 100% olive oil Castile soap, by not allowing the soap to go through the gel phase, but this would produce a hard, crumbly, and inferior quality soap.

This recipe is fragrance and color-free. You can add fragrance and soap colorant at trace, if desired.


Olive Oil 32 oz.

Water 9.6 oz.

Lye 4.1 oz.

Yield: About 46.7 ounces, or 2.9 pounds soap.

Follow basic soap-making directions below. Unmold and cut the soap after 8-10 hours. (This soap hardens pretty fast.)

How to Make Soap

The way you make soap is this:

1. Weigh the oils or fats you have selected and put them in a deep plastic, stainless steel, or ceramic container. (Most people use a crockpot. Do not turn it on, or even plug it in.)

Measurements are by weight. You will need a kitchen scale. You can often find these at thrift stores. A digital scale is nice, but an ordinary kitchen scale works fine.

2. In a separate plastic container, weigh lye

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3. In another container, such as a water glass, weigh water.

4. Pour the lye into the water and mix with a stainless steel or plastic spoon until lye is dissolved and the water is clear and has cooled to lukewarm.

5. Now carry your lye and water solution over to your crockpot and add the lye, pretty much a little at a time, while mixing with a stick blender.

6. After a time period ranging from a few seconds to a few minutes, your mixture will begin to take on a pudding-like consistency. If you trail a little of the mixture across the surface of the mixture, you will be able to see a trail. This is called “trace.” Stop mixing—at least with the stick blender—or soap may get too hard.

7. If you are using color and/or fragrance, hand mix these in now. You can still use the stick blender to make sure everything is well blended, but do it sparingly.

8. You can now pour (ladle) the soap into molds. Quart-size milk cartons work well and do not need to be lined with anything. Many people use empty Velveta boxes, Pringles cans, or cardboard boxes, but these must be lined with freezer paper.

9. Once the molds are filled, wrap them in towels or blankets to insulate. This is important. I feel that most soaps should go through the complete gel phase, which can only be accomplished by keeping them warm.

10. When the soap has hardened well, remove from the molds and cut into bars. This usually takes about 12-16 hours, but you never know for sure. Depends on the recipe. Soap will still be caustic when you cut it. Wear rubber or plastic gloves.

11. Once soap is cut into bars, you should be able to use it after only 48 hours (that’s if it heated up well in the molds, was well insulated, and hence completed gelling). But soap should be allowed to cure for 3-4 weeks after cutting, to allow the bars to harden so they last longer.

I usually try out the soap with small bars formed from pot scrapings and from cutting slivers off the ends of the loaves to get rid of marks left by the molds.

Soap-Making Safety Precautions

If you read the label on the lye container, you will see that it is labeled as a “caustic poison.” It will burn your skin, mar some household surfaces, and even eat through glass over time.

The lye, lye and water solution, and the soap mixture (for about 48 hours) will burn your skin if you get any on you. Wear rubber or plastic gloves and eye protection when making soap. Long sleeves are a good idea too. Before you begin making soap, it is a good idea to pour some white vinegar in a bowl and set it somewhere handy. If you happen to splash soap on your skin, splash the spot with vinegar and rinse well.

There is nothing to be scared of here. You are no more likely to hurt yourself making soap than you are to hurt yourself deep-frying. You would not touch heated oils for frying, and some splashed on you, you would handle it. The same with lye and anything it’s mixed into.

A stick blender is normally used to mix soap, partly because it brings soap to trace very quickly, and partly because it does not splash soap around, if used properly.

I have made soap with an electric hand mixer. If you simply can’t wait until you can get to Wal-Mart for a stick blender, this will work—but you should do it outdoors and be suited up Hazmat-style. Electric mixers splash—big time. An electric mixer also takes quite a bit longer to bring soap to trace.

While soap can be mixed by hand, this may take a long time—possibly a very long time, depending on the oils/fats used. I’m talking hours.

Some Tricks for Making Sure You Get Complete Gel

So-called “partial gel” in soap—where the middle portion of the soap is darker and more translucent than the outside portions—is harmless and in no way diminishes the quality of soap, but is a cosmetic issue. But obviously you want to make beautiful soap without any cosmetic defects.

Getting complete gel every time, with every soap recipe, was something I struggled with at first.

Here are some ways to make sure you get complete gel every time:

After the soap is poured into the molds, wrap it up in towels and blankets. Two layers of thick bath towels may not be enough. If you are using quart milk cartons, for example, both the top and the bottom ends may still be too cool to gel completely, and you may notice a thin line of ungelled soap around the outside of the soap, when you remove it from the molds.

You could solve this by adding more coverings.

Another solution is to preheat your oven to the lowest possible setting—about 170 or less—turn off the oven and slide in the soap molds, wrapped in two bath towels. Use old towels. Even if you are careful, they are likely to get scorched. Be sure the towels cover the bottom of the molds completely. With tall molds, like milk cartons and Pringles cans, you will want to set the molds in a pan or bowl with high sides, so they don’t fall over.

My preferred method is to set the soap mold on a heating pad set on medium, cover with a cardboard box, and cover the box with a blanket or comforter. For most soaps, leaving the heating pad on medium for two hours ensures gel.

The soap will need to remain in the mold until it has cooled and hardened--probably 18-24 hours.

Cutting the Finished Soap

Many people cut their soaps with a sharp knife. A knife with a thin blade works best. An inexpensive miter box can be a help in getting more uniform cuts. I find that I get the best cuts using fishing line and a miter box. Probably best of all are specially crafted soap cutters, but these are expensive unless you can make one yourself.

This is a screenshot giving details of this recipe, provided by, a popular online lye calculator.

This is a screenshot giving details of this recipe, provided by, a popular online lye calculator.


Sharon Vile (author) from Odessa, MO on August 29, 2020:

The soap comes out pure white (or close) if you use pure olive oil--the Walmart "Great Value" brand in the gallon-size bottle. It does stay greenish until it's saponified, so it's hard to judge the colors while you are making the soap.

I prefer mica colorants, and one of the best suppliers is

Mica colors are normally added at emulsion or trace. I think there are some natural colorants that should be added to the lye water, such as indigo. (Natural colorants often seem to have some finicky requirements.) With micas, what you see is what you get--pretty much. They may fade or brighten during saponification, but they won't turn into a whole 'nother color.

Roberta on August 29, 2020:

This Castile recipe is a winner. Easy to unmold, picks up details nicely, comes to a trace quickly is cheap to make. Years ago I tried a pure olive oil soap and it was a disaster.

My only question is what to use as a colourant? If you use cheap pomace olive oil the colour is murky green. Any suggestions? And while we’re on the subject, is it better to add colour to the lye water or to the mixture at trace.

Linda Crampton from British Columbia, Canada on October 01, 2014:

I like the sound of this recipe. The finished soap looks lovely. Thanks for sharing the instructions.

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