You can make your own shampoo in your slow cooker using this recipe

Eco 04/07/2019

If you are currently tackling 'Plastic-Free July', or just trying to decrease the amount of plastic in your life in general, then this recipe by Jane Wrigglesworth of This NZ Life is something that you should seriously consider.

While the recipe looks rather daunting from a glance, it is well do-able and is a great natural, plastic-free way to wash your hair.


slow cooker
digital scale that measures ounces and grams
heavy plastic containers
stainless steel or plastic spoons
stick blender
plastic wrap
rubber scraper
2 x 1-litre jars, with lids


As with making any soap, wear rubber gloves, eye protection, and closed-toed shoes.

If you get lye, lye solution, or raw soap on your skin, flush with cold water immediately, for 15 minutes. Germall Plus* is a non-paraben preservative.


Oil phase
This is the oil, butter, and glycerin combination that is melted together in the slow cooker on medium heat.
8oz canola oil
5.3oz coconut oil
1.1oz castor oil
0.8oz mango butter
0.8oz sunflower oil
4oz glycerin

Water phase
The lye solution is mixed separately and set aside until the oils are melted. Warning: potassium hydroxide is not interchangeable with sodium hydroxide (which is also known as lye and used in soap-making).
6oz apple cider vinegar (ACV)
3.9oz potassium hydroxide
(lye or KOH)

After Cook Ingredients

Superfat phase
These are added after the liquid soap paste reaches a petroleum jelly-like consistency.
0.5oz argan oil, or another superfat oil of your choice
1 tbsp liquid lecithin

Dilution phase
This is added after the cook and the addition of the superfat.
30oz distilled water, available from chemists, supermarkets and on Trade Me

2.4oz cetrimonium chloride (about 4%), an emulsifier that helps to soften hair

Cool-down phase
This adds in the fragrance and preservative, after some cooling.
0.2oz Germall Plus* or 5.7g which can be rounded up to 6g if your scales don’t measure 10ths
0.5oz/14g essential oil, best added while finished soap is still somewhat warm

3oz DL-Panthenol (about 5%, mixed with about 1oz water to dissolve) to help soften hair
2-4oz crothix, which makes the shampoo thicker

All ingredients are available online from soap-making stores.

It’s very important to measure ingredients by weight, for safety reasons, which is why you need accurate scales that measure ounces and grams.



Weigh oils, mango butter and glycerin and put them in your slow cooker. Cook on medium until melted.


Weigh out 6oz of apple cider vinegar (ACV) in a heavy plastic container. The container should be big enough that it is only about a quarter to a third full with the ACV in it as you need a good amount of head space.

In a separate plastic container, weigh out 3.9oz of lye (potassium hydroxide, also known as KOH). Pour the lye into the ACV. Use a stainless steel or plastic spoon to mix it.

This mixture gets very hot, bubbles up and will pop and spit, but it quickly settles.

Give it a quick but thorough stir when first mixing in the lye. 

When the oils are melted and the lye solution has cleared, add the lye solution to the melted oils in the cooker (which should still be on a medium setting). It's recommended leaving it on medium throughout the rest of this recipe.

Use a stick blender to stir and pulse the oil and lye solution mixture to ‘trace’. Trace is achieved when the soap thickens enough to leave a visible trail when you drizzle some of the soap off the blender and over the surface of the soap. For me, this soap comes to trace after about 10 minutes of bursts with the stick-blender. Don’t run your stick-blender continuously or you will burn up the motor.

Cover the cooker pot with plastic wrap so it is air-tight and leave it on medium.


During this stage, the soap is cooked until it reaches ‘vaseline’ stage. Your soap will become shiny and translucent — almost transparent, but not quite — and look somewhat like vaseline.

Every 15 minutes or so, remove the plastic wrap, then stick-blend and/or stir with a rubber scraper, then replace the plastic wrap.

The time involved can be oddly variable even when you follow this recipe perfectly. Normally this soap will reach the ‘vaseline’ stage after an hour. Sometimes it will take an hour-and-a-half. Once, when I had the cooker pot on high, it got to the vaseline stage in 10 minutes.

Note: you can have the cooker pot on high during the cook but keep a close eye on it. Alternatively, you can leave it on medium so you don’t have to watch it as closely.

When your liquid soap (technically, liquid soap paste) reaches the vaseline stage, it is soap and should contain no unreacted lye. This means that if a superfat is added at this point, it will not react with lye to become soap, but will remain in the soap as a free oil.

Some of this oil will remain on your hair when you shampoo with the finished product.

To check, you can ‘zap test’ it by touching your tongue to a dab of the soap. Some people say soap that has not completely saponified (chemically changed into soap) will ‘zap’ you like a small electrical shock. I find it just tastes like lye (bitter) instead of tasting like soap. The lye taste is unmistakable and very acrid. You will know.

Alternatively, you can use pH paper to test if it’s in the right range (pH 8.0-9.0). If the pH is more than this, keep cooking and test it again.


Add a superfat that you feel will benefit your hair. I’ve chosen argan oil for this recipe, but if you don’t have it, you could use olive oil or safflower oil.

Whichever superfat oil you choose, thoroughly mix 0.5oz of it with 1 tbsp of liquid lecithin in a small cup and add this to your soap (while it’s still in the slow cooker). Stir and stick-blend until thoroughly mixed in.

Leave the cooker on medium.


Weigh out the distilled water, and the cetrimonium chloride if you’re using it. Add all of it in one go to the cooker. Stir a bit, but it will not mix together much.

Cover your cooker with plastic wrap so it is air-tight and allow the soap to continue cooking on medium heat for another hour or two. After an hour or two, you will be able to see that it is slowly dissolving. You may want to stir it every hour or so.

Soap paste takes quite a long time to completely dissolve in water, generally 15-24 hours.

For the writer of the recipe, after the soap paste has cooked in the distilled water for an hour or two and is progressing nicely, she turns off the cooker and goes to bed for the night (it works out nicely if you have initiated dilution right around bedtime), or go out for the day, or just otherwise forget about it for a good 10 hours or longer. Be sure the cooker remains tightly covered with plastic wrap.

After 10 hours, check it. You will notice that most of the soap paste is dissolved. Use a rubber scraper to stir it a bit as usually there is some paste stuck to the bottom.

Turn your slow cooker back on to medium, replace the plastic wrap, and allow the liquid soap to continue dissolving with the aid of a little heat. This will take about four more hours of heating (and occasional stirring with a rubber scraper).

Once the soap paste is completely dissolved, you will have a clear, pale amber-colored liquid soap that is specially formulated for hair.


It is best to add a preservative to liquid soap. Germall Plus can be added when the soap temperature is under 122°F (50°C).

When adding fragrance to shampoo (bars or liquid), only use essential oils. Fragrance oils are bad for your scalp and hair.

The writer suggests using ylang-ylang and bergamot, or ylang-ylang mixed with a little orange or bergamot essential oils. Many like cedarwood essential oil, lavender essential oil, or a cedar-lavender blend.

Some essential oils make liquid soap turn runny. Ylang-ylang is notorious for making liquid soap runny but it is one of those fragrances that is worth it.

The best time to add essential oils to your finished liquid soap is when it is still a little warm. Use a rubber scraper and mix in 0.5oz (14g) of your preferred essential oil/s.

If you’re using a preservative, you don’t want a speck more than is necessary. Add 6g of Germall Plus, if you are using it. Mix it in thoroughly.

Your soap may turn a little cloudy when you add the preservative and/or the essential oil/s, but the cloudiness will dissipate quickly.

Liquid crothix is added after the soap has cooled to room temperature. If you add it to warm soap, you won’t see the thickening effect until the soap has cooled. If you add it to cooled soap, you will be able to tell how much is enough. For this recipe, 2oz of liquid crothix is adequate, but it takes 4oz to get it to the thickness I prefer.

Let the soap cool before you pour it into your storage container/s. Leave for 7-10 days before using. If you omit the preservative, store this shampoo in the fridge. Keep the soap covered and air tight.

This recipe originally appeared on This NZ Life.