Basic cold process soap tutorial

Difficulty: Intermediate
Time: 1 hour
Yields: 500 g soap

Lemon soap

Making cold process soap is a more advanced technique, so if you have never made your own cosmetic product before, I suggest you start with a melt & pour soap or bath bomb tutorial first.

Before starting, please read the safety and precautions post, especially since this tutorial requires the handling of caustic soda!

Cold process soap making is one of the most popular soap techniques. Cold process means that there is no heat added to the process of soap making. As opposed to hot process soap making, during which the soap is cooked to speed up the saponification process (turning the oils into soaps). The heat in cold process is produced only by the chemical reaction. You can control this heat during the first 12 hours of the curing phase by insulating the soap, but this is a rather advanced technique, therefore in this tutorial we will work with our oils and lye at room temperature and leave the soap to cure without heat control.


The equipment you need for making cold process soap

  • heat proof glass jugs i.e. Pyrex
  • stick blender
  • digital scales at 1g increments
  • a 1 litre empty milk/custard/soup carton (I’m using a 1L Campbell’s soup carton)
  • plastic or silicon spatula
  • whisk

You can buy your material from the Warehouse or Briscoes.


Ingredients you need to make soap

  • 100g olive oil
  • 125g coconut oil
  • 100g rice bran oil
  • 25g castor oil
  • 50g caustic soda (sodium hydroxide NaOH)
  • 120 ml water
  • 10 ml essential oil

This recipe is comprised of olive oil, coconut oil, rice bran oil, and castor oil. All the recipes featured here on In My Soap Pot are palm free. This recipe is an alternative formulation to the usual coconut/palm/olive trio in soap making, but will still produce a nice solid bar of soap with a rich creamy lather. These oils all offer something different to the soap. Coconut oil will give the soap firmness as well as a large lather. Olive oil is very gentle cleansing but reduces the lather in soap. To make up for this, I’ve added castor oil, which produces a rich, creamy lather in soap. Rice bran oil is added for its skin conditioning properties, which prevents the soap from becoming too drying out to the skin.

This recipe contains a 5% superfat., which means that 5% of the oils in will not be turned into soap, and are “free floating” in the soap. Superfatting is one of the reasons why handmade soap is less drying to your skin than commercial soaps.


Caustic soda is used for drain cleaning, which is why you’ll find it in the cleaning section at Bunning’s Warehouse (Mitre 10 has stopped stocking pure caustic soda). This brand pictured above even tells you that it’s ‘perfect for making soap’. I do wonder if it is bought more often for this purpose than the actual drain cleaning!

If you can’t find this brand, make sure you buy a caustic soda that contains at least 98% pure caustic soda. The other 2% are an additive that prevents the caustic soda from clumping together. A bit like the tapioca starch in icing sugar.

If you live in or near West Auckland, you can also buy your caustic soda directly from Pure Nature, but because of it is classed as a chemical hazard material, you can only pick it up from their warehouse in Henderson (no shipping!).

Cold process soap making

There are three main steps in soap making. First, you need to prepare your lye solution. Then, you need to weigh out your oils. And lastly, you pour the lye into your oils and stick blend it to soap. Soap making isn’t complicated, but it does require you to work accurately and safely. And although this is a simple soap recipe, it will teach you the necessary skills to continue on to more advanced techniques. Many beginner soap makers become discouraged because they attempt difficult and advance soap and colour work. Start with the basics and then you will be able to progress in no time!

SAFETY FIRST: If you haven’t done so already, please read this post about safety and precautions when handling lye and caustic soda. Gear up!

PREPARE: Before you start, it is helpful to have your material and ingredients set out. You don’t want to be running around looking for batteries for your scales or realising you’ve run out of olive oil!


ONE: Fill a heat proof glass jug with the required amount of water from your tap. Since, most water in New Zealand is considered soft, there is no need to use distilled water, although I do suggest to use filtered water if possible. Weigh out your caustic soda and slowly and carefully add the caustic soda to the water. Gently stir, avoid splashes, until the caustic soda has fully dissolved and the liquid is clear. This is now called lye (water + caustic soda). Place in sink and leave to cool down to room temperature. You will notice that the lye will get very hot and give off fumes. Make sure you don’t breathe in the fumes!


TWO: Weigh out your coconut in the large Pyrex jug (or other heat proof glass jug) and place the jug in the microwave for approximately 60 seconds on high, or until the coconut oil has melted. Alternatively, use a large stock pot (cheap ones are available from the Warehouse) and melt the coconut on the lowest setting on your stove. Weigh out the other oils and combine with the coconut oil. Set aside to cool down.


THREE: Let both the prepared lye and the oils cool down to room temperature (around 25 degrees C). You will want them both of them to be similar temperature.  You can tell when the outside of the jugs feel cool to touch. They will be at approximately the right temperature. Gently pour the lye into the pot of oils, avoiding any splashes. Place your stick blender into the oil/lye mixture and start pulsing (turn on the stick blender for about 10 seconds and stop, stir the mixture, and turn on again for another 10 seconds, and so on). When the mixture has turned a runny custard like colour and consistency, and you can see no oil trails in the mixture, your soap mixture is ‘at trace’. This is when all the oils and lye have been blended together and saponification can occur evenly throughout the soap.


FOUR: Add your essential oil or fragrance. If you are using fragrance, make sure it is skin-safe (candle fragrances are usually not safe for use in cosmetics). If in doubt ask your supplier! Give the soap mixture a good stir, to mix in the fragrance completely. Do this when your soap mixture is at thin trace. Some essential oils and fragrances will accelerate trace!


FIVE: Once your soap has reached trace, pour it slowly into the mold. Try avoid bubbles and gently tap the mold on the bench a few times to remove any bubbles that are in the soap. The tapping will help the bubbles come to the surface. Let the soap sit in the mold for a few days, before unmolding. If the soap is hard enough, cut into bars, otherwise leave to soap for another few days before cutting. Allow the soap to cure for another 4-6 weeks to finish the saponification process (turning the oils into soap) and to fully harden. The longer you leave it to cure, the harder and longer lasting the soap will become.


Basic Cold Process Soap

  • Difficulty: intermediate
  • Print
Before starting, make sure you wear protective goggles and gloves and work in a well-ventilated area, free from any distractions!


  • 125 g Coconut Oil
  • 100 g Olive Oil
  • 100 g rice bran Oil
  • 25 g castor oil
  • 50 g sodium hydroxide NaOH (caustic soda)
  • 120 g water (distilled if you have hard water)
  • 10 ml fragrance or essential oil of your preference
  • heat proof glass jugs i.e. Pyrex
  • stick blender
  • digital scales at 1g increments
  • a 1 litre empty milk/custard/soup carton (i.e. Campbell’s Soup)
  • plastic or silicon spatula
  • whisk


  1. Measure out the water in the smaller heat proof glass jug (i.e. Pyrex) and weigh out the caustic soda. Slowly and carefully add the caustic soda to the water and gently stir until all the granules have fully dissolved and the liquid is clear. Set in the sink to cool. This is now called lye (water + caustic soda).
  2. Weigh out the coconut oil in a heat proof glass jug (i.e. Pyrex) and heat on high in the microwave for 60 seconds or until the coconut oil has completely melted. Weigh out the other oils and combine with the coconut oil.
  3. Once the lye and the oils have cooled to room temperature, carefully add the lye to the oils and stick blend in 10 second pulses until all trails of oils have disappeared.
  4. Once the soap is at a thin trace, add the fragrance and mix in completely.
  5. Carefully pour the soap  in your mold. Keep the soap in the mold for 3-4 days before cutting, and then cure for a further 4-6 weeks.

Where to buy your ingredients and material

  • Pyrex jug, scales, stick blender, whisks and spatulas can be bought from Briscoes or the Warehouse
  • Disposable gloves are available at most supermarkets
  • Bunnings Warehouse stocks caustic soda as well as protective eye goggles
  • You can buy olive oil, coconut oil, and rice bran oil from your supermarket
  • Castor oil can be obtained from your pharmacy (you only need a little bottle)
  • If you are located in or near West Auckland you can buy your caustic soda from Pure Nature, as well as all your other oils and essential oils for this project
  • Pure Nature, Go Native and Candle Creations also stock essential oils and soap fragrances. These are cheaper to buy from these places than at the pharmacy.

Author: Jackie

Mum, blogger, soap maker, frequent flyer!

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