Cold Process Soap - Making

Cold Process Soap - Making

There are few things as rewarding as creating handmade soap. It brings together chemistry and art in a way that lets your imagination run wild. Whether you want a pure and natural soap for sensitive skin, or a beautifully bright, colourful and fragranced soap; there is something for everyone.

The method below is very simple. It is all done at room temperature, so there is no need for thermometers and getting everything to the right temperature. And with this method, we chill the soap when it’s finished, rather than insulate.

Safety First

Because the soap making process requires us to turn soft butters and liquid oils into soap (a chemical reaction known as saponification), we need to add lye or Sodium Hydroxide (NaOH) to make this happen. There is no soap without lye.

Another term for lye is caustic soda and getting this on your skin or in your eyes will cause burns. For this reason, soap makers wear safety glasses & gloves, and ensure that all skin is covered. No bare legs and feet, in case of splashes. While using lye is not as scary as it sounds, it is still important to be safe rather than sorry.

Soap Queen has dedicated an entire episode here about safety when working with lye, we highly recommend watching it before you begin.


While you can spend an awful lot of money on soap making, there are a few basic things that you really do need:

Stick blender – vital for the soap making process
Plastic bucket – large enough to stick blend in (4.5kg is a good size)
Plastic jugs – soft plastic will last longer than rigid plastic
Saucepan – for melting solid oils and butters
Digital scales – precise measurements are essential in soaping
Spoons – solid plastic scoops are good for lye, metal spoons for design work
Spatulas – silicone, for scraping out the jugs at the end
Moulds - a basic silicone loaf mold is perfect when starting out


A basic soap can be made from minimal ingredients. The following is recommended for beginners:

Water - distilled or rain water is preferable
Lye ( for this recipe use Sodium Hydroxide)
Coconut Oil
Olive Oil
Castor Oil
Cocoa Butter

Fragrance - ensure it is one which will not accelerate (speed up) trace or you can be left with a solid lump of soap in your bucket, which cannot be poured. Some will also contain vanilla, which will discolour your soap. So using fragrances designed for soap making is always best and read the feedback, if available.

Colourants - there are countless options here, micas are an excellent starting point for beginners.

Formulating a recipe

A useful place for recipe creation is SoapCalc.

This is where you work out how your recipe will be when the soap is cured, how hard it is, how creamy or bubbly it will be and other important factors. As every oil has different properties, this is an excellent resource for product formulation.

For beginners, we recommend that you read the SoapCalc Directions (at the top of the page on Soap Calc Site), before you start. All you need to change at the top of the page is the ounces to grams section, when you’re starting out.


Now that you have your recipe, ingredients and equipment ready, it’s time to start soaping. Gloves, safety glasses and shoes on, before you start.

ONE: Make your lye solution first, it will need to cool to room temperature. Measure out the water into a plastic container, using digital scales. Weigh the lye into another container (remember the safety factors) and then add the lye to the water, never the other way around. Stir gently and set aside in a safe place.

TWO: Weigh out your solid butters and oils into a saucepan and melt over a gentle heat. Set aside to cool.

THREE: Weigh out the liquid oils and add with the melted solid butters and oils to your bucket. At this stage, you will need to leave everything to cool to room temperature. This takes a few hours, although you can speed it up in the fridge if you prefer.

FOUR: Once cooled, slowly add the lye solution to the bucket of oils and gently mix, before turning the stick blender on to start the saponification process. Use short bursts with the blender until it is well mixed and it starts to thicken slightly. This is called trace. Slowly add your fragrance oil and mix well with the stick blender turned off. This helps you avoid it thickening too quickly.

FIVE: At this stage you can add your colour to the bucket and blend again, or you can pour the batter into several jugs if you are using different colours. How much colourant you add depends on what you are using and how bright you want it, but move quickly as the soap can start to thicken. This is something you will get a feel for as you become more advanced at soap making.

SIX: Pour batter into the mold(s), scraping out the last of it with the spatula. Tap the mold gently on the bench to remove any air bubbles.

SEVEN: Smooth the top of the mixture or add texture for decorative effect then place the soap into the fridge overnight.

EIGHT: After 24-48 hours it will be ready to remove from the mold and be sliced into pieces. You can use a large knife, cheese cutting wire or soap cutter to do this. If it’s not quite firm enough to slice, leave another 24hrs and try again.

NINE: Leave the soap slices to cure for approximately one month. This allows the water content to evaporate off and makes for a much harder bar. Leave room around each slice for air flow.

Leave the dishes for a day or two before cleaning up, as initially it will be raw (caustic) batter but after a while will be soap and much easier to deal with!

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