How to Make Cold Process Soap

Cold Process soap making can appear daunting from the outside, but once you learn some basic safety needs and techniques it will seem simple and you will wonder what all the fuss was about.

Cold Process Soap Making Instructions


These instructions are intended for use with any soap recipe such as the many available on this website.

Soap making is a time honoured occupation that goes back centuries. Techniques have changed a lot since the original methods, but the basics are the same – the combining of fats, oils and a caustic medium in the presence of water.

Cold process soap is made by heating fats and oils to melt them, we do not actually cook the soap. If the soap is cooked on a stove, oven or crock-pot it is referred to as hot process.

Soap making is much like cooking. We have ingredients, a recipe, we have pots, pans, bowls, spoons, moulds and safety equipment.

Ingredients for most soap recipes need to be weighed, not measured.



Apricot kernel oil – A luxurious oil that adds conditioning assets to your soap, but use in moderation.

Caster oil – a small percentage of this oil will add to a wonderful lather with added conditioning properties.

Cocoa butter – a special oil that conditions, aids good lather while making a hard bar of soap

Coconut oil – adds to a good lather with lovely bubbles in a hard bar

Grapeseed oil – is a great conditioning addition to a recipe, but too much will make for a soft soap

Lard – is conditioning while making a harder bar of soap than most vegetable oil soaps and has good lather.

Macadamia Nut oil - a nutty scented oil that will add conditioning properties to your soap

Olive oil – a wonderful oil that can be used alone or in combination recipes. An all olive soap takes much longer to cure than a mixed oil recipe but can result in a bar as hard and lasting as one with animal oil components.

Palm oil – makes an excellent addition to soap for hardness and conditioning capabilities with lovely lather.

Shea Butter – a conditioning oil that makes a good hard bar with a nice lather.

Sweet Almond oil – a wonderful conditioning oil in moderate proportions

Tallow – makes a harder bar of soap than most all vegetable soaps

Lye - is known in this country as caustic soda and can be found in the laundry aisle of your supermarket or hardware store near the drain cleaners and borax. Make sure you read the label very carefully to ensure that you get the product that is at least 98% sodium hydroxide as other products have metal components that we do not want in our soap.

Water – Distilled water is best to use, but rainwater, filtered water, or even good tap water can be used.


The main difference between cooking and soaping is the caustic factor. Never use aluminium utensils as the caustic slowly dissolves the metal and you have aluminium in your soap. Wood isn’t too good either as it falls apart after a use or two and can leave you trying to pick splinters out of your soap before it sets. Plastic and stainless steel are the best items to use as they are non-reactive. Due to the caustic you must wear goggles to protect eyes from accidental splashes, an apron, and gloves as hands are an easy target. If you do happen to get caustic on you use vinegar to wash the affected area, or if it is in your eye flood it with water and visit the local hospital if you feel it is necessary.

It is in your best interests, and those of your family to make soap when children and pets are not around to interrupt your train of thought, or lick out the pot when you are not looking. If a child does happen to eat some of your soap while you are making it get them to drink orange juice and get them to a hospital.

Making soap

The first thing we need to tackle is the weighing out of your ingredients. Put on your goggles, apron and gloves

Weigh your oils first and set them to melting as they take the longest to cool. When they are nearly all melted remove them from the heat.

Next, measure out your water into a plastic container, and your lye into a smaller plastic container. Take your water, lye and spoon outdoors if possible as the aroma can be a little unpleasant. Pour your lye into the water slowly and stir until it is dissolved. Try not to breathe in at this time. Put it in a safe place to cool.

While your pots are cooling prepare your additives if you wish to use them. These can be clays, liquid colours, ultramarines, oxides, botanicals (eg lavender flowers, oatmeal, dried orange peel, spices…)

A lot of these will go brown when added to soap, although a few will hold their colour. Trial and error works well, but good research of your chosen item will save a lot of heartache.

Measure out your fragrance and add it to your botanicals if you are using them. This can often help to anchor fragrances that may fade otherwise.

When both pots have cooled to about 40C you are ready to combine your pots. (This may not happen simultaneously.) If a pot is too cool put it in a sink of hot water, or a cool one if it is too hot. Juggle the temperatures until they are about right.

Gently pour your lye mix into your oils in a slow constant stream as you stir the pot carefully with the plastic spoon in the other hand. When they are mixed bring out the artillery. A stick blender is an invaluable tool for a soap maker. Hand stirring works well, but takes a lot of time. A hand stirred batch of soap may take several hours to reach its end. A stick blender cuts this down to a few minutes.

What you are looking for is known as “trace”. It is a thickening of the soap that resembles really thick custard. When the stick blender or spoon leaves an impression on the top of the soap for just a moment it is said to have reached “trace”. It has thickened to the point where it can support some of the mixture on its surface before it sinks to the general mix. Don’t be too afraid you won’t recognise this. Once you have seen it you will notice it more readily next time. Trace will start off quite thin, but will thicken as time progresses and eventually become solid. Once you have reached trace, work with reasonable safe speed. Add colorants, fragrances and botanicals at this time. For a swirl effect add your fragrance and botanicals if you are using them and mix well. Blend your chosen colourant with some soap and add the colour last, stir round once and pour into your moulds. For all over colour add all extras and stir well with your spoon before pouring.

Place moulds in a cool oven with the light on, or wrap carefully in a towel or a blanket to keep the heat in. The chemical reaction-taking place within the soap generates heat that needs to remain for a few hours to complete the transition. If it cools too quickly the process may not be properly completed. In warmer weather it is not such an issue, but on cooler days with small moulds it may cause problems.

In 24 hours the soap may be unmoulded. This soap will still be a bit soft and still mildly caustic. The final stages of saponification take about a week to complete, and then needs a further three week minimum curing time to allow enough water to escape for the soap to last any length of time. If you are desperate to try your creation have a quick lather at the end of the first week, but I recommend leaving it to complete the cure before putting it to work full time.

Once you get the hang of soap making you may wish to venture out to new recipes or create your own recipes up using ingredients you would prefer. There are quite a few books on soap making available in shops and from the local library. If you wish to make up your own recipe make sure you put your ideas through a lye calculator such as the online version that can be found at .

To use this you put in all your fats and oils and ask it to contribute the water and lye quantities for you. This can then be printed out and used for your own purposes. Make sure any recipe you find is put through a lye calculator, as sometimes errors are made in recipes that can have less than desirable results.

We wish you every success with your soaping. Take your time and enjoy it.

by Kerry Pearson
Heirloom Body Care

  • Published In: How To...
  • Created Date: 2014-07-22