Before You Begin, a Brief Introduction to What is Soap

Before You Begin, A Brief Introduction to What Is Soap

Making soap can be tricky when you are first starting out on your soap making journey.

This is because the chemical constitution of soap is a complex thing, but once you understand the basics you can have great fun getting creative and learning how to make soap.

What is soap?

In order to understand this, we need to get a bit technical.


Every oil has its own unique saponification value. What this value means, is how much sodium hydroxide is required in order to turn oil into soap.

What is happening chemically, is that the fats, oils, sodium hydroxide, and water are all reacting together. This reaction creates glycerin and soap – which is a process known as saponification, as you begin to add these ingredients together, the mixture starts to change into a thick, uniform texture.

Once the soap can be drizzled from the spatula to leave a pattern on the surface, the mixture is ready to be poured. This is known as trace, where the ingredients have been evenly dispersed to create a thick, stable emulsion.


This is also called a “lye discount”, super-fatting means to leave the oil in the final bars, which helps to create a mild bar of soap.

This can be achieved one of two ways:

  • Either by reducing the amount of lye by 5%
  • Or by adding extra oils

Deciding what percentage of oils to add can be tricky when starting out. If you want your soap to be really creamy, you can go up to 3%.

Once your basic calculations have been calculated, you will need to establish how much lye you are going to require in order to create your homemade soap recipes. You can then deduct 3% of that amount.

Some people add the super-fatting oils during a trace; I find the best way to super-fat is to add all the oils together in the soap pot, including the super-fatting oil, by simply calculating the lye, deducting the super-fat percentage, and then adding the lye to the oils, you are completing everything all in one go, which creates a great bar of soap.


It is important to use spring or distilled water. Exactly how much water is used tends to vary from person to person; I recommend using 33% of the total weight of oils, which produces a really nice even mix, this will also give you time to add any Essential Oils and Herbs, without having to rush.


  • Once the oils have achieved trace, they have reached the stage where the ingredients have thickened enough to add the Essential Oils
  • At this stage, the mixture should be smooth with no lumps – but be warned, if you do see watery or oily puddles in the mix, this signals a poorly-mixed solution
  • Another tip when pouring the last bit of soap: if it does look too watery and uneven, don’t add it, as it may contaminate the rest of the batch
  • If you don’t pour quick enough, and the mixture starts to set unevenly, use a spatula to spread it out to the corners. You can then add them it to the mould


In order for the water to completely evaporate, soap needs curing. To do this you need a dry, well-ventilated area; one that is protected from extreme temperatures.

Once you have poured your mixture into the mould, cover with a blanket or a piece of heavy cardboard and leave undisturbed for twenty-four hours, this curing process is really important, as the insulation allows the soap to heat up and saponify further. Once this has been done, lay the bars on a tray with spaces in between them, turning them every so often to fully expose both sides.

Soap needs to be left for six weeks in order to become dry, hard, and mild. If you do attempt to use the soap before this time, they won’t cure properly and could potentially irritate the skin.

Another important tip is to not wait until the soap is rock-hard to cut into slices; the soap will be impossible to cut and will crumble. Instead, try to cut the bars immediately after the insulation period.

If you want to learn more about what soap is and the chemistry behind it, this article from lab muffin is an interesting read.

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