Why and How of Curing Soap?

Why and How of Curing Soap?

What is a soap?

Soap is a salt produced by the chemical reaction, called Saponification, between fatty acids and an alkali metal hydroxide, such as sodium or potassium. During this reaction, the triglycerides are broken down into their component fatty acids and neutralized into salts by the sodium hydroxide. Cold Process Soap is the result of this chemical reaction.  

When we make soap, we are using water or milk to which we add the Lye (Sodium Hydroxide). After we make the Lye Solution, we add it to the oils. In this way the Saponification happens, and the result is the Soap. To be safe for our skin to use the soap, it must go through a process of curing.

What is Soap Curing?

When we are making soap, we use distilled water or milk to dissolve the Sodium hydroxide (lye), which is needed for producing the soap. When we take out the soap from the mold, it still contains water and lye. Therefore, the soap needs a period, called curing, to allow it to be in the best condition to be used. Otherwise, the soap bars will not last, turning to paste when they are handled.

Curing is the process of allowing saponification to complete and for water to evaporate out. In this way, the soap, is dry, harder, milder and the lye non-existent in the finished product. It takes about 4 to 6 weeks for a soap to dry and the lye to be totally transformed. The time we leave your soap to cure depends on the oils and percentage of water used in the recipe. When we use a recipe with discounted water, 4 weeks may be enough for the curing process. If we are making a soap with a more complicated design, such as a swirl, and we are using a recipe with larger content of Olive oil, then we wait for, at least, 6 weeks. Olive oil takes longer to be saponified and to harden up.

How is the soap cured?

After the soap is made, it takes about 24 to 48 hours until it is un-molded and cut.

Once the bars are un-molded, sliced and set on the shelves (racks), the curing period starts. 

The place where the soap is cured needs to be an airy, out of direct sunlight, and a dark place. These conditions will also help to preserve the scent. Sometimes, if we make more soaps and do not have enough room for them, we use stack-able metal racks.

Every couple of days we turn them for every side to be cured properly.

Metal stack-able racks for curing soap.

The link for stack-able racks:

https://candorasoap.ca/catalogsearch/result/?q=stackable+racks

On the shelves or racks, the soap bars have to be spaced, for the air to circulate around them. To be sure that we know exactly when the curing period is ending and when we must start packing our soaps, we add a curing card, to each batch of soap we make.

This template of the Cure card is offered           
           by https://www.modernsoapmaking.com/ .

We mark the soap’s name, the date when the cure period starts and when it ends, the total weight, and some notes.

Why is the curing process necessary?

There are a few things that can go wrong if the soap is not properly cured. First, it, still, contains lye. Even though the saponification of Cold Process soap is mainly complete in the first 48 hours, there is, still, a chance that the soap bars will contain lye for up to a month. To avoid skin or eye irritation, the handmade soap needs to go through all this period of curing before it is used. Also, the curing period will ensure that the bar of soap will last longer and will not disintegrate in contact with water.

Anyway, to have a handcrafted bar of soap for as long as possible, it is recommended to use a soap dish that allows draining, between uses.

Only after the curing process is ended the soaps can be packed and labeled. Otherwise, the condensation and moisture created by the un-evaporated water will destroy the packaging. 

Methods to reduce the curing period

Water discounting method means that we use less water to make our lye solution. For example: we can use more than 33% lye concentration for our soap. There can be use an equal amount of lye and water (which is the minimum amount of water), but this drastic water discount can be used only by advanced soap makers. The risk is, for a beginner, is that the high lye concentration will speed up the trace and the soap batter will harden, very quickly, becoming unworkable. 

Using a dehumidifier, in the place where we are curing the soaps, will reduce the curing period. If it rains a lot and the humidity is high, we use a dehumidifier in the space that we are making the soap.

When is the soap ready for using?

We always weight the soaps before we arrange them on the shelves. In this way, we observe, regularly, how much weight they lose. When they stop losing weight, it means that they probably are ready, and the curing period is ended. 

Some soap makers accelerate the curing setting their soaps outdoors, in warm and dry weather. Even if we would live in a place with warm and dry weather, I do not think that we will use this method because of the dust and impurities that may touch our soaps.

I hope that this blog gives you some insight into the timeline of the soap making process.