11 Easy Ways To Harden Homemade Soap

The most frequent question new soapmakers ask is, how long does it take for soap to harden? Or what is the best way to harden my soap? So today, we will be answering these very questions.

Soap hardening is a crucial step in the soap-making process. The hardness of the soap determines its durability, lather quality, and how it feels on the skin. While there are natural methods to harden soap, such as curing it for several weeks, there are also technical methods that can expedite this process.

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As a new soap maker, waiting to try out your new soap is something many in the beginning struggle with. But, in soap making, patience is key to having an exceptional end product and a product that lasts long.

So, the hardening stage is essentially one of the most critical parts of the whole process. How to do it and how long you need to let your soap cure is, therefore, is a very crucial question.

How long does it take for soap to harden?

Curing your soap means letting the water in your soap evaporate, and the less water in your soap, the harder it will get. This does not mean that all soap needs a long time (or a short time) to cure. It means that all soaps need to go through that process in order to harden. However, this may take a long time with some soap, and with others, it may not.

A common misconception is that all soaps are the same, and therefore, they all need a long curing time. Indeed, many soaps need more or less the same curing time, which is around 4 to 6 weeks, but this heavily depends on the oils you have used.

To give some examples, soaps that are high in olive oil usually take around 6 weeks or a little longer to cure, while soaps made with other oils may need not more than 4. Or on the other end of the spectrum, you have castile soap which can take up to 1 year to cure.

There is also the hardness feel that may be different for everyone. You might feel that soap is hard enough, while the one next to you would need it to be just a little harder.

Why is my soap not hardening?

Most of the time, it’s the recipe that causes your soap not to harden. However, it also may be possible that you did not really have trace (or had a false trace), which caused your soap to not go through the saponification process properly. It also may be possible that the oils you used were too soft and that your soap simply needs a lot of time to harden.

The best way to avoid this is to always use a soap calculator before starting a new recipe. This way, you are safe when it comes to measurements.
Secondly, when it comes to soap trace, one way to know for sure that you have reached trace and not one that looks like it is to stop mixing and waiting to see if the mixture is losing trace or has developed an oily sheen.

When it comes to the wrong measurements, such as not enough lye, it means you used too much water, and therefore, the oils and lye cannot saponify.

There is also the possibility that you used too many soft oils and not enough hard oils (like coconut oil or palm oil, for example). If that is the case, it means your soap needs much more time to harden compared to other recipes.

Finally, if your soap simply needs more time to harden, you need to be careful with DOS (Dreaded Orange Spots). The downside of letting soap cure for a very long time is DOS. By itself, DOS is not really a big deal if it’s for self-use, but if you are planning on selling them, you can’t if it has DOS.

How do you know when soap is done curing?

The next time when you have just finished making your soap and are at the point you want to let it cure, weigh it. If you weigh it every day from that moment on, you will see that it loses weight each day (this is the water evaporating), and when it stops losing weight, you know that it is most likely done curing.

Just to let you know, that is not a 100% sure-fire way to know that your soap is done curing, but it helps you understand how long more or less your soap needs to cure. The more soap you make, the more experienced you become, and this way, you will be able to modify the cure time of each recipe you have.

Shortening the curing process is not that easy.

There are ways to manage the curing time of soap and even shorten them. However, this is something that should not be done by a novice soap maker, especially if you have not done any course on making soap. It takes a meticulous calculation and technique to do this, and you can easily make mistakes, which will end up with a failed batch.

An example:

You can do this by using a water discount. This means that you use less water than what the recipe recommended, and thus you’d need less time for the water to evaporate and fully cure. But having less water in soap also means you’d need a different temperature (higher) for it to fully gel, and most novice soap makers are not aware of this.

Here are eleven ways to harden your soap faster and harder

1. Using A Water reduction

As previously mentioned, water reduction is a great way to shorten the cure time of your handmade soap; however, you’d need to know what you are doing before starting jumping to this. Water reduction can also help get harder bars; actually, they go hand in hand.

So since you are using less water, the soap bar would logically also get harder in a shorter time, and if you were to wait the same amount of time that you would typically wait without the water reduction, you would end up with a harder soap.

2. Adding Soy Wax or beeswax

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Adding a small amount of beeswax (or, in case you wish to go vegan like me, soy wax) also helps harden your soap. However, they are a bit tricky to work with, similar to water reduction. This means you need to soap at hotter temperatures compared to the typical temperatures you are used to. At the same time, you are making sure the wax does not solidify.

So, I would suggest trying a small batch to see if you are successful and moving on to a bigger one afterward. As to the amount of soy wax to use, it’s recommended to go for 1/4-1 teaspoon per pound of oils. However, the amount differs depending on the recipe. 

3. Add Some Sodium lactate

There are two benefits to using Sodium lactate. First, it helps to get your soap harder, and second, it helps to unmold your soap faster (around one day earlier). Believe me, once you go sodium lactate, you’ll never go back. Why? Because this clear liquid that comes from the natural fermentation of sugar cane or sugar beets is really a wonder product when it comes to getting your soap harder.

You add sodium lactate to the cooled lye water. This means you need to wait until the lye water has reached temperatures of 130 °F or below. Only once you have reached the optimal soap-making temperature can you add your sodium lactate. 

4. Adjust your recipe to 40% hard oils

I mentioned a few times the need to have hard oils or butter. And a good baseline on how much a recipe needs in order to be able to harden fast enough is around 40%. You have a lot of options, so it should not be a problem to find a substitute. Just make sure to check the SAP value of the oil you want to use and the substitute’s SAP value.

A good example, in this case, is olive oil, its SAP value is near to many other oils, and thus, you could use olive oil as a substitute in a lot of recipes. However, if you want to use coconut oil, the SAP value is much different, and you’ll have a hard time using it as a substitute.

5. Adding salt

Similar function as sodium lactate, salt helps your soap to get very hard. The recommended amount of salt depends on the recipe, so you will need to check how much salt you need for each recipe.

However, I can tell you that the salt should be stirred into the Lye solution well; this means it needs to dissolve before you mix the Lye solution with the oils fully. Also, it is crucial to use pure salt (so it cannot have any additives). Using a “none pure” salt may affect the outcome of the soap bar. 

6. Using Stearic Acid

Stearic acid is mostly used as a thickening agent in lotions, but it is also ideal for speeding up the hardening process and getting harder bars. One thing that you need to remember is when using stearic acid is that it speeds up trace, so you need to keep it in mind and also use a hotter soaping temperature (minimum 160°F) so it stays melted.

Also, the amount you need to use is minimal; it’s around 0.5% of your oils. This amount may sound very small, but just a little is enough to get the job done. 

7. Check your superfat

Sometimes you need to superfat your soap to make it moister. However, superfatting may prevent your soap from hardening. Of course, if you decrease superfat, you might end up with a soap that irritates the skin. A good balance is around 5%. This is the ideal firmness and, at the same time, still good for the skin. 

8. Thicken the trace of your soap

We’ve already discussed the importance of trace and how to notice a false trace but, in order to get a good final product, you need to take your time; trying to get things done quickly in soap crafting is impossible.

A good trace in this context means a thick trace. If you wish to have your soap harden faster, you need to pour your soap into the mold when your trace is thick.

9. Using an accelerating fragrance oil

Some oils like Lemongrass and Cinnamon oils cause faster trace and also help the hardening process in the mold. The difference you gain may not be as helpful as the other options since it only causes faster trace and hardening in the mold, but I thought it was still worth mentioning. There is also the problem with the fragrance type and smell that is limited.

10. Get a dehumidifier 

Humidity in the air is your biggest enemy when it comes to curing soap. If there is a lot of moisture in the air, your soap will sweat, which means that it will absorb moisture. And yes, as you have probably guessed, the more humidity, the longer it will take for your soap to cure.

To help counter this, you may be able to use a dehumidifier. Just a quick note, the room you are letting them cure still needs to have really good airflow, so using a dehumidifier does not mean you can leave your soap out in the open or under the sun. 

11. Using an electric fan

To help accelerate the soaps curing process, you can use an electric fan. Any fan will do as long it blows air at a constant pace. This method can only be used by someone who has already made the soap and knows the final weight after curing. I am saying this because it can go really fast and you’ll need to check the weight very regularly.

The science behind soap hardening is fascinating. When soap undergoes the saponification process, the combination of fats and lye leads to a chemical reaction. The rate and efficiency of this reaction can be influenced by various factors, including the ingredients used and the methods applied. By understanding these factors, soap makers can achieve the desired hardness and texture in their products.

How do you make homemade soap last longer?

The best tip I can give is, do not let your soap sit in water. I know this sounds so obvious, but you need to know that homemade cold process soap is much more prone to get mushy if it stays for an extended period in the water, and thus it will not last as long as commercial soap. There are ways to extend the life of your bars, and luckily for you, some of these things are already mentioned in the previous list.

But to give you a short overview, it is all the things you use to make your soap harder. These are things like using more harder oils, adding sodium lactate and salt, and stearic acid. All of them do the same thing; they make your soap much more firm and hard.

Just make sure to follow the necessary steps and the correct measurements, as it can quickly go wrong if you don’t know what you’re doing. One final thing I would also suggest is to let your soap cure fully. Soap-making is a patience game. If you can wait long enough, your soap will be firm enough to last long enough.

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