Curing is the process for which the soap bars finish saponification and dry completely. It takes about a month, in general. Learn how to unmold and cut your cold process soap, readying it for curing, and find out how to cure soap at home.
Table of Contents
- Why Does Your Homemade Soap Need to Cure?
- Do I Need To Cure Hot Process Soap?
- Unmoulding And Cutting Soap
- Cutting Soap Bars
- Use Soap Cutters: It’s Easier
- How to Cure Soap
- How Long Does It Take For Soap To Cure?
- Ways To Cure Handmade Soap Faster
- Curing Melt and Pour Soap?
Why Does Your Homemade Soap Need to Cure?
Even if your soap seems to look good to go after unmoulding it, there are two main reasons why you need to cure freshly made soap:
- First, to allow saponification to complete
- Second, to let the water content evaporate out and the bars to dry
- Third, to allow the soap to harden through crystallization at a molecule level
Saponification is the process where the oils in your recipe bond with the lye. This process is mainly complete in the first 48 hours after you make cold-process soap but the remaining 5% of lye needs more time.
Furthermore, the recipes in this blog use enough water to give time to reach trace and work with the soap. That water is still in your bars when you take them out of the mold. If you don’t allow them to dry then your bars will not last once you start using them. They will turn into a slushy mess in the bath or shower. Soft uncured soap will desintegrate quickly if you get it wet.
Even with water discount (=using less water in lye water) techniques that will speed up cure time, used by more experienced soap makers, it’s still required to give soap time to dry.
The third reason is soap crystallization and this is probably the most difficult to understand, since you don’t actually see it.
Crystallization is the process of forming crystals. Soaps are comprised of solid crystals and a liquid-soap mixture. When soap is first created, it exists in a somewhat “jumbled mess” that undergoes chemical changes to form solid soap crystals, or regularly ordered solidified soap molecules.
Time will allow fatty acids, namely unsaturated fatty acids, to settle down their molecule structure into a more compact one, reducing gaps, kinks and bends between stacked molecules. This will make your soap bar to harden over time.
Crystallization time is not a fixed value. It may vary with several factors such as water/lye concentration, usage of certain addictives and the higher amount of unsaturated fatty acids (basically, liquid oils). It may take six weeks, eight weeks, or even twelve weeks. In fact, the full crystallization process can take months, remember 100% olive oil soap.
So, even if your soap might be minimally ready to be used at 4-6 weeks, it’s always good to let it cure for longer, to allow crystallization to fully develop. Read more about the science behind curing and crystallization in these posts from Classic Bells and The Ultimate Guide to Soap
Do I Need To Cure Hot Process Soap?
Let hot process soap cure for at least 3 to 4 weeks. You need to let soap to cure whether you’re using the cold-process or hot-process method. That’s because curing it’s just as much about letting the bars dry as it is about ending saponification. Curing will allow your soap to improve its soap properties.
Many websites and sources mention that with hot-process there is no need to give time to cure soap, because the temperatures and time during the cooking phase allow the saponification to fully complete.It is true that with cold process, saponification takes time to end, while with hot process, it is done after your are finished cooking your soap. The heat speeds up this whole saponification process in hot process.
However, curing soap has three goals, as we mention before: to finish saponifying, to evaporate excess water, and to develop a crystal structure. And curing is all about having your soap at its best.
Ok, we now know that hot process doesn’t need time to saponify, so the first goal is reached. What about the other two? Allowing your soap bars to dry out the excess of water, you will let them increase in hardness, and become less soluble in water.
The last one is much more complicated to explain, as we are talking about the soap’s molecular structure. Let’s just say that it takes time for the soap crystal molecules to fully stabilize, increasing along with it the soap’s lathering, hardness, longevity, and mildness. Read the whole story, including the chemistry behind these processes, in these posts from Classic Bells and The Ultimate Guide to Soap. It all made sense to me.
Unmoulding And Cutting Soap
Even if you believe that the soap is good to pop out of your mold after a couple of hours, you should leave it for 48 hours in the mold for cold process and 24 hours for hot process. Before that, the soap can be too soft on the sides not exposed to air, and you can easily mark it or even dent it.
After two days cold process is safer to handle, as saponification has most likely happened by then, and will be harder than it was the day before. I’ve almost ruined a couple of soaps with the rush to see how it looks. The soap was too soft and I was destroying its shape. Yes, I feel a bit ashamed…
My advice is to wear gloves for handling your bars at the point of unmoulding. It’s unlikely that you’ll feel anything uncomfortable but there could still be lye in the bars. Touching fresh soap that’s lye-heavy can cause skin dryness and irritation, especially if you have sensitive skin.
Cutting Soap Bars
If you’ve used a loaf mold, slice your bars up to the final size. This will increase the surface area for drying and curing. In addition, cutting fully cured loaves can be much more difficult, and the soap hardens further with time. The loaf will be too hard and soap can break when you cut it. The size you cut them is up to your personal preference.
For 100% olive oil soap, the best is to let it sit for 4 to 7 days. Use only silicone molds with single soaps, avoiding the need to cut them. I am still to find out when/how to cut a loaf of olive oil soap. The last bar I’ve made was very hard and crumbly in the middle and creamy soft in the edges.
Please, be careful as sometimes the loaf soap is soft in the edges, although it’s good to cut in its core.
Use Soap Cutters: It’s Easier
To cut the soap into bars, you can simply use a knife but there’s a good chance of having uneven bars. To have nice rectangular bars, the best way is to purchase a professional cutter. The bars will come out nice and even and you will be able to cut several bars in one go.
If you want a cheaper cutter, use the ones with a wooden box or a wire cutter, all available at Etsy. Some sets also include the soap loaf mold – I’ve bought one of these and am happy with it.
Professional Soap Cutter
Wooden Soap Cutter Box
A wooden soap cutter will be more than enough for you, if you are making soap for yourself. Use the professional one only if you already have a business and need to speed up cutting with a professional finish.
If you’re handy with woodwork, you can make one yourself. There are dozens of videos on YouTube with DIY soap box cutter projects – like this video, for example. But this set is cheap enough and brings the loaf mold as well. You will definitely save time and money, compared with other apparently cheaper solutions.
How to Cure Soap
Once your bars are unmoulded and sliced, it’s now time to cure them. There are many places that you can cure your soap but, basically, it just needs an airy place out of direct sunlight. You can use a bookshelf, metal racks, cardboard boxes, stacked crates, or even make towers of soap.
Stacking soap during curing is perfectly fine and if you live in a warm and arid place, you could even cure your soap outside. I prefer to keep it indoors in a metal rack like this:
Your soap won’t look wet but there will be moisture and it can react with surfaces. Line them with greaseproof or baking paper to protect both your soap and the units you’re using to cure it on/in. Then space your bars out so that there is plenty of airflow around them.
Even if you’ve only made one batch of soap, it’s always better to label it. Mark the date you set them on the shelf and also which soap it is. It could be a batch number or simply the recipe name.
If you have different batches, place them side by side but keep them from touching. If you’ve used different scents, they can affect each other during that long cure time (even if not touching). My unscented oat soap bars became scented with the rose-scented soap curing at their side!
How Long Does It Take For Soap To Cure?
4-6 weeks. That’s the easiest answer. But it depends on the oils and water content of your recipe. 4 weeks is a good enough time for the majority of cold process soap recipes. In hot process, some of the water in the recipe will evaporate off in the cooking process. Not all though. That’s why hot process soap needs to be cured for 3 to 4 weeks as well.
Olive oil soap usually takes longer to set in the mold AND cure. It will make a harder, milder, and much better quality soap bar if you give it at least 8 weeks to cure — if not six months. Some soap recipes using salt take this time to cure, but they make extraordinary and marvelous soap bars. I am yet to make and try them.
By the way, the cure time begins not from the day you made the soap, but from the time you set it on the shelf. Learn everything about curing in this post.
Ways To Cure Handmade Soap Faster
There are a couple of tricks to shorten curing time of soap, although, I repeat, it always needs to cure for some weeks.
The first is to use the water discounting method, which means to use lye solutions with less water – bigger lye concentration. In a standard recipe, you use a 33% lye concentration. For example, if your recipe calls for 33g of lye then you’d make your lye solution with 33g of lye to 67g of water (33g is 33% of 100g). Bringing your lye solution to a 40% concentration can shorten your cure time to just two week
Be aware that a lot of other problems might come up to increasing lye concentration, like soap batter seizing (instantly solidifying) or soap gel happening when you don’t want it, therefore, don’t use it on your own until you’re an experienced soap maker.
Another way to cure handmade soap faster is to use a dehumidifier or an electric fan. You can also cure your soaps outdoors if it’s warm and very dry. Make sure to keep them out of the sun and that they have really good airflow.
The time it takes the soap to cure will vary but if you weight a bar regularly and notice that it’s not losing weight then it’s probably ready. If you’re going to use this method it really helps to know the weight of a fully cured bar of soap. If you’re using the same batch and size as a previous batch weight one of those bars.
Curing Melt and Pour Soap?
If you’re making the soap base at home, the curing time is around 2 to 3 weeks. Well, again, it’s not about – I suppose the added ingredients accelerate the saponification process, pretty much as in hot process with temperature.
But when you’re melting the soap base to make the final soaps with fragrance, colorants, natural addictive and pretty shapes, the soap base is actually ready and doesn’t need to cure.
Hope you have enjoyed this article and found it useful! If you still have a question or want to make a suggestion, please leave a comment below.