Tips on how to cure handmade soap and ideas for storing it. Curing is the process of allowing saponification to complete and for the soap to fully dry and takes about a month.
Handmade soap needs to cure before you can use or sell it. You may have heard about it before, or done it without understanding why or for how long you should cure different types of soap. I hope to answer those questions in this piece and to provide guidance on exactly how to cure soap, and ways to speed up the process.
Contrary to what other sources may say, you need to cure soap whether you’re using the cold-process or hot-process method. That’s because it’s just as much about letting the bars dry, and form a crystalline structure, as it is about saponification. This piece goes through what’s involved in the curing process, why it’s needed, tips on how to cure your soap faster, and finally how to store your soap when it’s fully cured. If you’re new to soap making, here’s an introduction to making cold-process soap.
Why the need to cure handmade soap?
Even though it looks good to go there are three reasons why you need to cure freshly made soap. Firstly, it’s to allow saponification to complete. Secondly, it’s to let the water content evaporate out and the bars, and for them to dry. Lastly, the longer soap cures, the more chance that the liquid film surrounding each soap molecule has a chance to crystallize. The process is fully explained over here, but all you need to know is that soap’s lather, cleansing ability, and mildness gets better with age.
Saponification is the process where the oils in your recipe are broken apart by, and 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. In hot process soap, saponification is finished by the time you finish the cooking phase but there’s still a lot of water content in the bars. You need to cure the soap to allow it to evaporate off and also to form a microscopic soap crystal structure that will make the soap better to use.
The cure time dries your soap out
When making soap you dissolve the powdered sodium hydroxide (lye) into distilled water, and sometimes a different liquid that will have a water component. That water is still in your bars when you take them out of the mold. If you don’t allow them to cure and dry then your bars will not last once you start using them. They can also have impaired lather.
The cure time will reduce the amount of water in your soap over a period of 4-6 weeks. By the end of that time, your bars can lose over half of the water they originally contained. One way to know that your soap has hit the minimum amount of cure time is to weight the bars each week and to keep a record. Once they stop losing weight, they’re ready to be used.
Unmoulding & cutting handmade soap
I go through explaining this process a lot in my cold-process soap making lessons. That’s one reason that I’m writing this piece — it’s so that I can send the link to my students after a lesson. I hope it can help you too!
If you’ve made cold-process soap, I think it’s best to leave it in the mold for 48 hours. This means that by the time you take it out, the vast majority of the lye has (probably) bonded with the oils. After two days it’s safer to handle and will be harder than it was the day before.
I’d advise wearing 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.
If you’ve used a loaf mold, slice your bars up. This will increase the surface area for drying and cutting fully cured loaves can be more difficult. The size you cut them is up to your personal preference. The soap I sell is about 1″ thick.
How to cure handmade soap
Once your bars are un-molded and sliced it’s time to cure them. There are many places that you can cure your soap but the premise is all the same. It needs an airy place out of direct sunlight. You can use a bookshelf, metal racks, cardboard boxes, stacked milk 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. That’s how it’s been traditionally cured in the Mediterranean and middle east. I’ll pop a video below for you to see how they do it.
Your soap won’t be sopping 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. Again, feel free to stack them, as long as there’s plenty of air that can circulate.
Even if you’ve only made one batch of soap, it pays 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, feel free to 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. Sometimes also if they’re not touching, so keep that in mind. Also, the cure time begins not from the day you made the soap, but from the time you set it on the shelf.
Soap curing time
The time you leave your soap to cure is dependent on the oils and water content of your recipe. Four weeks is a good enough time for the majority of cold-process soap recipes. In hot process soap making, 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 at least 1-3 weeks. Err on the longer side if your bars contain a lot of olive oil (60%+ of a recipe). Castile soap (100% olive oil soap) is harder, milder, and much better quality if you give it at least six weeks to cure — if not a six months to a year.
What happens if I don’t let my soap cure?
There are a few things that can go wrong if you don’t allow your soap to cure. First of all, it could still contain lye. Even though (cold-process) saponification is mainly complete in the first 48 hours, there’s still a chance that your bars will contain lye for up to a month. Lye heavy soap can cause skin irritation and I imagine that there’s a potential for damage if it gets in your eyes.
Curing lets the water content of the soap evaporate out leaving you with harder bars. Soft uncured soap can disintegrate quickly if you get it wet and also have impaired lather. The impaired lather isn’t necessarily from the water content itself but by the way that it affects how the crystalline structure of soap forms during the cure time.
I’ve briefly mentioned curing soap longer so that a more complete crystalline structure can have time to form. It’s a complex chemical process that happens at different rates depending on the fatty acids present in the oil used in your recipe. You don’t need to understand the chemistry of it to make good soap, just remember that the process starts kicking in after most of the excess water in your bars has evaporated out. Young soap bars that are a week or two old can technically be used — both cold-process and hot-process. However, they won’t lather, clean, or last as well as soap that is fully cured or older. The older your soap is, the better it will be.
If you decide to package up uncured soap it could spell disaster too. The moisture can destroy your labels, create condensation under plastic, and otherwise ruin your product.
Ways to cure handmade soap faster
There are a few ways that you can shorten the cure time of soap. The first is to use the water discounting method, which means to use lye solutions with less water. In a standard recipe, you use a 25% lye concentration. For example, if your recipe calls for 100g of lye then you’d make your lye solution with 300g of water (100g is 25% of the total weight of 400g). Making your lye solution stronger, means less water, and a shorter curing time. For most of my recipes, I find that a 35.7% water discount works really well, even for beginners. To get that amount, simply multiply the amount of lye in any soap recipe by 1.8.
The absolute minimum amount of water you can use is equal to the amount of lye in your recipe (a 50% concentration) but this is only advised for advanced soap makers. Creating stronger lye concentrations speeds up how quickly your soap comes to trace and hardens. If you don’t work quickly, it can sometimes become unworkable. It can also affect how evenly your soap gels and cause other issues including cracking.
Another way to cure handmade soap faster is to use a dehumidifier. I keep one going in my workroom when soaps are curing. The time it takes the soap to cure will vary but if you weigh a bar regularly and notice that it’s not losing weight then it’s probably ready. 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.
An electric fan blowing on soap could also reduce your cure time. Again make sure to weigh your soap at the beginning of the cure time and keep an eye on the weight regularly. 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.
Storing handmade soap
Once your soap has fully cured, you’re able to use, gift, or even sell your bars (providing you have your business, insurance, and beauty documentation set up of course). You can also wrap them in paper packaging.
Wrapping them in plastic is a bad idea though for two reasons. First of all, single-use plastic is frowned on these days. There will be customers who won’t want to buy it if there’s anything plastic about it. Secondly, if there’s even the tiniest amount of moisture still in the bars it won’t be able to escape. That means that excess moisture could cause your bars to get Dreaded Orange Spot, literally orange spots on the bars. The spots can get icky and have an unpleasant odor and are an indication that the soap has gone rancid.
The best place to store handmade soap is in the open air. One idea is storing them in a wooden box that also serves as a farmer’s market display. Simply leaving them on the curing rack until they’re needed is also common.
If you’re worried about the natural scent fading, you can also store your soap in a sealed container. However, there are a few things you need to do if you head down this route. The bars should be cured in the open for several months and be bone dry before you put them in. Next, put a few silica gel packets in the container to absorb any moisture. After sealing it, make sure that you open the lid every week or so to air it out. I tend to keep a batch of soap in a plastic bin and then take bars out as I need them, which is pretty regularly.
Just know that keeping them stored like this can become an issue since the bars will have a tendency to sweat. I suspect that it has something to do with the natural glycerin content of the soap — vegetable glycerin is a humectant and can draw moisture from the air.
Shelf-life of handmade soap
This can be easily calculated by looking at all the labels of all the ingredients you used to make soap. The closest best-by date is the best-by date of your new batch of soap. Making soap doesn’t prolong the life of oil about to go off. Using old oil can also cause the Dreaded Orange Spot mentioned before.
Some fresh oils have a shelf-life of up to two years though; coconut oil for example. Make soap with oils that have the longest natural shelf-life and that are well within that best-by date will pay off. It will ensure that your soap will not only last a long time but that you can cure soap for longer, creating better bars, without the fear of them going rancid.
For even more soap making ideas, recipes, and tips head over here.