Making homemade soap is a rewarding and addicting hobby, though many new to soap making often question whether their product is up to standards and their ability to make a long-lasting bar of soap.
How long will homemade soap last? If recipes are precisely followed and little to no superfat percentage is used, homemade soap can last for years, with a shelf life similar to that of commercial products. A long shelf life will depend on the oils used, curing environment, and storing practices.
The shelf life of soap really depends on a number of factors, and the best way to ensure that you’re making a long-lasting soap is to examine each one carefully.
Let’s get started.
How Long Will Homemade Soap Last?
Generally, the harder and drier a soap is, the longer it will last.
Once a batch has saponified, it is soap and will technically remain soap for many years. In fact, the older the soap is, the better it seems to perform in the shower.
However, some qualities may begin to decline slightly with time.
Will the soap last indefinitely? Well, it really depends on several factors.
Before we dive into them, I should clarify that, here, I’ll be focusing on cold process soaping, the most popular method of creating homemade bars.
What You Might Notice
Once your soap has cured for the recommended six weeks, you may notice several changes either right away or as time passes:
- Color and scent may fade slightly.
- A white or light gray powder forms on the surface.
- Strange orange spots might appear, usually along outside edges.
- Small drops of moisture may be present.
These changes are all merely cosmetic, and the soap is still fine to use in most cases; however, if you plan on selling your soaps one day, these issues could be a problem.
On the other hand, your soap may hold up extremely well for several years.
Color, Fragrance, and Soda Ash
The fading of color and scents won’t affect the soap’s shelf life at all.
If natural colorants were used, the soap may turn lighter over time, especially if exposed to direct sunlight.
Some mica colorants will morph or fade, others won’t.
Soap scented with only essential oil usually doesn’t hold the scent for long, as EOs are volatile and will break down during saponification or will evaporate during cure. Find out more about essential oils in soap here.
Many fragrance oils will stay true to their scent for a very long time while others will disappear in just a few months.
Soda ash (a whitish powder) can form when soap was created using oils and lye that were cooler than 100 degrees Fahrenheit, when soap was poured at thin trace, or when soap was cured in a cold room.
The powdery substance occurs when the unsaponified lye reacts with carbon dioxide in the air. While not pleasant to find, soda ash is harmless and can be wiped off with a damp rag.
The other changes involving spots and moisture droplets are deeper issues that may negatively affect the shelf life of your hard work.
Let’s take a look at what causes these changes to occur and how they affect the quality and usability of the soap.
Factors That Impact the Shelf Life of Homemade Soap
There are many variables that can influence how long your soap will stay pristine and fresh.
That’s why it is best to avoid shortcuts when making soap. You really want to focus on each stage of the process to ensure good results.
Soap makers use all kinds of oils to mix with the lye solution to make soap.
It’s well known that different oils have different properties, but you may not know that they also have different shelf lives.
Some oils, like flax seed oil, only stay fresh for 6 months to 1 year while others, such as jojoba oil, may keep longer than 2 years.
Oils that have undergone saponification won’t turn rancid or affect the soap negatively at all because they have combined with the lye molecules to form soap.
However, many soap makers add a little extra oil to their recipe for added moisturizing.
This is known as superfatting, and while it does produce a luxurious soap, there will be “leftover” oil after saponification.
That remaining oil could turn rancid and cause what is known as dreaded orange spots (DOS for short), the bane of every soap maker.
DOS soaps are generally okay to use unless there’s an unpleasant smell, in which case the soap should be thrown away.
Oils that are solid at room temperature, such as coconut oil or palm oil, help to produce a hard soap bar with an extended shelf life as opposed to softer oils like olive oil, which produce a softer bar that won’t last as long.
Temperature and Humidity
High temperatures can cause soap to melt, obviously decreasing the shelf life, and extremely cold temperatures cause soap to become brittle.
While temperatures can also be a factor in the formation of soda ash, a bigger problem, however, is high humidity.
During cure time, the water from the lye solution slowly evaporates, leaving behind a nice, hard soap bar.
If there’s lots of moisture in the air (humidity), the water won’t evaporate, external water droplets may form, the soap won’t harden properly, and shelf life will be decreased.
Humidity also contributes to those horrible orange spots. Homemade soap contains wonderfully moisturizing glycerin, a natural humectant.
Glycerin actually draws moisture from the air, encouraging remaining oils to turn rancid and causing soap to become softer – great ways to decrease shelf life.
Tips For Making a Long-Lasting Homemade Soap
With time and practice, you’ll learn what works best for your favorite soap recipe.
Until you get to that point, there are several options that you can experiment with to achieve a long-lasting bar of soap that holds on to its color, scent, and beauty.
One secret to making a hard, long-lasting soap is to add sodium lactate, a liquid salt, to the lye water once it has cooled to between 120 and 130 degrees.
It makes unmolding and cutting the soap a breeze and produces a nice, hard bar. Recommended use calls for 1 teaspoon per pound of oils.
While soap doesn’t need any added preservatives because the pH levels naturally guard against the growth of mold and bacteria, many soapers like to include additives with preserving properties to help extend the life of the oils in soap.
Try adding the following at about 10 drops per pound of soap:
- Vitamin E oil.
- Grapefruit seed extract (not the same as grapefruit essential oil).
- Rosemary oil extract (also known as rosemary oleoresin).
Spritzing the top of the soap with isopropyl alcohol after you pour it into the mold can help prevent soda ash from forming.
Water discounting is simply cutting back on the amount of water used to make the lye solution. A 10% discount is usually a good place to start.
Water discounting will cause the soap to cure more quickly, resulting in a harder bar sooner, and may help prevent soda ash.
Also, be sure to only use distilled water. The minerals in tap water can contribute to DOS.
Run your recipe through an online soap calculator to be sure your lye to oil ratios will produce a hard bar with little leftover oil.
To avoid the rapid appearance of DOS, you’ll want to superfat below 5%.
Cure and Store Properly
Allow each batch to cure in a cool, dry room for at least six weeks. Running a dehumidifier can help.
A baker’s rack with coated metal is ideal for curing and storing soap as it allows for maximum air circulation.
- Allow the bars to touch.
- Store differently scented soaps together.
- Store soaps in an air-tight container.
How Long Will Homemade Soap Last Once You Start Using It?
Of course, the more the soap is used, the faster it will disappear. Allowing the soap to dry thoroughly after each use will definitely help it last longer.
Use a soap dish that allows plenty of air to circulate all around the bar to encourage drying.