Why Does My Soap Crack?

Waking up to see your soap cracks the next day is the worst nightmare for any soap maker. You might still be able to use it, but do you really want to?

Whether you’re seeking a fun hobby, saving money, or pursuing a new business venture, our step-by-step guide makes crafting spa products enjoyable and easy, perfect for hobbies, saving money, or starting a business. Explore 126+ recipes, from soaps to lotions, with our beginner-friendly Quick Start Guide. Ditch store-bought products with unknown chemicals and embrace personalized, high-quality creations that cater to allergies and sensitivities using The Handcrafter’s Companion.

The most frequent cause for soap to crack is due to too high temperature. When the soap gets too hot during the gelling phase, it starts cracking from the top. This is usually caused by the high starting temperature of lye or oils. Also, some sweet ingredients like honey or milk may induce high temperature during the gelling phase.

Why Your Soap Is Cracking:

Closeup yellow candle cut into squares

There may be several reasons for your soap to crack. The good news is most of these common causes can be easily avoided and fixed.

Using Hard Oils Butters and Waxes:

Your batch of homemade soap may crack if there are some flaws in the recipe formulation. Suppose you add a large number of stable oils containing saturated fats like butter and wax. 

Adding butter and waxes such as cocoa butter and beeswax can make the soap hard and brittle because they are solid at room temperature. 

Soap-making experts recommend limiting the number of saturated fats and butter up to 15% of total oils and limiting beeswax to less than 8% of total fat.

Lye heaviness:

Cold process soaps in which lye and oils are combined before the beginning of saponification should have a balanced bar without any leftover lye. When the final product is transformed into soap, it should be a lye balanced product. But if not, it may lead to a crack or oil leakage.

Too much lye results in a heavy lye bar, which is dry and brittle. Excess lye can make the soap crack easily and burn you in the process in case you’re planning on using it. If the soap is crispy, you should check the pH of the soap.


High temperature is arguably the most common reason for soap cracking. When the soap gets too hot in the mold, it rises and cracks. The average soaping temperature is between 110-130 degrees Fahrenheit. When the soap is poured into the mold, it goes through a gel phase in which it gets translucent like a jelly.

The gel phase in a cold process soap refers to how the saponification process occurs. During this process, the soap gets warm and turns gelatinous in the mold. What also happens is that during this phase, the temperature rises to 180 degrees Fahrenheit.

In this process, the soap gets hottest from the center and gradually cools down from the outside. When and if the heat gets slowly released, it expands slightly and cracks on the outside.


Sweet ingredients such as honey, fruit purees, and milk increase cracking during the gel phase. If you are using these ingredients, place the mold in the fridge after pouring for 6-24 hours. 

The soap cracks when dry ingredients are added. They absorb moisture and dry the soap. In this case, it can be dispersed in distilled water. 

For example, if you’re using. Colloidal oatmeal, arrowroot powder, or activated charcoal must use additional water or oil to prevent the soap from becoming dry and brittle.

Can You Still Use Cracked Soap?

There is nothing wrong if your soap gets cracked. It may not look great from an aesthetic standpoint, but it shouldn’t affect the soap’s usability. It remains safe to use if it’s not lye heavy. It’s best to do a pH test to confirm whether the soap is lye heavy or not. However, if your soap broke due to overheating, it is safe to use.

If you are more concerned about usability than aesthetics, you can stir the soap in molds with a spatula. This way, it could evenly distribute the temperature to some extent. 

If the hardening sides are soft, fold the colder areas in the soap’s hot inner side. The soap will then stop expanding and start solidifying in a gelled form inside the mold. Smooth the top with a spatula and let it cool at room temperature without adding insulation. This way, you might still be able to save your soap.

Can It Be Fixed? And How?

In a majority of cases, excessive heating is the main reason for soap cracking. Effective cooling methods can help prevent cracking. 

Spraying alcohol on top:

If your crack is not too deep and big you could still fix it by spraying alcohol on top of it and gently padding it till you don’t see any cracks anymore. As shown in the video below:


Using a fan:

When the soap starts cracking in the mold, immediately removing some heat can fix your problem. If you see that your soap starts cracking in the mold, you should remove all insulation. Then turn the direction of a fan towards the soap mold to increase airflow. 

Put it in the fridge or freezer:

Placing the mold in a fridge or freezer is another effective way of reducing the soap’s temperature immediately. It may settle back down itself, and the crack may disappear in the final product. However, sometimes the damage becomes recognizable and affects the appearance of soap.

Moving it to another mold:

If your soap is rising, you can place it back into the right shape using a spatula. But if the soap has a volcano eruption, then it’s better to scoop out the soap’s overflow into another mold using gloves and a spatula. 

However, if your soap starts erupting, it would be pretty difficult to save it from cracking at this stage. But the soap remains in a usable condition.

How can you prevent cracked soap?

Preventing the soap from cracking requires controlling the factors that lead to its cracking. Here are a few suggestions that will give you more control over your batch.

Controlled Temperatures:

The starting temperature of the lye solution and oils should not be above 90 degrees Fahrenheit. This is the first step in controlling the soap temperature to prevent cracking.

Avoid Insulating the Mold:

Most of the books written by modern pioneers of soap making recommend insulating the mold in the soap making process. However, this practice prevents heat from escaping and results in a cracked soap.

Cooling the Soap in the Fridge or Freezer:

If you are using any oils that produce excessive heat, you should place the mold in the fridge or freezer to remain calm and not crack.

Avoid Adding Sugars:

Avoid adding high amounts of sugars, honey, fruit purees, or any other syrups as they can form a volcano and cause cracking.

Reducing Isopropyl Alcohol:

Minimizing the amount of 91% isopropyl alcohol spray may help in preventing soap from cracking.


Cracking soap in the gel phase affects the look but not always its effectiveness. You can prevent it by making a few changes in your formulations and carefully monitoring temperature in the gel phase. 

In most cases, you can still use a cracked soap but make sure to check pH levels before doing so. 

Recent Posts