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My Reward PointsAfter pouring soap into the mold, you may discover cracks forming overnight. This blog identifies common reasons for such fractures in soap batches, aiming to explain the potential causes behind the soap cracking.
What is Bar Soap Cracking?
Bar soap cracking occurs when changes in moisture content lead to surface fatigue, resulting in visible lines or crevices. Because bar soap is used in damp environments, moisture fluctuations are unavoidable, so this phenomenon is common.
8 Reasons of Soap Cracking
Soap and syndet bars crack due to moisture absorption, poor curing, high oil content, or rapid temperature changes, causing expansion, contraction, or drying stress. Here are some reasons that contribute to soap cracking.
1. The Soap Cuts Too Early
Cutting soap too early or handling it roughly—especially when soft, wet, or lye-heavy—can cause dents, drag marks, or cracks, making it more vulnerable to physical damage.
Cause
Cutting soap too soon results in breaking because the soap is not yet solid enough to maintain its shape under pressure from a knife or cutting wire.
Solution
Use a sharp, flat blade to cut when hard yet slightly soft to avoid soap splitting and For consistent results, use a cutting box and place bars on a drying rack.
2. Too Much Water in the Recipe
Excess water in soap batter can lead to cracking as it evaporates and shrinks, while incorrect lye levels may create an unbalanced composition, resulting in structural weaknesses and cracks.
Cause
Excessive water in a soap making recipe can cause overheating during saponification, leading to cracking from temperature fluctuations, as well as glycerin rivers and surface irregularities.
Solution
Most soap recipe calculators use a default of 38% water relative to oils, meaning for every 100 grams (or ounces) of fats, there are 38 grams (or ounces) of water.
3. Rapid Cooling After Pouring
Cracking in cold-process soap occurs due to rapid cooling, where the outer layers solidify quickly. Sudden temperature fluctuations, such as heating or cooling too quickly, might cause the soap to break.
Cause
Soap may crack if it cools rapidly after being poured, due to temperature imbalances caused by the exothermic saponification reaction between lye and oils.
Solution
During pouring, prevent homemade soap cracking by maintaining stable temperatures—remove insulation, lower room heat, and use gentle airflow. Use a spatula to smooth out any soft cracks, and use ice packs or refrigeration to cool down delicate soaps.
4. Overheating During Saponification
Overheating in saponification can cause surface cracks in cold-process soap, particularly in recipes with high temperatures and ingredients like milk, sugars, and certain oils.
Cause
Overheating soap during saponification can cause surface cracks and uneven solidification, with factors like insulation and sugar-rich oil ingredients exacerbating the exothermic reaction and increasing damage risk.
Solution
Using warm oils, lye water, and insulation encourages a consistent gel phase, that prevent soap cracks. Avoid overheating, especially when using milk or sugar additives, but maintain constant temperatures.
5. Inconsistent or Improper Curing Conditions
One of the main causes of handmade soap cracking is irregular or inappropriate curing conditions. The most common causes of the problem includes variations in temperature and unequal water evaporation.
Cause
Uneven drying leads to physical stress and cracks in soap, caused by inconsistent curing conditions. Additionally, poor temperature management may result in overheating or incomplete reactions during saponification.
Solution
To prevent cracking in the soap-making process, reduce insulation, use less water, and avoid components that can cause overheating, while also, ensure careful handling and adequate air circulation for proper curing.
6. Too Much Fragrance Oil or Additives
Soap can fracture if fragrance oil or specific ingredients are used in excess. This problem frequently has to do with how the ingredients impact the temperature, texture, or saponification process of the soap.
Cause
Excess fragrance oil accelerates saponification, causing heat buildup, rapid thickening, and internal cracks. Floral, spicy, or alcohol-rich fragrance oils increase the risk of splitting due to uneven temperature stress.
Solution
Use limited hard oils, butters, or waxes, and only 3% fragrance oil (0.5–1 oz per pound). Cracks occur from improper ratios, overheating, temperature shifts, or excess fragrance oil.
7. Too High of a Superfat
Soap cracking mainly results from overheating and excess hard oils, butters, or sugar. High superfat doesn’t cause cracks but can make soap softer, reduce lather, and increase spoilage risk.
Cause
High superfat content in soap can cause cracking due to excess unsaponified oils and overheating, leading to an oily, brittle, or squishy texture instead of a firm bar.
Solution
Handcrafted cold process soap should typically use 5–8% superfat to help prevent cracking, though cracks mainly result from heat during saponification, not superfatting alone.
8. Using Cold Oils or Lye Solution
Cold process soap cracking may occur from cold oils or overly hot lye. High heat causes gel-phase splitting, while low temperatures create false trace, producing brittle, easily broken soap.
Cause
A dry, brittle bar may be an indication of cold oils and too much lye in the recipe; soap containing hard oils, butters, milk, or honey may split when heated during the gel phase.
Solution
Aim for a temperature differential of 10 to 15 degrees between oils and lye, not exceeding 100°F (38°C) to avoid soap breaking. Temperatures above 120°F may accelerate soaping, while 80°F to 120°F is permissible.
Conclusion
There is a problem of cracked soap bars during the saponification in soap making and unmolding process. Understanding the above reasons and applying preventive actions will help you reduce the danger of soap cracking during the saponification process and create high-quality cold-process soaps.
