Beginner’s Guide to Soapmaking: Cold Process

If you want to customize soap down to the last ingredient, cold process is a great option. You get to choose the oils, colorants, scents, and more. Once you find your perfect recipe you can start getting creative with the designs.

Cold process soap is made by combining oils and sodium hydroxide lye. That causes a chemical reaction called saponification. Melt and pour soap has already gone through that process.

Commonly used terms

Trace: This is the point when the oils and lye water are emulsified. At thin trace, there will be no streaks of oil and the soap will be the consistency of thin cake batter. As the soap sits, it will continue to thicken to medium and thick trace. 

Gel phase: During gel phase, soap gets as hot as 180°F and develops a gelatinous appearance. Gelled soap has a brighter color and a slightly shiny appearance. It can also be unmolded more quickly. Some makers force their soap through gel phase with blankets and heating pads. However, gel phase isn’t required – it’s personal preference. It only affects the look of the bars, not the quality. Ungelled soap has a more matte appearance. You can prevent gel phase by putting soap in the freezer for 24 hours.

Curing: Technically, cold process soap is safe to use after a few days. However, we recommend letting the soap cure for 4-6 weeks in a cool, dry place with good airflow. Excess water will evaporate, which creates harder and milder bars that last longer in the shower. It’s definitely worth the wait.  

Soda ash: This creates an uneven, white, ashy film on soap. It forms when unsaponified lye reacts with naturally-occurring carbon dioxide in the air. It doesn’t affect the quality and the soap is safe to use. However, it can obscure more intricate designs or make the bars feel crumbly. You can prevent it with a few tricks, including a 10% water discount and gel phase.

Lye safety

Lye is a highly corrosive product. It’s safe to use as long as it’s handled properly. Make sure there are no kids, pets, or other distractions in the room when you’re making soap and always do so in a well-ventilated area. You’ll need the following items to work with lye:

Gloves: Rubber dish gloves that go almost to the elbow work great, but they can be bulky. Thinner nitrile or latex gloves provide protection without the bulk. Whatever you choose, they should be paired with long sleeves.

Goggles: Alkali burns are extremely dangerous for your eyes. Your safety goggles should protect them from all sides, so regular glasses aren’t sufficient protection. If you wear glasses, make sure to get goggles that fit over them.

Long sleeves, pants, and close-toed shoes: Protect yourself from unexpected splashes by covering any exposed skin.

Face mask: This is an optional step. If you’re sensitive to lye fumes or if you’re making large batches, you can wear a dust mask.


Any equipment used for soapmaking should be exclusive – don’t use it for food. Lye and fragrance can get stuck in cracks, even with thorough washing. We also recommend hand washing instead of using the dishwasher.

Containers: We recommend heat-safe glass, plastic, or stainless steel bowls. Don’t use aluminum – it can react with the lye and create toxic fumes.

Stick/immersion blender: Using a whisk or stand mixer can take hours. Stick blenders emulsify the soap in just a minute or two, so it’s worth the investment.

Silicone spatulas and spoons: Use these to scrape every last bit of soap out of your container and into the mold. They’re also great for smoothing the top or creating texture.

Scale: For accuracy, all of our soap recipes are measured by weight instead of volume. 

Soap molds: There are plenty of options to choose from. 

  • Silicone molds: These molds are easy to use, unmold, and clean. They’re a great option for beginner and advanced crafters.
  • Wood molds: These are great for large batches and they make it easy to force gel phase. They need to be lined with freezer paper or a silicone liner.
  • Plastic molds: You can use these for cold process, but they do require a few extra steps. We recommend a recipe with lots of hard oils and sodium lactate to help the bars come out cleanly and quickly. 
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